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Slusher GA, Kottke PA, Culberson AL, Chilmonczyk MA, Fedorov AG. Microfluidics enabled multi-omics triple-shot mass spectrometry for cell-based therapies. Biomicrofluidics 2024; 18:011302. [PMID: 38268742 PMCID: PMC10807926 DOI: 10.1063/5.0175178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 01/01/2024] [Indexed: 01/26/2024]
Abstract
In recent years, cell-based therapies have transformed medical treatment. These therapies present a multitude of challenges associated with identifying the mechanism of action, developing accurate safety and potency assays, and achieving low-cost product manufacturing at scale. The complexity of the problem can be attributed to the intricate composition of the therapeutic products: living cells with complex biochemical compositions. Identifying and measuring critical quality attributes (CQAs) that impact therapy success is crucial for both the therapy development and its manufacturing. Unfortunately, current analytical methods and tools for identifying and measuring CQAs are limited in both scope and speed. This Perspective explores the potential for microfluidic-enabled mass spectrometry (MS) systems to comprehensively characterize CQAs for cell-based therapies, focusing on secretome, intracellular metabolome, and surfaceome biomarkers. Powerful microfluidic sampling and processing platforms have been recently presented for the secretome and intracellular metabolome, which could be implemented with MS for fast, locally sampled screening of the cell culture. However, surfaceome analysis remains limited by the lack of rapid isolation and enrichment methods. Developing innovative microfluidic approaches for surface marker analysis and integrating them with secretome and metabolome measurements using a common analytical platform hold the promise of enhancing our understanding of CQAs across all "omes," potentially revolutionizing cell-based therapy development and manufacturing for improved efficacy and patient accessibility.
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Affiliation(s)
| | - Peter A. Kottke
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30318, USA
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2
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Culberson AL, Bowles-Welch AC, Wang B, Kottke PA, Jimenez AC, Roy K, Fedorov AG. Early detection and metabolic pathway identification of T cell activation by in-process intracellular mass spectrometry. Cytotherapy 2023; 25:1006-1015. [PMID: 37061898 PMCID: PMC10524195 DOI: 10.1016/j.jcyt.2023.03.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 03/15/2023] [Accepted: 03/20/2023] [Indexed: 04/17/2023]
Abstract
BACKGROUND AIMS In-process monitoring and control of biomanufacturing workflows remains a significant challenge in the development, production, and application of cell therapies. New process analytical technologies must be developed to identify and control the critical process parameters that govern ex vivo cell growth and differentiation to ensure consistent and predictable safety, efficacy, and potency of clinical products. METHODS This study demonstrates a new platform for at-line intracellular analysis of T-cells. Untargeted mass spectrometry analyses via the platform are correlated to conventional methods of T-cell assessment. RESULTS Spectral markers and metabolic pathways correlated with T-cell activation and differentiation are detected at early time points via rapid, label-free metabolic measurements from a minimal number of cells as enabled by the platform. This is achieved while reducing the analytical time and resources as compared to conventional methods of T-cell assessment. CONCLUSIONS In addition to opportunities for fundamental insight into the dynamics of T-cell processes, this work highlights the potential of in-process monitoring and dynamic feedback control strategies via metabolic modulation to drive T-cell activation, proliferation, and differentiation throughout biomanufacturing.
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Affiliation(s)
- Austin L Culberson
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA; National Science Foundation Engineering Research Center (ERC) for Cell Manufacturing Technologies (CMaT), Atlanta, Georgia, USA
| | - Annie C Bowles-Welch
- Marcus Center for Therapeutic Cell Characterization and Manufacturing, Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Bryan Wang
- National Science Foundation Engineering Research Center (ERC) for Cell Manufacturing Technologies (CMaT), Atlanta, Georgia, USA; Marcus Center for Therapeutic Cell Characterization and Manufacturing, Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA; The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, USA; School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Peter A Kottke
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Angela C Jimenez
- National Science Foundation Engineering Research Center (ERC) for Cell Manufacturing Technologies (CMaT), Atlanta, Georgia, USA; Marcus Center for Therapeutic Cell Characterization and Manufacturing, Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA; The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, USA
| | - Krishnendu Roy
- National Science Foundation Engineering Research Center (ERC) for Cell Manufacturing Technologies (CMaT), Atlanta, Georgia, USA; Marcus Center for Therapeutic Cell Characterization and Manufacturing, Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, USA; The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, Georgia, USA
| | - Andrei G Fedorov
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA; National Science Foundation Engineering Research Center (ERC) for Cell Manufacturing Technologies (CMaT), Atlanta, Georgia, USA.
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Sung D, Rejimon A, Allen JW, Fedorov AG, Fleischer CC. Predicting brain temperature in humans using bioheat models: Progress and outlook. J Cereb Blood Flow Metab 2023; 43:833-842. [PMID: 36883416 PMCID: PMC10196749 DOI: 10.1177/0271678x231162173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 01/31/2023] [Accepted: 02/02/2023] [Indexed: 03/09/2023]
Abstract
Brain temperature, regulated by the balance between blood circulation and metabolic heat generation, is an important parameter related to neural activity, cerebral hemodynamics, and neuroinflammation. A key challenge for integrating brain temperature into clinical practice is the lack of reliable and non-invasive brain thermometry. The recognized importance of brain temperature and thermoregulation in both health and disease, combined with limited availability of experimental methods, has motivated the development of computational thermal models using bioheat equations to predict brain temperature. In this mini-review, we describe progress and the current state-of-the-art in brain thermal modeling in humans and discuss potential avenues for clinical applications.
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Affiliation(s)
- Dongsuk Sung
- Department of Biomedical
Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA,
USA
- Department of Radiology and Imaging
Sciences, Emory University School of Medicine, Atlanta, GA, USA
| | - Abinand Rejimon
- Department of Biomedical
Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA,
USA
- Department of Radiology and Imaging
Sciences, Emory University School of Medicine, Atlanta, GA, USA
| | - Jason W Allen
- Department of Biomedical
Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA,
USA
- Department of Radiology and Imaging
Sciences, Emory University School of Medicine, Atlanta, GA, USA
- Department of Neurology, Emory
University School of Medicine, Atlanta, GA, USA
| | - Andrei G Fedorov
- Woodruff School of Mechanical
Engineering, Georgia Institute of Technology, Atlanta, GA, USA
- Petit Institute for Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
| | - Candace C Fleischer
- Department of Biomedical
Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA,
USA
- Department of Radiology and Imaging
Sciences, Emory University School of Medicine, Atlanta, GA, USA
- Petit Institute for Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
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4
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Sung D, Risk BB, Kottke PA, Allen JW, Nahab F, Fedorov AG, Fleischer CC. Comparisons of healthy human brain temperature predicted from biophysical modeling and measured with whole brain MR thermometry. Sci Rep 2022; 12:19285. [PMID: 36369468 PMCID: PMC9652378 DOI: 10.1038/s41598-022-22599-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2022] [Accepted: 10/17/2022] [Indexed: 11/13/2022] Open
Abstract
Brain temperature is an understudied parameter relevant to brain injury and ischemia. To advance our understanding of thermal dynamics in the human brain, combined with the challenges of routine experimental measurements, a biophysical modeling framework was developed to facilitate individualized brain temperature predictions. Model-predicted brain temperatures using our fully conserved model were compared with whole brain chemical shift thermometry acquired in 30 healthy human subjects (15 male and 15 female, age range 18-36 years old). Magnetic resonance (MR) thermometry, as well as structural imaging, angiography, and venography, were acquired prospectively on a Siemens Prisma whole body 3 T MR scanner. Bland-Altman plots demonstrate agreement between model-predicted and MR-measured brain temperatures at the voxel-level. Regional variations were similar between predicted and measured temperatures (< 0.55 °C for all 10 cortical and 12 subcortical regions of interest), and subcortical white matter temperatures were higher than cortical regions. We anticipate the advancement of brain temperature as a marker of health and injury will be facilitated by a well-validated computational model which can enable predictions when experiments are not feasible.
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Affiliation(s)
- Dongsuk Sung
- grid.213917.f0000 0001 2097 4943Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA USA
| | - Benjamin B. Risk
- grid.189967.80000 0001 0941 6502Department of Biostatistics and Bioinformatics, Emory University, Atlanta, GA USA
| | - Peter A. Kottke
- grid.213917.f0000 0001 2097 4943Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA USA
| | - Jason W. Allen
- grid.213917.f0000 0001 2097 4943Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA USA ,grid.189967.80000 0001 0941 6502Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA USA ,grid.189967.80000 0001 0941 6502Department of Neurology, Emory University School of Medicine, Atlanta, GA USA
| | - Fadi Nahab
- grid.189967.80000 0001 0941 6502Department of Neurology, Emory University School of Medicine, Atlanta, GA USA
| | - Andrei G. Fedorov
- grid.213917.f0000 0001 2097 4943Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA USA ,grid.213917.f0000 0001 2097 4943Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA USA
| | - Candace C. Fleischer
- grid.213917.f0000 0001 2097 4943Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA USA ,grid.189967.80000 0001 0941 6502Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA USA ,grid.213917.f0000 0001 2097 4943Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA USA ,grid.189967.80000 0001 0941 6502Wesley Woods Health Center, Emory University School of Medicine, 1841 Clifton Road, Atlanta, GA 30329 USA
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Kucuktas OA, Kottke PA, Simeroth DL, Fedorov AG. Altering apparent optical properties with an array of semitransparent mesoscale structures. J Opt Soc Am A Opt Image Sci Vis 2022; 39:1569-1576. [PMID: 36215623 DOI: 10.1364/josaa.463155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 07/18/2022] [Indexed: 06/16/2023]
Abstract
The ability to control and optimize interactions between light and matter has much utility in engineering design. A well-researched way to achieve optical property modulation is via the use of optical metamaterials, which feature sub-wavelength scale surface structures. In this work, an alternative approach for modulating optical properties is presented using a composite surface modified with a periodic array of semitransparent hemispherical shell mesoscale structures which are larger than the incident light wavelength. A ray-tracing simulation approach is used to predict the optical behavior for an arrayed surface. At oblique angles of incidence, significant increases and decreases in apparent absorptance are achieved via the use of optically thick and thin shells, respectively. Additionally, a potential application to solar cells is described with optimal spectral behavior achieved via the use of semitransparent external structures.
