1
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Zaman MA, Wu M, Ren W, Hesselink L. Impedance matching in optically induced dielectrophoresis: Effect of medium conductivity on trapping force. APPLIED PHYSICS LETTERS 2024; 125:051108. [PMID: 39100735 PMCID: PMC11296733 DOI: 10.1063/5.0223354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2024] [Accepted: 07/20/2024] [Indexed: 08/06/2024]
Abstract
An impedance analysis for optically induced dielectrophoresis is presented. A circuit model is developed for this purpose. The model parameters are fully defined in terms of the geometrical and material properties of the system. It is shown that trapping force can only be generated when the material properties follow certain impedance matching conditions. The impedance match factor is introduced to succinctly quantify the phenomenon. It is used to calculate bounds on the allowed electrical conductivity of the suspension medium. Results from the proposed model are found to be in good agreement with full-wave numerical simulations. By computing the acceptable set of material parameters with little computational cost, the presented analysis can streamline ODEP system design for various applications.
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Affiliation(s)
- Mohammad Asif Zaman
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA
| | - Mo Wu
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA
| | - Wei Ren
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA
| | - Lambertus Hesselink
- Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA
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2
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Jenne A, von der Ecken S, Moxley-Paquette V, Soong R, Swyer I, Bastawrous M, Busse F, Bermel W, Schmidig D, Kuehn T, Kuemmerle R, Al Adwan-Stojilkovic D, Graf S, Frei T, Monette M, Wheeler AR, Simpson AJ. Integrated Digital Microfluidics NMR Spectroscopy: A Key Step toward Automated In Vivo Metabolomics. Anal Chem 2023; 95:5858-5866. [PMID: 36996326 DOI: 10.1021/acs.analchem.2c04201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/01/2023]
Abstract
Toxicity testing is currently undergoing a paradigm shift from examining apical end points such as death, to monitoring sub-lethal toxicity in vivo. In vivo nuclear magnetic resonance (NMR) spectroscopy is a key platform in this endeavor. A proof-of-principle study is presented which directly interfaces NMR with digital microfluidics (DMF). DMF is a "lab on a chip" method allowing for the movement, mixing, splitting, and dispensing of μL-sized droplets. The goal is for DMF to supply oxygenated water to keep the organisms alive while NMR detects metabolomic changes. Here, both vertical and horizontal NMR coil configurations are compared. While a horizontal configuration is ideal for DMF, NMR performance was found to be sub-par and instead, a vertical-optimized single-sided stripline showed most promise. In this configuration, three organisms were monitored in vivo using 1H-13C 2D NMR. Without support from DMF droplet exchange, the organisms quickly showed signs of anoxic stress; however, with droplet exchange, this was completely suppressed. The results demonstrate that DMF can be used to maintain living organisms and holds potential for automated exposures in future. However, due to numerous limitations of vertically orientated DMF, along with space limitations in standard bore NMR spectrometers, we recommend future development be performed using a horizontal (MRI style) magnet which would eliminate practically all the drawbacks identified here.
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Affiliation(s)
- Amy Jenne
- Department of Chemistry, University of Toronto, 80. St. George Street, Toronto, Ontario M5S 3H6, Canada
- Environmental NMR Center, University of Toronto Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada
| | - Sebastian von der Ecken
- Department of Chemistry, University of Toronto, 80. St. George Street, Toronto, Ontario M5S 3H6, Canada
- Nicoya, B-29 King Street East, Kitchener, Ontario N2G 2K4, Canada
| | - Vincent Moxley-Paquette
- Environmental NMR Center, University of Toronto Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada
| | - Ronald Soong
- Environmental NMR Center, University of Toronto Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada
| | - Ian Swyer
- Department of Chemistry, University of Toronto, 80. St. George Street, Toronto, Ontario M5S 3H6, Canada
| | - Monica Bastawrous
- Environmental NMR Center, University of Toronto Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada
| | - Falko Busse
- Bruker BioSpin GmbH, Rudolf-Plank-Str. 23, 76275 Ettlingen, Germany
| | - Wolfgang Bermel
- Bruker BioSpin GmbH, Rudolf-Plank-Str. 23, 76275 Ettlingen, Germany
| | - Daniel Schmidig
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Till Kuehn
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Rainer Kuemmerle
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | | | - Stephan Graf
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Thomas Frei
- Bruker BioSpin AG, Industriestrasse 26, 8117 Fällanden, Switzerland
| | - Martine Monette
- Bruker Canada Ltd., 2800 High Point Drive, Milton, Ontario L9T 6P4, Canada
| | - Aaron R Wheeler
- Department of Chemistry, University of Toronto, 80. St. George Street, Toronto, Ontario M5S 3H6, Canada
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, 160 College Street, Toronto, Ontario M5S 3E1, Canada
- Institute for Biomedical Engineering, University of Toronto, 164 College Street, Toronto, Ontario M5S 3G9, Canada
| | - Andre J Simpson
- Department of Chemistry, University of Toronto, 80. St. George Street, Toronto, Ontario M5S 3H6, Canada
- Environmental NMR Center, University of Toronto Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada
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3
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Rocha DS, de Campos RP, Silva-Neto HA, Duarte-Junior GF, Bedioui F, Coltro WK. Digital microfluidic platform assembled into a home-made studio for sample preparation and colorimetric sensing of S-nitrosocysteine. Anal Chim Acta 2023; 1254:341077. [PMID: 37005016 DOI: 10.1016/j.aca.2023.341077] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 03/07/2023] [Accepted: 03/09/2023] [Indexed: 03/17/2023]