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Prabhakaran V, Romo J, Bhattarai A, George K, Norberg ZM, Kalb D, Aprà E, Kottke PA, Fedorov AG, El-Khoury PZ, Johnson GE, Laskin J. Integrated photoelectrochemical energy storage cells prepared by benchtop ion soft landing. Chem Commun (Camb) 2022; 58:9060-9063. [PMID: 35899861 PMCID: PMC9367248 DOI: 10.1039/d2cc02595g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The exceptional photochromic and redox properties of polyoxometalate anions, PW12O403−, have been exploited to develop an integrated photoelectrochemical energy storage cell for conversion and storage of solar energy. Elimination of strongly coordinating cations using benchtop ion soft landing leads to a ∼370% increase in the maximum power output of the device. Additionally, the photocathode displayed a pronounced color change from clear to blue upon irradiation, which warrants the potential application of the IPES cell in advanced smart windows and photochromic lenses. Soft landing eliminates counter cations from Keggin polyoxometalate-based photocathodes, resulting in a ∼370% increase in maximum power output from a novel device that simultaneously harvests and stores solar energy.![]()
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Affiliation(s)
| | - Joelle Romo
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
| | - Ashish Bhattarai
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
| | - Kyle George
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
| | - Zachary M Norberg
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
| | - David Kalb
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
| | - Edoardo Aprà
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
| | - Peter A Kottke
- School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Andrei G Fedorov
- School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Patrick Z El-Khoury
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
| | - Grant E Johnson
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
| | - Julia Laskin
- Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA.
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7
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Ahmed A, Boyle EC, Kottke PA, Fedorov AG. Radiolytic redox interplay defines nanomaterial synthesis in liquids. Sci Adv 2021; 7:eabj8751. [PMID: 34919426 PMCID: PMC8682990 DOI: 10.1126/sciadv.abj8751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 11/02/2021] [Indexed: 06/14/2023]
Abstract
Irradiation of a liquid solution generates solvated electrons and radiolysis products, which can lead to material deposition or etching. The chemical environment dictates the dominant reactions. Radiolysis-induced reactions in salt solutions have substantially different results in pure water versus water-ammonia, which extends the lifetime of solvated electrons. We investigate the interplay between transport and solution chemistry via the example of solid silver formation from e-beam irradiation of silver nitrate solutions in water and water-ammonia. The addition of ammonia results in the formation of a secondary ring-shaped deposit tens of micrometers in diameter (formed over tens of seconds) around the primary point of deposition (formed over milliseconds). Simulations uncover the relative importance of oxidizing and reducing reactions and transport effects. Our explanation of this behavior involves mechanisms beyond ammonia’s role in extending solvated electron lifetimes.
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8
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Culberson AL, Chilmonczyk MA, Kottke PA, Bowles-Welch AC, Ghoshal D, Fedorov AG. Sample-to-analysis platform for rapid intracellular mass spectrometry from small numbers of cells. Lab Chip 2021; 21:4696-4706. [PMID: 34751694 PMCID: PMC8721559 DOI: 10.1039/d1lc00884f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Real-time, advanced diagnostics of the biochemical state within cells remains a significant challenge for research and development, production, and application of cell-based therapies. The fundamental biochemical processes and mechanisms of action of such advanced therapies are still largely unknown, including the critical quality attributes that correlate to therapeutic function, performance, and potency and the critical process parameters that impact quality throughout cell therapy manufacturing. An integrated microfluidic platform has been developed for in-line analysis of a small number of cells via direct infusion nano-electrospray ionization mass spectrometry. Central to this platform is a microfabricated cell processing device that prepares cells from limited sample volumes removed directly from cell culture systems. The sample-to-analysis workflow overcomes the labor intensive, time-consuming, and destructive nature of existing mass spectrometry approaches for analysis of cells. By providing rapid, high-throughput analyses of the intracellular state, this platform enables untargeted discovery of critical quality attributes and their real-time, in-process monitoring.
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Affiliation(s)
- Austin L Culberson
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
| | - Mason A Chilmonczyk
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
| | - Peter A Kottke
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
| | - Annie C Bowles-Welch
- Marcus Center for Therapeutic Cell Characterization and Manufacturing, Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, USA
| | - Delta Ghoshal
- The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Andrei G Fedorov
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
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9
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Chilmonczyk MA, Doron G, Kottke PA, Culberson AL, Leguineche K, Guldberg RE, Horwitz EM, Fedorov AG. Localized Sampling Enables Monitoring of Cell State via Inline Electrospray Ionization Mass Spectrometry. Biotechnol J 2021; 16:e2000277. [PMID: 32975016 PMCID: PMC7940552 DOI: 10.1002/biot.202000277] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 09/09/2020] [Indexed: 12/21/2022]
Abstract
Nascent advanced therapies, including regenerative medicine and cell and gene therapies, rely on the production of cells in bioreactors that are highly heterogeneous in both space and time. Unfortunately, advanced therapies have failed to reach a wide patient population due to unreliable manufacturing processes that result in batch variability and cost prohibitive production. This can be attributed largely to a void in existing process analytical technologies (PATs) capable of characterizing the secreted critical quality attribute (CQA) biomolecules that correlate with the final product quality. The Dynamic Sampling Platform (DSP) is a PAT for cell bioreactor monitoring that can be coupled to a suite of sensor techniques to provide real-time feedback on spatial and temporal CQA content in situ. In this study, DSP is coupled with electrospray ionization mass spectrometry and direct-from-culture sampling to obtain measures of CQA content in bulk media and the cell microenvironment throughout the entire cell culture process (≈3 weeks). Post hoc analysis of this real-time data reveals that sampling from the microenvironment enables cell state monitoring (e.g., confluence, differentiation). These results demonstrate that an effective PAT should incorporate both spatial and temporal resolution to serve as an effective input for feedback control in biomanufacturing.
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Affiliation(s)
- Mason A. Chilmonczyk
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia
- NSF Engineering Research Center (ERC) for Cell Manufacturing Technologies (CMaT), Parker H. Petit Institute for Bioengineering & Biosciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Gilad Doron
- NSF Engineering Research Center (ERC) for Cell Manufacturing Technologies (CMaT), Parker H. Petit Institute for Bioengineering & Biosciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Peter A. Kottke
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia
- NSF Engineering Research Center (ERC) for Cell Manufacturing Technologies (CMaT), Parker H. Petit Institute for Bioengineering & Biosciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Austin L. Culberson
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia
- NSF Engineering Research Center (ERC) for Cell Manufacturing Technologies (CMaT), Parker H. Petit Institute for Bioengineering & Biosciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Kelly Leguineche
- The Phil and Penny Knight Campus for Accelerating Scientific Impact, University of Oregon, Eugene, OR
| | - Robert E. Guldberg
- NSF Engineering Research Center (ERC) for Cell Manufacturing Technologies (CMaT), Parker H. Petit Institute for Bioengineering & Biosciences, Georgia Institute of Technology, Atlanta, Georgia
- The Phil and Penny Knight Campus for Accelerating Scientific Impact, University of Oregon, Eugene, OR
| | | | - Andrei G. Fedorov
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia
- NSF Engineering Research Center (ERC) for Cell Manufacturing Technologies (CMaT), Parker H. Petit Institute for Bioengineering & Biosciences, Georgia Institute of Technology, Atlanta, Georgia
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Kim S, Fedorov AG. FEBIP for functional nanolithography of 2D nanomaterials. Nanofabrication 2020. [DOI: 10.1088/978-0-7503-2608-7ch12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Lee JY, Kottke PA, Fedorov AG. Electrohydrodynamics of Gas-Assisted Electrospray Ionization Mass Spectrometry. J Am Soc Mass Spectrom 2020; 31:2073-2085. [PMID: 32869991 DOI: 10.1021/jasms.0c00197] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Gas-flow assistance is commonly used in ESI-MS for improved transport and desolvation, and fundamental understanding of the underlying phenomena is essential for improvement of aerodynamic interfaces that couple ESI sources and MS. For this purpose, an electrohydrodynamic model is developed for simulation of charged droplet dynamics under the combined effects of gas flow and electric fields with consideration of space charge interactions within the charged aerosol plume. The model is implemented in COMSOL by exploiting a formalism for establishing the droplet trajectories as a sequence of successive droplets ejected at a frequency defined by the electrospray current. The model is used to assess the effect of two distinct flow configurations and compared to the baseline care of electrospray without assist gas. The simulated flows are jet flows oriented coaxially with the ESI spray, with and without imposed vorticity (swirling). Droplet trajectory simulations of a bimodal droplet population consisting of large primary droplets and small progeny droplets reveal a unique capability for vortical assist jet flow to selectively transmit smaller droplets into the MS due to inertial separation. ESI-MS analysis of fluorinated phosphazines subjected to the different gas flow conditions supports the model predictions. The electrohydrodynamic model developed in this work provides a versatile tool to analyze and design aerodynamic ESI interfaces with rigorous incorporation of drag, inertia, and space-charge repulsion and can be used as a powerful simulation methodology for optimizing charged droplet transmission and ultimately improved analytical performance of gas-assisted ESI-MS workflows.
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Affiliation(s)
- Jung Y Lee
- G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Peter A Kottke
- G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Andrei G Fedorov
- G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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Lee JY, Kottke PA, Fedorov AG. Hydrodynamics of Vortical Gas Jets Coupled to Point-Like Suction. Phys Fluids (1994) 2020; 32:103602. [PMID: 33184554 PMCID: PMC7656120 DOI: 10.1063/5.0019840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 09/14/2020] [Indexed: 06/11/2023]
Abstract
Vortical jet flows in the Reynolds number (Re) range from 1000 to 3425 and swirl number (S) below 0.5, alone and in combination with suction through a small aperture, are experimentally investigated using optical visualization. Schlieren photography is employed to assess the vortical flow structure and establish the fundamental understanding of the source-to-sink gas-dynamic coupling, including the role played by flow rate, jet diameter, and the separation distance between the gas jet source and the suction sink. Compared to vortex-free jets, vortical jets for Re>2700 with swirl number S>0.27 experience earlier laminar-to-turbulent transition, with resulting rapid growth of the jet boundary. The ability to control growth of the jet expansion and mass and momentum dissipation into the surrounding is demonstrated via use of a coaxially aligned flow suction placed in the path of a jet. When a swirling jet is completely coupled with a flow suction, jet expansion is significantly suppressed. The suction/sink flow rate imposes a limit on the maximum input/source flow rate of gas jet to achieve complete coupling. Furthermore, there is a maximum distance over which effective coupling can occur, and for all Reynolds numbers considered this distance is shorter than the distance at which the jet structure breaks up into turbulent eddies in the absence of a sink.
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Affiliation(s)
- Jung Y. Lee
- G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Peter A. Kottke
- G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Andrei G. Fedorov
- G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia USA
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Kim S, Jung S, Lee J, Kim S, Fedorov AG. High-Resolution Three-Dimensional Sculpting of Two-Dimensional Graphene Oxide by E-Beam Direct Write. ACS Appl Mater Interfaces 2020; 12:39595-39601. [PMID: 32805878 DOI: 10.1021/acsami.0c11053] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
On-demand switchable "additive/subtractive" patterning of two-dimensional (2D) nanomaterials is an essential capability for developing new concepts of functional nanomaterials and their device realizations. Traditionally, this is performed via a multistep process using photoresist coating and patterning by conventional photo or electron beam lithography, which is followed by bulk dry/wet etching or deposition. This limits the range of functionalities and structural topologies that can be achieved as well as increases the complexity, cost, and possibility of contamination, which are significant barriers to device fabrication from highly sensitive 2D materials. Focused electron beam-induced processing (FEBIP) enables a material chemistry/site-specific, high-resolution multimode atomic scale processing and provides unprecedented opportunities for "direct-write", single-step surface patterning of 2D nanomaterials with an in situ imaging capability. It allows for realizing a rapid multiscale/multimode approach, ranging from an atomic scale manipulation (e.g., via targeted defect introduction as an active site) to a large-area surface modification on nano- and microscales, including patterned doping and material removal/deposition with 2D (in-plane)/three-dimensional (3D) (out-of-plane) control. In this work, we report on a new capability of FEBIP for nanoscale patterning of graphene oxide via removal of oxygenated carbon moieties with no use of reactive gas required for etching complemented by carbon atom deposition using a focused electron beam. The mechanism of experimentally observed phenomena is explored using the density functional theory (DFT) calculations, revealing that interactions of e-beam that liberated reactive oxygen radicals with carbon atoms on the graphene basal plane lead to the creation of atomic vacancies in the material. The reaction byproducts are volatile carbon dioxides, which are dissociated and volatilized from the graphene oxide surface functional groups by interactions with an energetic focused electron beam. Along with selective subtractive patterning of graphene oxide, the same electron beam with increased irradiation doses can deposit out-of-plane 3D carbon nanostructures on top of or around the 2D etched pattern, thus forming a hybrid 2D/3D nanocomposite with a feature control down to a few nanometers. This in operando dual nanofabrication capability of FEBIP is unmatched by any other nanopatterning techniques and opens a new design window for forming 2D/3D complex nanostructures and functional nanodevices.
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Affiliation(s)
- Songkil Kim
- School of Mechanical Engineering, Pusan National University, Busan 46241, South Korea
| | - SungYeb Jung
- Department of Physics, Pusan National University, Busan 46241, South Korea
| | - Jaekwang Lee
- Department of Physics, Pusan National University, Busan 46241, South Korea
| | - Seokjun Kim
- School of Mechanical Engineering, Pusan National University, Busan 46241, South Korea
| | - Andrei G Fedorov
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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14
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Abstract
A new state of radical thermal non-equilibrium in surface adsorbed molecules is discovered that enables rapid surface diffusion of energized adatoms with a negligible effect on the substrate surface temperature. Due to enhanced surface diffusion, growth rates can be achieved that improve the feasibility of many nanofabrication techniques. Since the adatom temperature cannot be directly measured without disturbing its thermodynamic state, the first principle hard-cube model is used to predict both the adatom effective temperature and the surface temperature in response to gaseous particle impingement in a vacuum. The validity of the approach is supported by local, spatially-resolved surface temperature measurements of the thermal response to supersonic microjet gas impingement. The ability to determine and control the adatom effective temperature, and therefore the surface diffusion rate, opens new degrees of freedom in controlling a wide range of nanofabrication processes that critically depend on surface diffusion of precursor molecules. This fundamental understanding has the potential to accelerate research into nanoscale fabrication and to yield the new materials with unique properties that are only accessible with nanoscale features.
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Affiliation(s)
- Matthew R Henry
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
| | - Songkil Kim
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
| | - Andrei G Fedorov
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA. and Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA
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15
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Chilmonczyk MA, Kottke PA, Stevens HY, Guldberg RE, Fedorov AG. Dynamic mass spectrometry probe for electrospray ionization mass spectrometry monitoring of bioreactors for therapeutic cell manufacturing. Biotechnol Bioeng 2019; 116:121-131. [PMID: 30199089 PMCID: PMC6310154 DOI: 10.1002/bit.26832] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 08/29/2018] [Accepted: 09/05/2018] [Indexed: 01/08/2023]
Abstract
Large-scale manufacturing of therapeutic cells requires bioreactor technologies with online feedback control enabled by monitoring of secreted biomolecular critical quality attributes (CQAs). Electrospray ionization mass spectrometry (ESI-MS) is a highly sensitive label-free method to detect and identify biomolecules, but requires extensive sample preparation before analysis, making online application of ESI-MS challenging. We present a microfabricated, monolithically integrated device capable of continuous sample collection, treatment, and direct infusion for ESI-MS detection of biomolecules in high-salt solutions. The dynamic mass spectrometry probe (DMSP) uses a microfluidic mass exchanger to rapidly condition samples for online MS analysis by removing interfering salts, while concurrently introducing MS signal enhancers to the sample for sensitive biomolecular detection. Exploiting this active conditioning capability increases MS signal intensity and signal-to-noise ratio. As a result, sensitivity for low-concentration biomolecules is significantly improved, and multiple proteins can be detected from chemically complex samples. Thus, the DMSP has significant potential to serve as an enabling portion of a novel analytical tool for discovery and monitoring of CQAs relevant to therapeutic cell manufacturing.
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Affiliation(s)
- Mason A. Chilmonczyk
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia
| | - Peter A. Kottke
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia
| | - Hazel Y. Stevens
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia
| | - Robert E. Guldberg
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia
- NSF ERC Center for Therapeutic Cell Manufacturing (CMaT), Parker H. Petit Institute for Bioengineering & Biosciences, Georgia Institute of Technology, Atlanta, Georgia
| | - Andrei G. Fedorov
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia
- NSF ERC Center for Therapeutic Cell Manufacturing (CMaT), Parker H. Petit Institute for Bioengineering & Biosciences, Georgia Institute of Technology, Atlanta, Georgia
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16
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Johnson GE, Prabhakaran V, Browning ND, Mehdi BL, Laskin J, Kottke PA, Fedorov AG. DRILL Interface Makes Ion Soft Landing Broadly Accessible for Energy Science and Applications. Batter Supercaps 2018; 1:97-101. [PMID: 31448364 PMCID: PMC6707734 DOI: 10.1002/batt.201800042] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Indexed: 06/10/2023]
Abstract
Polyoxometalates (POM) have been deposited onto carbon nanotube (CNT) electrodes using benchtop ion soft landing (SL) enabled by a vortex-confined electrohydrodynamic desolvation process. The device is based on the dry ion localization and locomotion (DRILL) mass spectrometry interface of Fedorov and co-workers. By adding electrospray emitters, heating the desolvation gas, and operating at high gas flow rates, it is possible to obtain stable ion currents up to -15 nA that are ideal for deposition. Coupled with ambient ion optics, this interface enables desolvated ions to be delivered to surfaces while excluding solvent and counterions. Electron microscopy of surfaces prepared using the device reveal discrete POM and no aggregation that degrades electrode performance. Characterization of POM-coated CNT electrodes in a supercapacitor showed an energy storage capacity similar to that achieved with SL in vacuum. For solutions that produce primarily a single ion by electrospray ionization, benchtop SL offers a simpler and less costly approach for surface modification with applications in catalysis, energy storage, and beyond.