Abstract
Digital microfluidics (DMF) is a versatile lab-on-a-chip platform that allows integration with several types of sensors and detection techniques, including colorimetric sensors. Here, we propose, for the first time, the integration of DMF chips into a mini studio containing a 3D-printed holder with previously fixed UV-LEDs to promote sample degradation on the chip surface before a complete analytical procedure involving reagent mixture, colorimetric reaction, and detection through a webcam integrated on the equipment. As a proof-of-concept, the feasibility of the integrated system was successfully through the indirect analysis of S-nitrosocysteine (CySNO) in biological samples. For this purpose, UV-LEDs were explored to perform the photolytic cleavage of CySNO, thus generating nitrite and subproducts directly on DMF chip. Nitrite was then colorimetrically detected based on a modified Griess reaction, in which reagents were prepared through a programable movement of droplets on DMF devices. The assembling and the experimental parameters were optimized, and the proposed integration exhibited a satisfactory correlation with the results acquired using a desktop scanner. Under the optimal experimental conditions, the obtained CySNO degradation to nitrite was 96%. Considering the analytical parameters, the proposed approach revealed linear behavior in the CySNO concentration range between 12.5 and 400 μmol L-1 and a limit of detection equal to 2.8 μmol L-1. Synthetic serum and human plasma samples were successfully analyzed, and the achieved results did not statistically differ from the data recorded by spectrophotometry at the confidence level of 95%, thus indicating the huge potential of the integration between DMF and mini studio to promote complete analysis of lowmolecular weight compounds.
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4
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Tevlek A, Kecili S, Ozcelik OS, Kulah H, Tekin HC. Spheroid Engineering in Microfluidic Devices. ACS OMEGA 2023; 8:3630-3649. [PMID: 36743071 PMCID: PMC9893254 DOI: 10.1021/acsomega.2c06052] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 12/12/2022] [Indexed: 05/27/2023]
Abstract
Two-dimensional (2D) cell culture techniques are commonly employed to investigate biophysical and biochemical cellular responses. However, these culture methods, having monolayer cells, lack cell-cell and cell-extracellular matrix interactions, mimicking the cell microenvironment and multicellular organization. Three-dimensional (3D) cell culture methods enable equal transportation of nutrients, gas, and growth factors among cells and their microenvironment. Therefore, 3D cultures show similar cell proliferation, apoptosis, and differentiation properties to in vivo. A spheroid is defined as self-assembled 3D cell aggregates, and it closely mimics a cell microenvironment in vitro thanks to cell-cell/matrix interactions, which enables its use in several important applications in medical and clinical research. To fabricate a spheroid, conventional methods such as liquid overlay, hanging drop, and so forth are available. However, these labor-intensive methods result in low-throughput fabrication and uncontrollable spheroid sizes. On the other hand, microfluidic methods enable inexpensive and rapid fabrication of spheroids with high precision. Furthermore, fabricated spheroids can also be cultured in microfluidic devices for controllable cell perfusion, simulation of fluid shear effects, and mimicking of the microenvironment-like in vivo conditions. This review focuses on recent microfluidic spheroid fabrication techniques and also organ-on-a-chip applications of spheroids, which are used in different disease modeling and drug development studies.
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Affiliation(s)
- Atakan Tevlek
- METU
MEMS Research and Application Center, Ankara 06800, Turkey
| | - Seren Kecili
- The
Department of Bioengineering, Izmir Institute
of Technology, Urla, Izmir 35430, Turkey
| | - Ozge S. Ozcelik
- The
Department of Bioengineering, Izmir Institute
of Technology, Urla, Izmir 35430, Turkey
| | - Haluk Kulah
- METU
MEMS Research and Application Center, Ankara 06800, Turkey
- The
Department of Electrical and Electronics Engineering, Middle East Technical University, Ankara 06800, Turkey
| | - H. Cumhur Tekin
- METU
MEMS Research and Application Center, Ankara 06800, Turkey
- The
Department of Bioengineering, Izmir Institute
of Technology, Urla, Izmir 35430, Turkey
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5
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Vuille-Dit-Bille E, Deshmukh DV, Connolly S, Heub S, Boder-Pasche S, Dual J, Tibbitt MW, Weder G. Tools for manipulation and positioning of microtissues. LAB ON A CHIP 2022; 22:4043-4066. [PMID: 36196619 DOI: 10.1039/d2lc00559j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Complex three-dimensional (3D) in vitro models are emerging as a key technology to support research areas in personalised medicine, such as drug development and regenerative medicine. Tools for manipulation and positioning of microtissues play a crucial role in the microtissue life cycle from production to end-point analysis. The ability to precisely locate microtissues can improve the efficiency and reliability of processes and investigations by reducing experimental time and by providing more controlled parameters. To achieve this goal, standardisation of the techniques is of primary importance. Compared to microtissue production, the field of microtissue manipulation and positioning is still in its infancy but is gaining increasing attention in the last few years. Techniques to position microtissues have been classified into four main categories: hydrodynamic techniques, bioprinting, substrate modification, and non-contact active forces. In this paper, we provide a comprehensive review of the different tools for the manipulation and positioning of microtissues that have been reported to date. The working mechanism of each technique is described, and its merits and limitations are discussed. We conclude by evaluating the potential of the different approaches to support progress in personalised medicine.
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Affiliation(s)
- Emilie Vuille-Dit-Bille
- Centre Suisse d'Electronique et de Microtechnique SA, Neuchâtel, Switzerland.
- MicroBioRobotic Systems Laboratory, Institute of Mechanical Engineering, EPFL, Lausanne, Switzerland
| | - Dhananjay V Deshmukh
- Macromolecular Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland
- Institute for Mechanical Systems, Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland
| | - Sinéad Connolly
- Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, ETH Zürich, Zurich, Switzerland
| | - Sarah Heub
- Centre Suisse d'Electronique et de Microtechnique SA, Neuchâtel, Switzerland.
| | | | - Jürg Dual
- Institute for Mechanical Systems, Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland
| | - Mark W Tibbitt
- Macromolecular Engineering Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland
| | - Gilles Weder
- Centre Suisse d'Electronique et de Microtechnique SA, Neuchâtel, Switzerland.
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6
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Dwivedi RK, Muralidhar K. Contact line dynamics of a water drop spreading over a textured surface in the electrowetting-on-dielectric configuration. Phys Rev E 2022; 106:045111. [PMID: 36397474 DOI: 10.1103/physreve.106.045111] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 10/10/2022] [Indexed: 06/16/2023]
Abstract
Modeling the electrowetting process of a liquid droplet placed on a hydrophobic surface in an ambient environment has several challenges over and above those of basic spreading [F. Mugele, Soft Matter 5, 3377 (2009)10.1039/b904493k]. At an external voltage below the value that causes contact angle saturation, transient spreading is augmented by contact angle reduction defined by the Young-Lippmann equation. In addition, the macroscopic equilibrium contact angle and, therefore, the spreading rate could be altered by the surface hysteresis. Beyond the saturation point, spreading reveals additional features of higher complexity [Q. Vo and T. Tran, J. Fluid Mech. 925, A19 (2021)10.1017/jfm.2021.677]. These details have been examined from experiments as well as numerical simulation in the present work. Below the saturation point, the contact angle model of Dwivedi et al. [Phys. Rev. Fluids 7, 034002 (2022)10.1103/PhysRevFluids.7.034002] with the correction related to the electric field is seen to be applicable. Beyond saturation, the experimentally determined instantaneous contact angle distribution shows two distinct functionalities with respect to the contact line velocity. The first prevails from the onset of spreading until the spreading factor attains a peak value. The second trend is initiated with the retraction of the contact line. Except for differences in parametric values, the form of the contact angle model remains unchanged. Simulations in the postsaturation regime are shown to match experimental data in terms of the transient spreading factor, drop shapes, and the instantaneous contact angle. The role of the ground wire is found to be important and the three-phase contact line formed on it has been included in simulations. Spreading dynamics of the droplet have also been studied when the ground wire is kept at a distance of 40 μm from the apex of the drop. Simulations as well as experiments, show the propagation of a capillary wave between the ground wire and the three-phase contact line. For spreading over an uncoated polydimethylsiloxane (PDMS) surface, the contact line is trapped at local pinning sites, leading to additional distortions in the instantaneous shapes acquired by the interface.
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Affiliation(s)
- Raghvendra Kumar Dwivedi
- Department of Mechanical Engineering Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - K Muralidhar
- Department of Mechanical Engineering Indian Institute of Technology Kanpur, Kanpur 208016, India
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7
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Goralczyk A, Bhagwat S, Mayoussi F, Nekoonam N, Sachsenheimer K, Hou P, Kotz-Helmer F, Helmer D, Rapp BE. Application of Micro/Nanoporous Fluoropolymers with Reduced Bioadhesion in Digital Microfluidics. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:2201. [PMID: 35808037 PMCID: PMC9268009 DOI: 10.3390/nano12132201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 06/24/2022] [Accepted: 06/25/2022] [Indexed: 02/01/2023]
Abstract
Digital microfluidics (DMF) is a versatile platform for conducting a variety of biological and chemical assays. The most commonly used set-up for the actuation of microliter droplets is electrowetting on dielectric (EWOD), where the liquid is moved by an electrostatic force on a dielectric layer. Superhydrophobic materials are promising materials for dielectric layers, especially since the minimum contact between droplet and surface is key for low adhesion of biomolecules, as it causes droplet pinning and cross contamination. However, superhydrophobic surfaces show limitations, such as full wetting transition between Cassie and Wenzel under applied voltage, expensive and complex fabrication and difficult integration into already existing devices. Here we present Fluoropor, a superhydrophobic fluorinated polymer foam with pores on the micro/nanoscale as a dielectric layer in DMF. Fluoropor shows stable wetting properties with no significant changes in the wetting behavior, or full wetting transition, until potentials of 400 V. Furthermore, Fluoropor shows low attachment of biomolecules to the surface upon droplet movement. Due to its simple fabrication process, its resistance to adhesion of biomolecules and the fact it is capable of being integrated and exchanged as thin films into commercial DMF devices, Fluoropor is a promising material for wide application in DMF.