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Affiliation(s)
- Grant E. Johnson
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352 (USA)
| | | | - Nigel D. Browning
- School of Engineering, Department of Mechanical & Aerospace Engineering, University of Liverpool, Liverpool, L69 3GQ, (UK)
| | - B. Layla Mehdi
- School of Engineering, Department of Mechanical & Aerospace Engineering, University of Liverpool, Liverpool, L69 3GQ, (UK)
| | - Julia Laskin
- Department of Chemistry, Purdue University, West Lafayette, IN 47907 (USA)
| | - Peter A. Kottke
- School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (USA)
| | - Andrei G. Fedorov
- School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (USA)
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17
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Meacham JM, Durvasula K, Degertekin FL, Fedorov AG. Enhanced intracellular delivery via coordinated acoustically driven shear mechanoporation and electrophoretic insertion. Sci Rep 2018; 8:3727. [PMID: 29487375 PMCID: PMC5829135 DOI: 10.1038/s41598-018-22042-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 02/15/2018] [Indexed: 12/13/2022] Open
Abstract
Delivery of large and structurally complex target molecules into cells is vital to the emerging areas of cellular modification and molecular therapy. Inadequacy of prevailing in vivo (viral) and in vitro (liposomal) gene transfer methods for delivery of proteins and a growing diversity of synthetic nanomaterials has encouraged development of alternative physical approaches. Efficacy of injury/diffusion-based delivery via shear mechanoporation is largely insensitive to cell type and target molecule; however, enhanced flexibility is typically accompanied by reduced gene transfer effectiveness. We detail a method to improve transfection efficiency through coordinated mechanical disruption of the cell membrane and electrophoretic insertion of DNA to the cell interior. An array of micromachined nozzles focuses ultrasonic pressure waves, creating a high-shear environment that promotes transient pore formation in membranes of transmitted cells. Acoustic Shear Poration (ASP) allows passive cytoplasmic delivery of small to large nongene macromolecules into established and primary cells at greater than 75% efficiency. Addition of an electrophoretic action enables active transport of target DNA molecules to substantially augment transfection efficiency of passive mechanoporation/diffusive delivery without affecting viability. This two-stage poration/insertion method preserves the compelling flexibility of shear-based delivery, yet substantially enhances capabilities for active transport and transfection of plasmid DNA.
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Affiliation(s)
- J Mark Meacham
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, MO, 63130, USA.
| | | | - F Levent Degertekin
- School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA.,Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, 30332, USA.,G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Andrei G Fedorov
- Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, 30332, USA.,G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
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18
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Kottke PA, Lee JY, Jonke AP, Seneviratne CA, Hecht ES, Muddiman DC, Torres MP, Fedorov AG. DRILL: An Electrospray Ionization-Mass Spectrometry Interface for Improved Sensitivity via Inertial Droplet Sorting and Electrohydrodynamic Focusing in a Swirling Flow. Anal Chem 2017; 89:8981-8987. [PMID: 28612611 DOI: 10.1021/acs.analchem.7b01555] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We describe the DRILL (dry ion localization and locomotion) device, which is an interface for electrospray ionization (ESI)-mass spectrometry (MS) that exploits a swirling flow to enable the use of inertial separation to prescribe different fates for electrosprayed droplets based on their size. This source adds a new approach to charged droplet trajectory manipulation which, when combined with hydrodynamic drag forces and electric field forces, provides a rich range of possible DRILL operational modes. Here, we experimentally demonstrate sensitivity improvement obtained via vortex-induced inertial sorting of electrosprayed droplets/ions: one possible mode of DRILL operation. In this mode, DRILL removes larger droplets while accelerating the remainder of the ESI plume, producing a high velocity stream of gas-enriched spray with small, highly charged droplets and ions and directing it toward the MS inlet. The improved signal-to-noise ratio (10-fold enhancement) in the detection of angiotensin I is demonstrated using the DRILL interface coupled to ESI-MS along with an improved limit of detection (10-fold enhancement, 100 picomole) in the detection of angiotensin II. The utility of DRILL has also been demonstrated by liquid chromatography (LC)-MS: a stable isotope labeled peptide cocktail was spiked into a complex native tissue extract and quantified by unscheduled multiple reaction monitoring on a TSQ Vantage. DRILL demonstrated improved signal strength (up to a 700-fold) for 8 out of 9 peptides and had no effects on the peak shape of the transitions.
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Affiliation(s)
- Peter A Kottke
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Jung Y Lee
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Alex P Jonke
- School of Biological Sciences, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Chinthaka A Seneviratne
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States
| | - Elizabeth S Hecht
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States
| | - David C Muddiman
- Department of Chemistry, North Carolina State University , Raleigh, North Carolina 27695, United States
| | - Matthew P Torres
- School of Biological Sciences, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Andrei G Fedorov
- School of Biological Sciences, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.,Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
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19
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Anderson DM, Yun TM, Kottke PA, Fedorov AG. Comprehensive Analysis of Sorption Enhanced Steam Methane Reforming in a Variable Volume Membrane Reactor. Ind Eng Chem Res 2017. [DOI: 10.1021/acs.iecr.6b04392] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- David M. Anderson
- G. W.
Woodruff School of Mechanical Engineering and ‡Parker H. Petit Institute of Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Thomas M. Yun
- G. W.
Woodruff School of Mechanical Engineering and ‡Parker H. Petit Institute of Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Peter A. Kottke
- G. W.
Woodruff School of Mechanical Engineering and ‡Parker H. Petit Institute of Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Andrei G. Fedorov
- G. W.
Woodruff School of Mechanical Engineering and ‡Parker H. Petit Institute of Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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20
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Abstract
The objective of this paper is to present an engineering model, based on fundamentally sound but simplified treatment of mass diffusion phenomena, for practical predictions of the effective diffusion coefficient of gases through closed-cell foams. All assumptions and simplifications that define the range of applicability of the proposed model are clearly stated. The model developed is based on the electrical circuit analogy and on the first principles. The analysis suggests that the effective diffusion coefficient through the foam can be expressed as a product of the geometric factor and the gas diffusion coefficient through the foam membrane. Comparison of model predictions with experimental data available in the literature shows satisfactory agreement. Discrepancies between predictions and data have been noted for gases with high solubility in the condensed phase for which Henry's law does not apply. Additional experimental data for both the foam morphology and the diffusion coefficient in the membrane are needed to fully validate the model.
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Affiliation(s)
- Laurent Pilon
- Heat Transfer Laboratory, School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907,
| | - Andrei G. Fedorov
- Multiscale Integrated Thermofluidics Laboratory, G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405
| | - Raymond Viskanta
- Heat Transfer Laboratory, School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907
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21
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Kim S, Russell M, Kulkarni DD, Henry M, Kim S, Naik RR, Voevodin AA, Jang SS, Tsukruk VV, Fedorov AG. Activating "Invisible" Glue: Using Electron Beam for Enhancement of Interfacial Properties of Graphene-Metal Contact. ACS Nano 2016; 10:1042-1049. [PMID: 26741645 DOI: 10.1021/acsnano.5b06342] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Interfacial contact of two-dimensional graphene with three-dimensional metal electrodes is crucial to engineering high-performance graphene-based nanodevices with superior performance. Here, we report on the development of a rapid "nanowelding" method for enhancing properties of interface to graphene buried under metal electrodes using a focused electron beam induced deposition (FEBID). High energy electron irradiation activates two-dimensional graphene structure by generation of structural defects at the interface to metal contacts with subsequent strong bonding via FEBID of an atomically thin graphitic interlayer formed by low energy secondary electron-assisted dissociation of entrapped hydrocarbon contaminants. Comprehensive investigation is conducted to demonstrate formation of the FEBID graphitic interlayer and its impact on contact properties of graphene devices achieved via strong electromechanical coupling at graphene-metal interfaces. Reduction of the device electrical resistance by ∼50% at a Dirac point and by ∼30% at the gate voltage far from the Dirac point is obtained with concurrent improvement in thermomechanical reliability of the contact interface. Importantly, the process is rapid and has an excellent insertion potential into a conventional fabrication workflow of graphene-based nanodevices through single-step postprocessing modification of interfacial properties at the buried heterogeneous contact.
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Affiliation(s)
| | | | | | | | - Steve Kim
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson AFB, Ohio 45433-7707, United States
| | - Rajesh R Naik
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson AFB, Ohio 45433-7707, United States
| | - Andrey A Voevodin
- Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright Patterson AFB, Ohio 45433-7707, United States
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22
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Fisher JS, Kottke PA, Kim S, Fedorov AG. Rapid Electron Beam Writing of Topologically Complex 3D Nanostructures Using Liquid Phase Precursor. Nano Lett 2015; 15:8385-91. [PMID: 26561872 DOI: 10.1021/acs.nanolett.5b04225] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Advancement of focused electron beam-induced deposition (FEBID) as a versatile direct-write additive nanoscale fabrication technique has been inhibited by poor throughput, limited choice of precursors, and restrictions on possible 3D topologies. Here, we demonstrate FEBID using nanoelectrospray liquid precursor injection to grow carbon and pure metal nanostructures via direct decomposition and electrochemical reduction of the relevant precursors, achieving growth rates 10(5) times greater than those observed in standard gas-phase FEBID. Initiating growth at the free surface of a liquid pool enables fabrication of complex 3D carbon nanostructures with strong adhesion to the substrate. Deposition of silver microstructures at similar growth rates is also demonstrated as a promising avenue for future development of the technique.