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Affiliation(s)
- Andreas Goralczyk
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110 Freiburg im Breisgau, Germany; (A.G.); (S.B.); (F.M.); (N.N.); (K.S.); (P.H.); (F.K.-H.); (B.E.R.)
| | - Sagar Bhagwat
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110 Freiburg im Breisgau, Germany; (A.G.); (S.B.); (F.M.); (N.N.); (K.S.); (P.H.); (F.K.-H.); (B.E.R.)
| | - Fadoua Mayoussi
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110 Freiburg im Breisgau, Germany; (A.G.); (S.B.); (F.M.); (N.N.); (K.S.); (P.H.); (F.K.-H.); (B.E.R.)
| | - Niloofar Nekoonam
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110 Freiburg im Breisgau, Germany; (A.G.); (S.B.); (F.M.); (N.N.); (K.S.); (P.H.); (F.K.-H.); (B.E.R.)
| | - Kai Sachsenheimer
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110 Freiburg im Breisgau, Germany; (A.G.); (S.B.); (F.M.); (N.N.); (K.S.); (P.H.); (F.K.-H.); (B.E.R.)
| | - Peilong Hou
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110 Freiburg im Breisgau, Germany; (A.G.); (S.B.); (F.M.); (N.N.); (K.S.); (P.H.); (F.K.-H.); (B.E.R.)
| | - Frederik Kotz-Helmer
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110 Freiburg im Breisgau, Germany; (A.G.); (S.B.); (F.M.); (N.N.); (K.S.); (P.H.); (F.K.-H.); (B.E.R.)
- Freiburg Materials Research Center (FMF), University of Freiburg, 79104 Freiburg im Breisgau, Germany
| | - Dorothea Helmer
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110 Freiburg im Breisgau, Germany; (A.G.); (S.B.); (F.M.); (N.N.); (K.S.); (P.H.); (F.K.-H.); (B.E.R.)
- Freiburg Materials Research Center (FMF), University of Freiburg, 79104 Freiburg im Breisgau, Germany
- Freiburg Center of Interactive Materials and Bioinspired Technologies (FIT), University of Freiburg, 79110 Freiburg im Breisgau, Germany
| | - Bastian E. Rapp
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110 Freiburg im Breisgau, Germany; (A.G.); (S.B.); (F.M.); (N.N.); (K.S.); (P.H.); (F.K.-H.); (B.E.R.)
- Freiburg Materials Research Center (FMF), University of Freiburg, 79104 Freiburg im Breisgau, Germany
- Freiburg Center of Interactive Materials and Bioinspired Technologies (FIT), University of Freiburg, 79110 Freiburg im Breisgau, Germany
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8
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Bansal S, Tokuda Y, Peasley J, Subramanian S. Electrically Induced Liquid Metal Droplet Bouncing. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:6996-7004. [PMID: 35617048 PMCID: PMC9178922 DOI: 10.1021/acs.langmuir.2c00577] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 05/10/2022] [Indexed: 06/15/2023]
Abstract
Liquid metals, including eutectic gallium-indium (EGaIn), have been explored for various planar droplet operations, including droplet splitting and merging, promoting their use in emerging areas such as flexible electronics and soft robotics. However, three-dimensional (3D) droplet operations, including droplet bouncing, have mostly been limited to nonmetallic liquids or aqueous solutions. This is the first study of liquid metal droplet bouncing using continuous AC electrowetting through an analytical model, computational fluid dynamics simulation, and empirical validation to the best of our knowledge. We achieved liquid metal droplet bouncing with a height greater than 5 mm with an actuation voltage of less than 10 V and a frequency of less than 5 Hz. We compared the bouncing trajectories of the liquid metal droplet for different actuation parameters. We found that the jumping height of the droplet increases as the frequency of the applied AC voltage decreases and its amplitude increases until the onset of instability. Furthermore, we model the attenuation dynamics of consecutive bouncing cycles of the underdamped droplet bouncing system. This study embarks on controlling liquid metal droplet bouncing electrically, thereby opening a plethora of new opportunities utilizing 3D liquid metal droplet operations for numerous applications such as energy harvesting, heat transfer, and radio frequency (RF) switching.
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Affiliation(s)
| | - Yutaka Tokuda
- City
University of Hong Kong, Kowloon 518057, Hong Kong, China
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9
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Kim T, Kim J, Kang JW, Kwon SB, Hong J. Compact Three-Dimensional Digital Microfluidic Platforms with Programmable Contact Charge Electrophoresis Actuation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:5759-5764. [PMID: 35482441 DOI: 10.1021/acs.langmuir.2c00360] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Digital microfluidics (DMF) has garnered considerable interest as a straightforward, rapid, and programmable technique for controlling microdroplets in various biological, chemical, and medicinal research disciplines. This study details the construction of compact and low-cost 3D DMF platforms with programmable contact charge electrophoresis (CCEP) actuations by employing electrode arrays composed of a small commercial pin socket and a 3D-printed housing. We demonstrate basic 3D droplet manipulation on the platform, including horizontal and vertical transport via lifting and climbing techniques, and droplet merging. Furthermore, phenolphthalein reaction and precipitation process are evaluated using the proposed 3D DMF manipulations as a proof of concept for chemical reaction-based analysis and synthesis. The threshold voltage (or electrical field) and maximum vertical transport velocity are quantified as a function of applied voltage and electrode distance to determine the CCEP actuation conditions for 3D droplet manipulations. The ease of manufacturing and flexibility of the proposed 3D DMF platform may provide an effective technique for programmable 3D manipulation of droplets in biochemical and medical applications, such as biochemical analysis and medical diagnostics.
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Affiliation(s)
- Taeyung Kim
- School of Mechanical Engineering, Soongsil University, 369 Sangdo-Ro, Dongjak-Gu, Seoul 06978, Republic of Korea
| | - Jaewook Kim
- School of Mechanical Engineering, Soongsil University, 369 Sangdo-Ro, Dongjak-Gu, Seoul 06978, Republic of Korea
| | - Jeon Woong Kang
- School of Mechanical Engineering, Soongsil University, 369 Sangdo-Ro, Dongjak-Gu, Seoul 06978, Republic of Korea
| | - Sun Beom Kwon
- School of Mechanical Engineering, Soongsil University, 369 Sangdo-Ro, Dongjak-Gu, Seoul 06978, Republic of Korea
| | - Jiwoo Hong
- School of Mechanical Engineering, Soongsil University, 369 Sangdo-Ro, Dongjak-Gu, Seoul 06978, Republic of Korea
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10
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Trampolining of Droplets on Hydrophobic Surfaces Using Electrowetting. MICROMACHINES 2022; 13:mi13030345. [PMID: 35334639 PMCID: PMC8953513 DOI: 10.3390/mi13030345] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 02/15/2022] [Accepted: 02/16/2022] [Indexed: 11/25/2022]
Abstract
Droplet detachment from solid surfaces is an essential part of many industrial processes. Electrowetting is a versatile tool for handling droplets in digital microfluidics, not only on plain surface but also in 3-D manner. Here, we report for the first time droplet trampolining using electrowetting. With the information collected by the real-time capacitor sensing system, we are able to synchronize the actuation signal with the spreading of the droplet upon impacting. Since electrowetting is applied each time the droplet impacts the substrate and switched off during recoiling of the droplet, the droplet gains additional momentum upon each impact and is able to jump higher during successive detachment. We have modelled the droplet trampolining behavior with a periodically driven harmonic oscillator, and the experiments showed sound agreement with theoretical predictions. The findings from this study will offer valuable insights to applications that demands vertical transportation of the droplets between chips arranged in parallel, or detachment of droplets from solid surfaces.
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11
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Droplet Transportation through an Orifice on Electrode for Digital Microfluidics Modulations. MICROMACHINES 2021; 12:mi12111385. [PMID: 34832797 PMCID: PMC8618053 DOI: 10.3390/mi12111385] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 11/06/2021] [Accepted: 11/10/2021] [Indexed: 11/17/2022]
Abstract
A digital microfluidic modular interface (chip-to-chip interface) which possesses an electrode with an orifice to vertically transport core-shell droplets is presented. The electrodes were geometrically designed to promote droplet deformation and suspension. The droplets were then applied with an electrical potential for insertion into and passage through the orifice. The concepts were tested with three types of droplets at the volume of 0.75~1.5 μL, which is usually difficult to transfer through an orifice. The integration of electrowetting on dielectric (EWOD) with paper-based microfluidics was demonstrated: the droplet could be transported within 10 s. More importantly, most of the core droplet (~97%) was extracted and passed through with only minimal shell droplets accompanying it.
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12
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Burkhart CT, Maki KL, Schertzer MJ. Coplanar Electrowetting-Induced Droplet Detachment from Radially Symmetric Electrodes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:8129-8136. [PMID: 32551661 DOI: 10.1021/acs.langmuir.0c01015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
This work demonstrates electrowetting-induced droplet detachment in air from coplanar electrodes using a single voltage pulse. It also presents two models to predict when this detachment will occur. Previous works approximated the minimum energy for detachment based on (i) adhesion work at the solid-liquid interface and (ii) interfacial energy changes along all three interfaces in the system. This investigation updates those models to include changes in gravitational potential energy during detachment and provides validation by testing predicted detachment thresholds against experimental observations. Droplets of varying volume were ejected from electrowetting devices with (i) radially symmetric four-part coplanar electrodes and (ii) single electrodes with a ground wire inserted directly into the droplet. All experiments were performed in air. Incorporation of gravitational potential energy improves predictions for critical electrowetting number and captures the observed increase in applied voltage required with increased droplet volume. These new models will be of particular benefit in three-dimensional digital microfluidics applications that manipulate droplets in air.