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Affiliation(s)
- Jeffrey S Fisher
- George W. Woodruff School of Mechanical Engineering and ‡Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Peter A Kottke
- George W. Woodruff School of Mechanical Engineering and ‡Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Songkil Kim
- George W. Woodruff School of Mechanical Engineering and ‡Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Andrei G Fedorov
- George W. Woodruff School of Mechanical Engineering and ‡Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
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23
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Kim S, Russell M, Henry M, Kim SS, Naik RR, Voevodin AA, Jang SS, Tsukruk VV, Fedorov AG. Dynamic modulation of electronic properties of graphene by localized carbon doping using focused electron beam induced deposition. Nanoscale 2015; 7:14946-14952. [PMID: 26302897 DOI: 10.1039/c5nr04063a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report on the first demonstration of controllable carbon doping of graphene to engineer local electronic properties of a graphene conduction channel using focused electron beam induced deposition (FEBID). Electrical measurements indicate that an "n-p-n" junction on graphene conduction channel is formed by partial carbon deposition near the source and drain metal contacts by low energy (<50 eV) secondary electrons due to inelastic collisions of long range backscattered primary electrons generated from a low dose of high energy (25 keV) electron beam (1 × 10(18) e(-) per cm(2)). Detailed AFM imaging provides direct evidence of the new mechanism responsible for dynamic evolution of the locally varying graphene doping. The FEBID carbon atoms, which are physisorbed and weakly bound to graphene, diffuse towards the middle of graphene conduction channel due to their surface chemical potential gradient, resulting in negative shift of Dirac voltage. Increasing a primary electron dose to 1 × 10(19) e(-) per cm(2) results in a significant increase of carbon deposition, such that it covers the entire graphene conduction channel at high surface density, leading to n-doping of graphene channel. Collectively, these findings establish a unique capability of FEBID technique to dynamically modulate the doping state of graphene, thus enabling a new route to resist-free, "direct-write" functional patterning of graphene-based electronic devices with potential for on-demand re-configurability.
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Affiliation(s)
- S Kim
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.
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24
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Anderson DM, Nasr MH, Yun TM, Kottke PA, Fedorov AG. Sorption-Enhanced Variable-Volume Batch–Membrane Steam Methane Reforming at Low Temperature: Experimental Demonstration and Kinetic Modeling. Ind Eng Chem Res 2015. [DOI: 10.1021/acs.iecr.5b01879] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- David M. Anderson
- G.W. Woodruff School of Mechanical Engineering and ‡Parker H. Petit
Institute of Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta Georgia 30332, United States
| | - Mohamed H. Nasr
- G.W. Woodruff School of Mechanical Engineering and ‡Parker H. Petit
Institute of Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta Georgia 30332, United States
| | - Thomas M. Yun
- G.W. Woodruff School of Mechanical Engineering and ‡Parker H. Petit
Institute of Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta Georgia 30332, United States
| | - Peter A. Kottke
- G.W. Woodruff School of Mechanical Engineering and ‡Parker H. Petit
Institute of Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta Georgia 30332, United States
| | - Andrei G. Fedorov
- G.W. Woodruff School of Mechanical Engineering and ‡Parker H. Petit
Institute of Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta Georgia 30332, United States
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25
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Silva JE, Geryak R, Loney DA, Kottke PA, Naik RR, Tsukruk VV, Fedorov AG. Stick-slip water penetration into capillaries coated with swelling hydrogel. Soft Matter 2015; 11:5933-5939. [PMID: 26119374 DOI: 10.1039/c5sm00660k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We have observed intriguing stick-slip behavior during capillary pressure driven filling of borosilicate microtubes coated with hydrogel on their inner wall. Swelling of hydrogel upon exposure to a translating waterfront is accompanied by "stick-and-slip" motion. This results in the macroscopic filling velocity for water penetration into glass capillaries coated with poly(N-isopropylacrylamide) (PNIPAM) being constant throughout the filling process, and reduced by three orders of magnitude when compared to filling of uncoated capillaries. A simple scaling analysis is used to introduce a possible explanation by considering the mechanisms responsible for pinning and unpinning of the contact line. The explanation assumes that the time scale for water diffusion into a hydrogel film and the resulting swelling/change of the local meniscus contact angle define the duration of each "stick" event. The "slip" length scale is in turn established by the elastocapillary deformation of dry hydrogel at the pinning point of the contact line. The sequential dynamics of these processes then determine the rate of water filling into a swelling capillary. Collectively, these experimental and theoretical results provide a new conceptual framework for liquid motion confined by soft, dynamically evolving polymer interfaces, in which the system creates an energy barrier to further motion through elasto-capillary deformation, and then lowers the barrier through diffusive softening. This insight has implications for optimal design of microfluidic and lab-on-a-chip devices based on stimuli-responsive smart polymers.
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Affiliation(s)
- J E Silva
- Department of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
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26
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Tibavinsky IA, Kottke PA, Fedorov AG. Microfabricated ultrarapid desalting device for nanoelectrospray ionization mass spectrometry. Anal Chem 2015; 87:351-6. [PMID: 25490085 PMCID: PMC4287832 DOI: 10.1021/ac5040083] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 12/09/2014] [Indexed: 01/26/2023]
Abstract
Salt removal is a prerequisite for electrospray ionization mass spectrometry (ESI-MS) analysis of biological samples. Rapid desalting and a low volume connection to an electrospray tip are required for time-resolved measurements. We have developed a microfabricated desalting device that meets both requirements, thus providing the foundational technology piece for transient ESI-MS measurements of complex biological liquid specimens. In the microfabricated device, the sample flows in a channel separated from a higher flow rate, salt-free counter solution by a monolithically integrated nanoporous alumina membrane, which can support pressure differences between the flow channels of over 600 kPa. Salt is removed by exploiting the large difference in diffusivities between salts and the typical ESI-MS target bioanalytes, e.g., peptides and proteins. We demonstrate the capability to remove 95% of salt from a sample solution in ∼1 s while retaining sufficiently high concentration of a relatively low molecular weight protein, cytochrome-c, for ESI-MS detection.
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Affiliation(s)
- Ivan A. Tibavinsky
- George
W. Woodruff School of Mechanical Engineering and Parker H. Petit Institute for Bioengineering
& Biosciences, Georgia Institute of
Technology, Atlanta, Georgia 30332, United
States
| | - Peter A. Kottke
- George
W. Woodruff School of Mechanical Engineering and Parker H. Petit Institute for Bioengineering
& Biosciences, Georgia Institute of
Technology, Atlanta, Georgia 30332, United
States
| | - Andrei G. Fedorov
- George
W. Woodruff School of Mechanical Engineering and Parker H. Petit Institute for Bioengineering
& Biosciences, Georgia Institute of
Technology, Atlanta, Georgia 30332, United
States
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Davydova SV, Fedorov AG, Klimov AE, Gaboyan AS. [STENTING VERSUS PALLIATIVE SURGERY IN PATIENTS WITH MALIGNANT GASTROINTESTINAL STENOSIS]. Eksp Klin Gastroenterol 2015:71-76. [PMID: 26415269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
AIM Retrospective analysis of the results of stenting versus surgical palliation in patients with malignant gastrointestinal stenosis. MATERIAL AND METHODS 85 patients underwent endoscopic stenting (41) or surgical intervention (44). Level of stenosis: gastric outlet (23/38), multi-level gastric obstruction (2/3), duodenum or jejunum (12/3), gastrojejunoanastomosis (3/0) and gastroduodenoanastomosis (1/0). 49 self-expanding metal stents were implanted in 41 patients. 41 gastroenteroanastomoses and 3 jejunostomas were performed in surgical group. RESULTS Stents were successfully inserted in all patients. Early complications were observed in 3 (7.3%) patients after stenting and in 9 (20.5%) after surgical palliation, p = 0.0755. Postoperative lethality was 2,4% (1 patient) after stenting and 31.8% (14 patients) after surgery, p = 0.0003. Mean hospital stay was 15 days in stenting group and 23 days in surgical group, p < 0.001. There was no statistically significant difference in long-term results, neither in late complications (p = 0.3691), nor in survival (p =0.3697). CONCLUSION Endoscopic placement of self-expanding stents is an effective method of restoration of oral intake in patients with malignant gastrointestinal obstruction. Stenting is associated with equal rates of early and late complications, lower mortality and decreased in-hospital stay as compared with surgery, and therefore may be recommended as a final palliation in inoperable patients.
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28
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Yun TM, Kottke PA, Anderson DM, Fedorov AG. Power Density Assessment of Variable Volume Batch Reactors for Hydrogen Production with Dynamically Modulated Liquid Fuel Introduction. Ind Eng Chem Res 2014. [DOI: 10.1021/ie500990d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Thomas M. Yun
- George W. Woodruff School of Mechanical Engineering and ‡Parker H. Petit
Institute of Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, United States
| | - Peter A. Kottke
- George W. Woodruff School of Mechanical Engineering and ‡Parker H. Petit
Institute of Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, United States
| | - David M. Anderson
- George W. Woodruff School of Mechanical Engineering and ‡Parker H. Petit
Institute of Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, United States
| | - Andrei G. Fedorov
- George W. Woodruff School of Mechanical Engineering and ‡Parker H. Petit
Institute of Bioengineering
and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, United States
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29
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Kim S, Kulkarni DD, Davis R, Kim SS, Naik RR, Voevodin AA, Russell M, Jang SS, Tsukruk VV, Fedorov AG. Controlling the physicochemical state of carbon on graphene using focused electron-beam-induced deposition. ACS Nano 2014; 8:6805-6813. [PMID: 24988046 DOI: 10.1021/nn5011073] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Focused electron-beam-induced deposition (FEBID) is a promising nanolithography technique using "direct-write" patterning by carbon line and dot deposits on graphene. Understanding interactions between deposited carbon molecules and graphene enables highly localized modification of graphene properties, which is foundational to the FEBID utility as a nanopatterning tool. In this study, we demonstrate a unique possibility to induce dramatically different adsorption states of FEBID-produced carbon deposits on graphene, through density functional theory calculations and complementary Raman experiments. Specifically, an amorphous carbon deposit formed by direct irradiation of high energy primary electrons exhibits unusually strong interactions with graphene via covalent bonding, whereas the FEBID carbon formed due to low-energy secondary electrons is only weakly interacting with graphene via physisorption. These observations not only are of fundamental importance to basic physical chemistry of FEBID carbon-graphene interactions but also enable the use of selective laser-assisted postdeposition ablation to effectively remove the parasitically deposited, physisorbed carbon films for improving FEBID patterning resolution.