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Affiliation(s)
- Collin T Burkhart
- Mechanical Engineering, Rochester Institute of Technology, 76 Lomb Memorial Drive, Rochester, New York 14623, United States
| | - Kara L Maki
- School of Mathematical Sciences, Rochester Institute of Technology, 76 Lomb Memorial Drive, Rochester, New York 14623, United States
| | - Michael J Schertzer
- Mechanical Engineering, Rochester Institute of Technology, 76 Lomb Memorial Drive, Rochester, New York 14623, United States
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13
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Uzundal CB, Sahin O, Gokturk PA, Wu H, Mugele F, Ulgut B, Suzer S. X-ray Photoelectron Spectroscopy with Electrical Modulation Can Be Used to Probe Electrical Properties of Liquids and Their Interfaces at Different Stages. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:16989-16999. [PMID: 31794669 DOI: 10.1021/acs.langmuir.9b03134] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Operando X-ray photoelectron spectroscopy (o-XPS) has been used to record the binding energy shifts in the C 1s peak of a pristine poly(ethylene glycol) (PEG) liquid drop in an electrowetting on dielectric (EWOD) geometry and after exposing it to several high-voltage breakdown processes. This was achieved by recording XPS data while the samples were subjected to 10 V dc and ac (square-wave modulation) actuations to extract electrical information related to the liquid and its interface with the dielectric. Through analysis of the XPS data under ac actuation, a critical frequency of 170 Hz is extracted for the pristine PEG, which is translated to a resistance value of 14 MΩ for the liquid and a capacitance value of 60 pF for the dielectric, by the help of simulations using an equivalent circuit model and also by XPS analyses of a mimicking device under similar conditions. The same measurements yield an increased value of 23 MΩ for the resistance of the liquid after the breakdown by assuming that the capacitance of the dielectric stays constant. In addition, an asymmetry in polarity dependence is observed with respect to both the onset of the breakdown voltage and also the leakage behavior of the deteriorated (PEG + dielectric) system such that deviations are more pronounced at positive voltages. Both dc and ac behaviors of the postbreakdown system can also be simulated, but only by introducing an additional element, a diode or a polarity- and magnitude-dependent voltage source (VCVS), which might be attributed to negative charge accumulation at the interface. Measurements for a liquid mixture of PEG with 8% ionic liquid yields an almost 2 orders of magnitude smaller resistance for the drop as a result of the enhanced conductivity by the ions. Coupled with modeling, XPS measurements under dc and ac modulations enable probing unique electrochemical properties of liquid/solid interfaces.
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Affiliation(s)
- Can Berk Uzundal
- Department of Chemistry , Bilkent University , 06800 Ankara , Turkey
| | - Ozgur Sahin
- Department of Chemistry , Bilkent University , 06800 Ankara , Turkey
| | | | - Hao Wu
- Physics of Complex Fluids , University of Twente , 7522 NB , Enschede , The Netherlands
| | - Frieder Mugele
- Physics of Complex Fluids , University of Twente , 7522 NB , Enschede , The Netherlands
| | - Burak Ulgut
- Department of Chemistry , Bilkent University , 06800 Ankara , Turkey
| | - Sefik Suzer
- Department of Chemistry , Bilkent University , 06800 Ankara , Turkey
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14
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Huang S, Fair RB. Quantitative measurements of inorganic analytes on a digital microfluidics platform. SN APPLIED SCIENCES 2019. [DOI: 10.1007/s42452-019-1693-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
AbstractTwo methods were studied for selectively measuring the on-chip absorbance of trace sulfate analytes in droplets on a digital microfluidics (DMF) platform. In one method, the direction of measurement was perpendicular to the flat upper and lower surfaces of the DMF platform (vertical), and in the second method, the measurement direction was parallel to the DMF platform surfaces (horizontal). The channel height or the vertical light path length was 0.24 mm, and the droplet diameter was 1 mm. The DMF system employed a silicone oil transport medium whereby a thin, non-uniform oil layer formed between the droplet and the upper/lower plates which was unstable, resulting in randomly formed local oil lenses. The mobile oil lenses caused vertical absorbance measurement errors and uncertainties. The effects of the oil lenses were verified by simulation. Horizontal absorbance measurements were taken with embedded optical fibers (0.2 mm in diameter) aligned over the bottom chip surface in contact with the sides of the droplet, resulting in a horizontal light path length approximately three times that of the vertical light path. Because no oil lenses could form on the droplet’s sides, the stability of repeated horizontal measurements outperformed repeated vertical measurements made on the same droplet and on multiple droplets actuated into the measurement positions. Comparisons were based on measurement standard deviations and limits of detection (LOD). The following LODs and measurement standard deviations were achieved for horizontal measurements of multiple sulfate concentrations in 1.5 µl droplets: 7 ppm for sulfate (0.3–2.7%) and an R2 value of 0.957 from a least square data fit. Measurements on a commercial plate reader gave comparable results (200 µl liquid in each well, LOD equals 11 ppm, CV equals to 0.2–4%), even though the absorbance path was larger (0.7 mm). This LOD value means that the chip could detect 10.5 ng of sulfate. LOD values on vertical measurements were also similar, but large measurement errors from numerous outlier points yielded an R2 value of 0.735 and large average measurement standard deviations (36%).
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15
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Magnetic-Responsive Bendable Nozzles for Open Surface Droplet Manipulation. Polymers (Basel) 2019; 11:polym11111792. [PMID: 31683935 PMCID: PMC6918237 DOI: 10.3390/polym11111792] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 10/18/2019] [Accepted: 10/28/2019] [Indexed: 01/23/2023] Open
Abstract
The handling of droplets in a controlled manner is essential to numerous technological and scientific applications. In this work, we present a new open-surface platform for droplet manipulation based on an array of bendable nozzles that are dynamically controlled by a magnetic field. The actuation of these nozzles is possible thanks to the magnetically responsive elastomeric composite which forms the tips of the nozzles; this is fabricated with Fe3O4 microparticles embedded in a polydimethylsiloxane matrix. The transport, mixing, and splitting of droplets can be controlled by bringing together and separating the tips of these nozzles under the action of a magnet. Additionally, the characteristic configuration for droplet mixing in this platform harnesses the kinetic energy from the feeding streams; this provided a remarkable reduction of 80% in the mixing time between drops of liquids about eight times more viscous than water, i.e., 6.5 mPa/s, when compared against the mixing between sessile drops of the same fluids.
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16
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Jeong J, Lee JB, Chung SK, Kim D. Electromagnetic three dimensional liquid metal manipulation. LAB ON A CHIP 2019; 19:3261-3267. [PMID: 31478047 DOI: 10.1039/c9lc00503j] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
In this paper, we report three-dimensional (3-D) liquid metal manipulation using electromagnets, which can be applied to electrical switching applications. The liquid metal droplet was coated with iron (Fe) particles by chemical reaction with hydrochloric acid (HCl), and thus it became responsive to the magnetic field, becoming a magnetic liquid metal marble. Using electromagnets, the magnetic field was turned on and off on-demand. We investigated an average velocity and the maximum working distance of the horizontal and vertical electromagnetic field-driven manipulation of the magnetic liquid metal marble. Linear (1-D) and plane (2-D) manipulation of the marble was successfully demonstrated and 3-D manipulation was verified for electrical switching.
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Affiliation(s)
- Jinwon Jeong
- Department of Mechanical Engineering, Myongji University, Yongin, 449-728, Republic of Korea.
| | - Jeong-Bong Lee
- Department of Electrical Engineering, The University of Texas at Dallas, Richardson, Texas 75080, USA.
| | - Sang Kug Chung
- Department of Mechanical Engineering, Myongji University, Yongin, 449-728, Republic of Korea.
| | - Daeyoung Kim
- Department of Information and Communication Engineering, Korea Army Academy at Yeong-cheon, 770-849, South Korea.
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17
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Torabi M, Hemeda AA, Palko JW, Feng Y, Cao Y, Ma Y. Modes and break periods of electrowetting liquid bridge. Phys Rev E 2019; 100:033102. [PMID: 31640039 DOI: 10.1103/physreve.100.033102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Indexed: 06/10/2023]
Abstract
In this paper, we propose a microscale liquid oscillator using electrowetting-on-dielectric (EWOD). Specifically, a mesoscale liquid bridge (LB) between two horizontal surfaces with EWOD is considered. When EWOD is applied, the solid surface becomes more hydrophilic, and hence the contact angle (CA) is reduced. Following the activation of EWOD, the LB can remain connected or it can break into either symmetric or asymmetric shapes depending on the initial liquid volume and wettability of the two surfaces. The LB dynamics activated by EWOD is studied using the multibody dissipative particle dynamics (MDPD) method. Our numerical results show that the behavior of an LB under EWOD can be interpreted via three modes. In the first mode, the LB does not break after applying EWOD. In the second mode, the LB breaks and does not reform. The third mode happens when, depending on the interplay of the volume of the liquid and CA manipulation, the LB continuously breaks, recoils, and reforms. For asymmetric cases, it was observed that the LB may completely detach from one surface and may not reform. It was also observed that decreasing the wettability of a surface, for cases with a continuous breaking and reformation behavior, increases the connecting time interval and decreases the breaking time interval in one break-reform cycle. The results provided in this investigation facilitate fundamental understanding of LB dynamics and their application for the design of microscale liquid oscillators using EWOD.
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Affiliation(s)
- Mohsen Torabi
- School of Engineering, University of California, Merced, California 95343, USA
| | - Ahmed A Hemeda
- School of Engineering, University of California, Merced, California 95343, USA
- Aerospace Engineering Department, Cairo University, 12613 Egypt
| | - James W Palko
- School of Engineering, University of California, Merced, California 95343, USA
| | - Yu Feng
- Harbin Institute of Technology, Shenzhen, Guangdong 518055, People's Republic of China
| | - Yong Cao
- Harbin Institute of Technology, Shenzhen, Guangdong 518055, People's Republic of China
| | - Yanbao Ma
- School of Engineering, University of California, Merced, California 95343, USA
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18
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Zeng J, Zhang S, Tang K, Chen G, Yuan W, Tang Y. 3-D manipulation of a single nano-droplet on graphene with an electrowetting driving scheme: critical condition and tunability. NANOSCALE 2018; 10:16079-16086. [PMID: 30109343 DOI: 10.1039/c8nr03330g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The next generation of micro/nano-fluidic systems, featuring manipulation of a single nanoliter volume of a chemical reactant or bio-substance, is greatly dependent on the accurate manipulation of a single nano-droplet. In this paper, to resolve the lack of efficient methods for 3-D actuation of nano-droplets with high tunability, we proposed an electro-wetting-on-dielectric (EWOD) driving scheme on a graphene surface. The droplet could be actuated when the EWOD-saturated contact angle was reached, which determined the critical magnitude of the E-field. The droplet velocity agreed well with the vcom ∼ E1/2C-O law due to the film-detachment mechanism, which indicated the low viscous dissipation and good tunability of the proposed technique. The droplet velocity could also be tuned by changing the initial wettability of the graphene surface. Detailed examination of the liquid-solid interface revealed significant penetration of water molecules into the inner Helmholtz plane (IHP) before the induction of droplet detachment when the electric energy was converted into surface energy. For all the studied cases, the saturated contact angle served as a sufficient condition for the actuation of droplets.