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Affiliation(s)
- Songkil Kim
- George W. Woodruff School of Mechanical Engineering, ‡School of Materials Science and Engineering, and §Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
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30
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Kulkarni DD, Kim S, Chyasnavichyus M, Hu K, Fedorov AG, Tsukruk VV. Chemical Reduction of Individual Graphene Oxide Sheets as Revealed by Electrostatic Force Microscopy. J Am Chem Soc 2014; 136:6546-9. [DOI: 10.1021/ja5005416] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dhaval D. Kulkarni
- School
of Materials Science and Engineering and ‡George W. Woodruff School of Mechanical
Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Songkil Kim
- School
of Materials Science and Engineering and ‡George W. Woodruff School of Mechanical
Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Marius Chyasnavichyus
- School
of Materials Science and Engineering and ‡George W. Woodruff School of Mechanical
Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Kesong Hu
- School
of Materials Science and Engineering and ‡George W. Woodruff School of Mechanical
Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Andrei G. Fedorov
- School
of Materials Science and Engineering and ‡George W. Woodruff School of Mechanical
Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Vladimir V. Tsukruk
- School
of Materials Science and Engineering and ‡George W. Woodruff School of Mechanical
Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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31
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Zhou W, Loney D, Fedorov AG, Degertekin FL, Rosen DW. Lattice Boltzmann simulations of multiple-droplet interaction dynamics. Phys Rev E Stat Nonlin Soft Matter Phys 2014; 89:033311. [PMID: 24730971 DOI: 10.1103/physreve.89.033311] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Indexed: 06/03/2023]
Abstract
A lattice Boltzmann (LB) formulation, which is consistent with the phase-field model for two-phase incompressible fluid, is proposed to model the interface dynamics of droplet impingement. The interparticle force is derived by comparing the macroscopic transport equations recovered from LB equations with the governing equations of the continuous phase-field model. The inconsistency between the existing LB implementations and the phase-field model in calculating the relaxation time at the phase interface is identified and an approximation is proposed to ensure the consistency with the phase-field model. It is also shown that the commonly used equilibrium velocity boundary for the binary fluid LB scheme does not conserve momentum at the wall boundary and a modified scheme is developed to ensure the momentum conservation at the boundary. In addition, a geometric formulation of the wetting boundary condition is proposed to replace the popular surface energy formulation and results show that the geometric approach enforces the prescribed contact angle better than the surface energy formulation in both static and dynamic wetting. The proposed LB formulation is applied to simulating droplet impingement dynamics in three dimensions and results are compared to those obtained with the continuous phase-field model, the LB simulations reported in the literature, and experimental data from the literature. The results show that the proposed LB simulation approach yields not only a significant speed improvement over the phase-field model in simulating droplet impingement dynamics on a submillimeter length scale, but also better accuracy than both the phase-field model and the previously reported LB techniques when compared to experimental data. Upon validation, the proposed LB modeling methodology is applied to the study of multiple-droplet impingement and interactions in three dimensions, which demonstrates its powerful capability of simulating extremely complex interface phenomena.
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Affiliation(s)
- Wenchao Zhou
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, USA
| | - Drew Loney
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, USA
| | - Andrei G Fedorov
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, USA and Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, USA
| | - F Levent Degertekin
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, USA and Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, USA
| | - David W Rosen
- The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, USA
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32
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Meacham JM, Durvasula K, Degertekin FL, Fedorov AG. Physical methods for intracellular delivery: practical aspects from laboratory use to industrial-scale processing. ACTA ACUST UNITED AC 2013; 19:1-18. [PMID: 23813915 DOI: 10.1177/2211068213494388] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Effective intracellular delivery is a significant impediment to research and therapeutic applications at all processing scales. Physical delivery methods have long demonstrated the ability to deliver cargo molecules directly to the cytoplasm or nucleus, and the mechanisms underlying the most common approaches (microinjection, electroporation, and sonoporation) have been extensively investigated. In this review, we discuss established approaches, as well as emerging techniques (magnetofection, optoinjection, and combined modalities). In addition to operating principles and implementation strategies, we address applicability and limitations of various in vitro, ex vivo, and in vivo platforms. Importantly, we perform critical assessments regarding (1) treatment efficacy with diverse cell types and delivered cargo molecules, (2) suitability to different processing scales (from single cell to large populations), (3) suitability for automation/integration with existing workflows, and (4) multiplexing potential and flexibility/adaptability to enable rapid changeover between treatments of varied cell types. Existing techniques typically fall short in one or more of these criteria; however, introduction of micro-/nanotechnology concepts, as well as synergistic coupling of complementary method(s), can improve performance and applicability of a particular approach, overcoming barriers to practical implementation. For this reason, we emphasize these strategies in examining recent advances in development of delivery systems.
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33
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Gittens RA, Olivares-Navarrete R, Cheng A, Anderson DM, McLachlan T, Stephan I, Geis-Gerstorfer J, Sandhage KH, Fedorov AG, Rupp F, Boyan BD, Tannenbaum R, Schwartz Z. The roles of titanium surface micro/nanotopography and wettability on the differential response of human osteoblast lineage cells. Acta Biomater 2013; 9:6268-77. [PMID: 23232211 DOI: 10.1016/j.actbio.2012.12.002] [Citation(s) in RCA: 177] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 11/28/2012] [Accepted: 12/02/2012] [Indexed: 12/26/2022]
Abstract
Surface micro- and nanostructural modifications of dental and orthopedic implants have shown promising in vitro, in vivo and clinical results. Surface wettability has also been suggested to play an important role in osteoblast differentiation and osseointegration. However, the available techniques to measure surface wettability are not reliable on clinically relevant, rough surfaces. Furthermore, how the differentiation state of osteoblast lineage cells impacts their response to micro/nanostructured surfaces, and the role of wettability on this response, remain unclear. In the current study, surface wettability analyses (optical sessile drop analysis, environmental scanning electron microscopic analysis and the Wilhelmy technique) indicated hydrophobic static responses for deposited water droplets on microrough and micro/nanostructured specimens, while hydrophilic responses were observed with dynamic analyses of micro/nanostructured specimens. The maturation and local factor production of human immature osteoblast-like MG63 cells was synergistically influenced by nanostructures superimposed onto microrough titanium (Ti) surfaces. In contrast, human mesenchymal stem cells cultured on micro/nanostructured surfaces in the absence of exogenous soluble factors exhibited less robust osteoblastic differentiation and local factor production compared to cultures on unmodified microroughened Ti. Our results support previous observations using Ti6Al4V surfaces showing that recognition of surface nanostructures and subsequent cell response is dependent on the differentiation state of osteoblast lineage cells. The results also indicate that this effect may be partly modulated by surface wettability. These findings support the conclusion that the successful osseointegration of an implant depends on contributions from osteoblast lineage cells at different stages of osteoblast commitment.
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Affiliation(s)
- Rolando A Gittens
- School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0363, USA
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34
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Hildreth OJ, Rykaczewski K, Fedorov AG, Wong CP. A DLVO model for catalyst motion in metal-assisted chemical etching based upon controlled out-of-plane rotational etching and force-displacement measurements. Nanoscale 2013; 5:961-970. [PMID: 23238167 DOI: 10.1039/c2nr32293e] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Metal-assisted Chemical Etching of silicon has recently emerged as a powerful technique to fabricate 1D, 2D, and 3D nanostructures in silicon with high feature fidelity. This work demonstrates that out-of-plane rotational catalysts utilizing polymer pinning structures can be designed with excellent control over rotation angle. A plastic deformation model was developed establishing that the catalyst is driven into the silicon substrate with a minimum pressure differential across the catalyst thickness of 0.4-0.6 MPa. Force-displacement curves were gathered between an Au tip and Si or SiO(2) substrates under acidic conditions to show that Derjaguin and Landau, Verwey and Overbeek (DLVO) based forces are capable of providing restorative forces on the order of 0.2-0.3 nN with a calculated 11-18 MPa pressure differential across the catalyst. This work illustrates that out-of-plane rotational structures can be designed with controllable rotation and also suggests a new model for the driving force for catalyst motion based on DLVO theory. This process enables the facile fabrication of vertically aligned thin-film metallic structures and scalloped nanostructures in silicon for applications in 3D micro/nano-electromechanical systems, photonic devices, nanofluidics, etc.
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Affiliation(s)
- Owen J Hildreth
- School of Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, USA.
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35
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Fedorov AG, Davydova SV, Klimov AE, Lebedev NV. [Results of the upper digestive tract stenting with self-expanding stents]. Khirurgiia (Mosk) 2013:34-38. [PMID: 24077504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The work is based on the analysis of the palliative treatment of 66 patients with malignant upper digestive tract obstruction who underwent implantation of 75 self-expanding metallic stents in the period of 2003-2012 yy. Early postoperative complications developed in 10 (15.2%) cases. Procedure-related complications were observed in 8 (12.1%) patients, non-specific complications occurred in 2 (3.0%) patients. In-hospital lethality was 4.5% (3 patients). 51 patients were followed until death. Symptomatic relapse of obstruction was observed in 4 cases. Median survival was 97 days. Stenting with self-expanding metal stents was concluded to be an effective and safe method of palliation of malignant upper digestive tract stenosis.
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36
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Hildreth OJ, Fedorov AG, Wong CP. 3D spirals with controlled chirality fabricated using metal-assisted chemical etching of silicon. ACS Nano 2012; 6:10004-12. [PMID: 23039816 DOI: 10.1021/nn303680k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The ability to fabricate 3D spiraling structures using metal-assisted chemical etching (MaCE) is one of the unique advantages of MaCE over traditional etching methods. However, control over the chirality of the spiraling structures has not been established. In this work, a systematic parametric study was undertaken for MaCE of star-shaped catalysts, examining the influence of arm shape, arm length, number of arms, center core diameter, and catalyst thickness on the rotation direction. This data was used to identify a set of geometric parameters that reliably induce rotation in a predefined direction such that large arrays of 3D spiraling structures can be fabricated with the same chirality. Electroless deposition into the MaCE template was used to examine the full etch path of the catalyst and an experimental fit was established to control rotation angle by adjusting the catalyst's center core diameter. The ability to fabricate large arrays of 3D spiraling structures with predefined chirality could have important applications in photonics and optoelectronics.
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Affiliation(s)
- Owen J Hildreth
- School of Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, United States.
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37
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Wei W, Fedorov AG, Luo Z, Ni M. Radiative properties of dense nanofluids. Appl Opt 2012; 51:6159-6171. [PMID: 22945164 DOI: 10.1364/ao.51.006159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Accepted: 07/29/2012] [Indexed: 06/01/2023]
Abstract
The radiative properties of dense nanofluids are investigated. For nanofluids, scattering and absorbing of electromagnetic waves by nanoparticles, as well as light absorption by the matrix/fluid in which the nanoparticles are suspended, should be considered. We compare five models for predicting apparent radiative properties of nanoparticulate media and evaluate their applicability. Using spectral absorption and scattering coefficients predicted by different models, we compute the apparent transmittance of a nanofluid layer, including multiple reflecting interfaces bounding the layer, and compare the model predictions with experimental results from the literature. Finally, we propose a new method to calculate the spectral radiative properties of dense nanofluids that shows quantitatively good agreement with the experimental results.
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Affiliation(s)
- Wei Wei
- State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou, Zhejiang 310027, China
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38
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Anderson DM, Gupta MK, Voevodin AA, Hunter CN, Putnam SA, Tsukruk VV, Fedorov AG. Using amphiphilic nanostructures to enable long-range ensemble coalescence and surface rejuvenation in dropwise condensation. ACS Nano 2012; 6:3262-3268. [PMID: 22456273 DOI: 10.1021/nn300183d] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Controlling coalescence events in a heterogeneous ensemble of condensing droplets on a surface is an outstanding fundamental challenge in surface and interfacial sciences, with a broad practical importance in applications ranging from thermal management of high-performance electronic devices to moisture management in high-humidity environments. Nature-inspired superhydrophobic surfaces have been actively explored to enhance heat and mass transfer rates by achieving favorable dynamics during dropwise condensation; however, the effectiveness of such chemically homogeneous surfaces has been limited because condensing droplets tend to form as pinned Wenzel drops rather than mobile Cassie ones. Here, we introduce an amphiphilic nanostructured surface, consisting of a hydrophilic base with hydrophobic tips, which promotes the periodic regeneration of nucleation sites for small droplets, thus rendering the surface self-rejuvenating. This unique amphiphilic nanointerface generates an arrangement of condensed Wenzel droplets that are fluidically linked by a wetted sublayer, promoting previously unobserved coalescence events where numerous droplets simultaneously merge, without direct contact. Such ensemble coalescences rapidly create fresh nucleation sites, thereby shifting the overall population toward smaller droplets and enhancing the rates of mass and heat transfer during condensation.
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Affiliation(s)
- David M Anderson
- G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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39
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Abstract
A semianalytical, continuum analysis of evaporation of water confined in a cylindrical nanopore is presented, wherein the combined effect of electrostatic interaction and van der Waals forces is taken into account. The equations governing fluid flow and heat transfer between liquid and vapor phases are partially integrated analytically, to yield a set of ordinary differential equations, which are solved numerically to determine the flow characteristics and effect on the resulting shape and rate of evaporation from the liquid-vapor interface. The analysis identifies three important parameters that significantly affect the overall performance of the system, namely, the capillary radius, pore-wall temperature, and the degree of saturation of vapor phase. The extension of meniscus is found to be prominent for smaller nanoscale capillaries, in turn yielding a greater net rate of evaporation per unit pore area. The effects of temperature and ambient vapor pressure on net rate of evaporation are shown to be analogous. An increase in pore-wall temperature, which enhances saturation pressure, or a decrease in the ambient vapor pressure result in enhancing the net potential for evaporation and increasing the curvature of the interface.
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Affiliation(s)
- Shankar Narayanan
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
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40
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Varady MJ, Fedorov AG. Fuel Reformation and Hydrogen Generation with Direct Droplet Impingement Reactors: Parametric Study and Design Considerations for Portable Methanol Steam Reformers. Ind Eng Chem Res 2011. [DOI: 10.1021/ie200564x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Mark J. Varady
- Multiscale Integrated Thermofluidics Research Laboratory, GWW School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, United States
| | - Andrei G. Fedorov
- Multiscale Integrated Thermofluidics Research Laboratory, GWW School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, United States
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41
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Varady MJ, Fedorov AG. Fuel Reformation and Hydrogen Generation with Direct Droplet Impingement Reactors: Model Formulation and Validation. Ind Eng Chem Res 2011. [DOI: 10.1021/ie200563e] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mark J. Varady
- Multiscale Integrated Thermofluidics Research Laboratory, GWW School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, United States
| | - Andrei G. Fedorov
- Multiscale Integrated Thermofluidics Research Laboratory, GWW School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405, United States
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42
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Rykaczewski K, Hildreth OJ, Wong CP, Fedorov AG, Scott JHJ. Guided three-dimensional catalyst folding during metal-assisted chemical etching of silicon. Nano Lett 2011; 11:2369-2374. [PMID: 21526791 DOI: 10.1021/nl200715m] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In recent years metal-assisted chemical etching (MaCE) of silicon, in which etching is confined to a small region surrounding metal catalyst templates, has emerged as a promising low cost alternative to commonly used three-dimensional (3D) fabrication techniques. We report a new methodology for controllable folding of 2D metal catalyst films into 3D structures using MaCE. This method takes advantage of selective patterning of the catalyst layer into regions with mismatched characteristic dimensions, resulting in uneven etching rates along the notched boundary lines that produce hinged 2D templates for 3D folding. We explore the dynamics of the folding process of the hinged templates, demonstrating that the folding action combines rotational and translational motion of the catalyst template, which yields topologically complex 3D nanostructures with intimately integrated metal and silicon features.
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Affiliation(s)
- Konrad Rykaczewski
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8370, United States.
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43
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Kulkarni DD, Rykaczewski K, Singamaneni S, Kim S, Fedorov AG, Tsukruk VV. Thermally induced transformations of amorphous carbon nanostructures fabricated by electron beam induced deposition. ACS Appl Mater Interfaces 2011; 3:710-720. [PMID: 21319745 DOI: 10.1021/am1010173] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
We studied the thermally induced phase transformations of electron-beam-induced deposited (EBID) amorphous carbon nanostructures by correlating the changes in its morphology with internal microstructure by using combined atomic force microscopy (AFM) and high resolution confocal Raman microscopy. These carbon deposits can be used to create heterogeneous junctions in electronic devices commonly known as carbon-metal interconnects. We compared two basic shapes of EBID deposits: dots/pillars with widths from 50 to 600 nm and heights from 50 to 500 nm and lines with variable heights from 10 to 150 nm but having a constant length of 6 μm. We observed that during thermal annealing, the nanoscale amorphous deposits go through multistage transformation including dehydration and stress-relaxation around 150 °C, dehydrogenation within 150-300 °C, followed by graphitization (>350 °C) and formation of nanocrystalline, highly densified graphitic deposits around 450 °C. The later stage of transformation occurs well below commonly observed graphitization for bulk carbon (600-800 °C). It was observed that the shape of the deposits contribute significantly to the phase transformations. We suggested that this difference is controlled by different contributions from interfacial footprints area. Moreover, the rate of graphitization was different for deposits of different shapes with the lines showing a much stronger dependence of its structure on the density than the dots.
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Affiliation(s)
- Dhaval D Kulkarni
- School of Material Science and Engineering and Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, United States
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44
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Rykaczewski K, Hildreth OJ, Wong CP, Fedorov AG, Scott JHJ. Directed 2D-to-3D pattern transfer method for controlled fabrication of topologically complex 3D features in silicon. Adv Mater 2011; 23:659-663. [PMID: 21274916 DOI: 10.1002/adma.201003833] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Indexed: 05/30/2023]
Abstract
A process that allows control over the 3D motion of catalyst nanostructures during metal-assisted chemical etching by their local pinning prior to etching is demonstrated. The pinning material acts as a fulcrum for rotation of the catalyst structures resulting in etching of silicon features with rotational geometry.
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Affiliation(s)
- Konrad Rykaczewski
- Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899-8370, USA.
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45
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Forbes TP, Degertekin FL, Fedorov AG. Droplet charging regimes for ultrasonic atomization of a liquid electrolyte in an external electric field. Phys Fluids (1994) 2011; 23:12104. [PMID: 21301636 PMCID: PMC3033869 DOI: 10.1063/1.3541818] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Accepted: 12/21/2010] [Indexed: 05/30/2023]
Abstract
Distinct regimes of droplet charging, determined by the dominant charge transport process, are identified for an ultrasonic droplet ejector using electrohydrodynamic computational simulations, a fundamental scale analysis, and experimental measurements. The regimes of droplet charging are determined by the relative magnitudes of the dimensionless Strouhal and electric Reynolds numbers, which are a function of the process (pressure forcing), advection, and charge relaxation time scales for charge transport. Optimal (net maximum) droplet charging has been identified to exist for conditions in which the electric Reynolds number is of the order of the inverse Strouhal number, i.e., the charge relaxation time is on the order of the pressure forcing (droplet formation) time scale. The conditions necessary for optimal droplet charging have been identified as a function of the dimensionless Debye number (i.e., liquid conductivity), external electric field (magnitude and duration), and atomization drive signal (frequency and amplitude). The specific regime of droplet charging also determines the functional relationship between droplet charge and charging electric field strength. The commonly expected linear relationship between droplet charge and external electric field strength is only found when either the inverse of the Strouhal number is less than the electric Reynolds number, i.e., the charge relaxation is slower than both the advection and external pressure forcing, or in the electrostatic limit, i.e., when charge relaxation is much faster than all other processes. The analysis provides a basic understanding of the dominant physics of droplet charging with implications to many important applications, such as electrospray mass spectrometry, ink jet printing, and drop-on-demand manufacturing.
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Forbes TP, Degertekin FL, Fedorov AG. Regime transition in electromechanical fluid atomization and implications to analyte ionization for mass spectrometric analysis. J Am Soc Mass Spectrom 2010; 21:1900-1905. [PMID: 20729096 PMCID: PMC4451205 DOI: 10.1016/j.jasms.2010.07.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Revised: 07/19/2010] [Accepted: 07/22/2010] [Indexed: 05/29/2023]
Abstract
The physical processes governing the transition from purely mechanical ejection to electromechanical ejection to electrospraying are investigated through complementary scaling analysis and optical visualization. Experimental characterization and visualization are performed with the ultrasonically-driven array of micromachined ultrasonic electrospray (AMUSE) ion source to decouple the electrical and mechanical fields. A new dimensionless parameter, the Fenn number, is introduced to define a transition between the spray regimes, in terms of its dependence on the characteristic Strouhal number for the ejection process. A fundamental relationship between the Fenn and Strouhal numbers is theoretically derived and confirmed experimentally in spraying liquid electrolytes of different ionic strength subjected to a varying magnitude electric field. This relationship and the basic understanding of the charged droplet generation physics have direct implications on the optimal ionization efficiency and mass spectrometric response for different types of analytes.
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Affiliation(s)
- Thomas P Forbes
- G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
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Forbes TP, Degertekin FL, Fedorov AG. Electrochemical Ionization and Analyte Charging in the Array of Micromachined UltraSonic Electrospray (AMUSE) Ion Source. J Electroanal Chem (Lausanne) 2010; 645:167-173. [PMID: 20607111 DOI: 10.1016/j.jelechem.2010.05.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Electrochemistry and ion transport in a planar array of mechanically-driven, droplet-based ion sources are investigated using an approximate time scale analysis and in-depth computational simulations. The ion source is modeled as a controlled-current electrolytic cell, in which the piezoelectric transducer electrode, which mechanically drives the charged droplet generation using ultrasonic atomization, also acts as the oxidizing/corroding anode (positive mode). The interplay between advective and diffusive ion transport of electrochemically generated ions is analyzed as a function of the transducer duty cycle and electrode location. A time scale analysis of the relative importance of advective vs. diffusive ion transport provides valuable insight into optimality, from the ionization prospective, of alternative design and operation modes of the ion source operation. A computational model based on the solution of time-averaged, quasi-steady advection-diffusion equations for electroactive species transport is used to substantiate the conclusions of the time scale analysis. The results show that electrochemical ion generation at the piezoelectric transducer electrodes located at the back-side of the ion source reservoir results in poor ionization efficiency due to insufficient time for the charged analyte to diffuse away from the electrode surface to the ejection location, especially at near 100% duty cycle operation. Reducing the duty cycle of droplet/analyte ejection increases the analyte residence time and, in turn, improves ionization efficiency, but at an expense of the reduced device throughput. For applications where this is undesirable, i.e., multiplexed and disposable device configurations, an alternative electrode location is incorporated. By moving the charging electrode to the nozzle surface, the diffusion length scale is greatly reduced, drastically improving ionization efficiency. The ionization efficiency of all operating conditions considered is expressed as a function of the dimensionless Peclet number, which defines the relative effect of advection as compared to diffusion. This analysis is general enough to elucidate an important role of electrochemistry in ionization efficiency of any arrayed ion sources, be they mechanically-driven or electrosprays, and is vital for determining optimal design and operation conditions.
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Affiliation(s)
- Thomas P Forbes
- G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
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Rykaczewski K, Hildreth OJ, Kulkarni D, Henry MR, Kim SK, Wong CP, Tsukruk VV, Fedorov AG. Maskless and resist-free rapid prototyping of three-dimensional structures through electron beam induced deposition (EBID) of carbon in combination with metal-assisted chemical etching (MaCE) of silicon. ACS Appl Mater Interfaces 2010; 2:969-973. [PMID: 20356053 DOI: 10.1021/am1000773] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
In this work, we introduce a maskless, resist-free rapid prototyping method to fabricate three-dimensional structures using electron beam induced deposition (EBID) of amorphous carbon (aC) from a residual hydrocarbon precursor in combination with metal-assisted chemical etching (MaCE) of silicon. We demonstrate that EBID-made patterned aC coating, with thickness of even a few nanometers, acts as a negative "mask" for the etching process and is sufficient for localized termination of the MaCE of silicon. Optimal aC deposition settings and gold film thickness for fabrication of high-aspect-ratio nanoscale 3D silicon structures are determined. The speed necessary for optimal aC feature deposition is found to be comparable to the writing speed of standard Electron Beam Lithography and the MaCE etching rate is found to be comparable to standard deep reactive ion etching (DRIE) rate.
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Forbes TP, Degertekin FL, Fedorov AG. Electrohydrodynamics of charge separation in droplet-based ion sources with time-varying electrical and mechanical actuation. J Am Soc Mass Spectrom 2010; 21:501-510. [PMID: 20149681 PMCID: PMC2847640 DOI: 10.1016/j.jasms.2009.12.022] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 12/28/2009] [Accepted: 12/31/2009] [Indexed: 05/27/2023]
Abstract
Charge transport and separation in mechanically-driven, droplet-based ion sources are investigated using computational analysis and supporting experiments. A first-principles model of electrohydrodynamics (EHD) and charge migration is formulated and implemented using FLUENT CFD software for jet/droplet formation. For validation, classical experiments of electrospraying from a thin capillary are simulated, specifically, the transient EHD cone-jet formation of a fluid with finite electrical conductivity, and the Taylor cone formation in a perfectly electrically-conducting fluid. The model is also used to investigate the microscopic physics of droplet charging in mechanically-driven droplet-based ion sources, such as array of micromachined ultrasonic electrospray (AMUSE). Here, AMUSE is subject to DC and AC electric fields of varying amplitude and phase, with respect to a time-varying mechanical force driving the droplet formation. For the DC-charging case, a linear relationship is demonstrated between the charge carried by each droplet and an applied electric field magnitude, in agreement with previously reported experiments. For the AC-charging case, a judiciously-chosen phase-shift in the time-varying mechanical (driving ejection) and electrical (driving charge transport) signals allows for a significantly increased amount of charge, of desired polarity, to be pumped into a droplet upon ejection. Complementary experimental measurements of electrospray electrical current and charge-per-droplet, produced by the AMUSE ion source, are performed and support theoretical predictions for both DC- and AC-charging cases. The theoretical model and simulation tools provide a versatile and general analytical framework for fundamental investigations of coupled electrohydrodynamics and charge transport. The model also allows for the exploration of different configurations and operating modes to optimize charge separation in atmospheric pressure electrohydrodynamic ion sources under static and dynamic electrical and mechanical fields.
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Affiliation(s)
- Thomas P. Forbes
- G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - F. Levent Degertekin
- G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Andrei G. Fedorov
- G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332
- Parker H. Petit Institute for Bioengineering & Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332
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Kottke PA, Degertekin FL, Fedorov AG. Scanning mass spectrometry probe: a scanning probe electrospray ion source for imaging mass spectrometry of submerged interfaces and transient events in solution. Anal Chem 2010; 82:19-22. [PMID: 19904914 DOI: 10.1021/ac902102x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The scanning mass spectrometry (SMS) probe is a new electrospray ion source. Motivated by the need for untargeted chemical imaging of dynamic events in solution, we have exploited an approach to electrospray ionization (ESI) that allows continuous sampling from a highly localized volume (approximately picoliters) in a liquid environment, softly ionizes molecules in the sample to render them amenable for mass spectrometric analysis, and sends the ions to the mass spectrometer. The key underlying concepts for our approach are (1) treating the electrospray capillary inlet as a chemical scanning probe and (2) locating the electrospray point as close as possible to the sampling point, thus providing the shortest response time possible. This approach enables chemical monitoring or imaging of submerged interfaces, providing access to details of spatial heterogeneity and temporal changes within liquid samples. It also permits direct access to liquid/ liquid interfaces for ESI-MS analysis. In this letter we report the first demonstrations of these capabilities of the SMS probe and describe some of the probe's basic characteristics.
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