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Affiliation(s)
- Jian Zeng
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA 92093, USA
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19
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Millington D, Norton S, Singh R, Sista R, Srinivasan V, Pamula V. Digital microfluidics comes of age: high-throughput screening to bedside diagnostic testing for genetic disorders in newborns. Expert Rev Mol Diagn 2018; 18:701-712. [PMID: 30004274 PMCID: PMC6481615 DOI: 10.1080/14737159.2018.1495076] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
INTRODUCTION Digital microfluidics (DMF) is an emerging technology with the appropriate metrics for application to newborn and high-risk screening for inherited metabolic disease and other conditions that benefit from early treatment. Areas covered: This review traces the development of electrowetting-based DMF technology toward the fulfillment of its promise to provide an inexpensive platform to conduct enzymatic assays and targeted biomarker assays at the bedside. The high-throughput DMF platform, referred to as SEEKER®, was recently authorized by the United States Food and Drug Administration to screen newborns for four lysosomal storage disorders (LSDs) and is deployed in newborn screening programs in the United States. The development of reagents and methods for LSD screening and results from screening centers are reviewed. Preliminary results from a more compact DMF device, to perform disease-specific test panels from small volumes of blood, are also reviewed. Literature for this review was sourced using principal author and subject searches in PubMed. Expert commentary: Newborn screening is a vital and highly successful public health program. DMF technology adds value to the current testing platforms that will benefit apparently healthy newborns with underlying genetic disorders and infants at-risk for conditions that present with symptoms in the newborn period.
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Affiliation(s)
- David Millington
- Department of Pediatrics, Duke University Medical Center, Durham, NC
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20
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Aydogan Gokturk P, Ulgut B, Suzer S. DC Electrowetting of Nonaqueous Liquid Revisited by XPS. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:7301-7308. [PMID: 29870259 DOI: 10.1021/acs.langmuir.8b01314] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Liquid poly(ethylene glycol) (molecular weight, ∼600 Da) with a low vapor pressure is used as droplets in an ultrahigh-vacuum X-ray photoelectron spectrometer (XPS) chamber with traditional electrowetting on dielectric (EWOD) device geometry. We demonstrate that, using XPS data, independent of the sign of the applied voltage, the droplet expands on the substrate with the application of a nonzero voltage and contracts back when the voltage is brought back to zero. However, the main focus of the present investigation is about tracing the electrical potential developments on and around the droplet, using the shifts in the binding energy positions of the core levels representative of the liquid and/or the substrate in an noninvasive and chemically specific fashion, under imposed electrical fields, with an aim of shedding light on numerous models employed for simulating EWOD phenomenon, as well as on certain properties of liquid/solid interfaces. While the lateral resolution of XPS does not permit to interrogate the interface directly, we explicitly show that critical information can be extracted by probing both sides of the interface simultaneously under external bias in the form of potential steps or direct current. We find that, even though no potential drop is observed at the metal-wire electrode/liquid interface, the entire potential drop develops across the liquid/solid-substrate interface, which is faster than our probe time window (∼100 ms) and is promptly complying with the applied bias until breakdown. No indication of band bending nor additional broadening can be observed in the C 1s peak of the liquid, even under electrical field strengths exceeding 107 V/m. Moreover and surprisingly, the liquid recovers within seconds after each catastrophic breakdown. All of these findings are new and expected to contribute significantly to a better understanding of certain physicochemical properties of liquid/solid interfaces.
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Affiliation(s)
| | - Burak Ulgut
- Department of Chemistry , Bilkent University , 06800 Ankara , Turkey
| | - Sefik Suzer
- Department of Chemistry , Bilkent University , 06800 Ankara , Turkey
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21
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Shi HH, Xiao Y, Ferguson S, Huang X, Wang N, Hao HX. Progress of crystallization in microfluidic devices. LAB ON A CHIP 2017; 17:2167-2185. [PMID: 28585942 DOI: 10.1039/c6lc01225f] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Microfluidic technology provides a unique environment for the investigation of crystallization processes at the nano or meso scale. The convenient operation and precise control of process parameters, at these scales of operation enabled by microfluidic devices, are attracting significant and increasing attention in the field of crystallization. In this paper, developments and applications of microfluidics in crystallization research including: crystal nucleation and growth, polymorph and cocrystal screening, preparation of nanocrystals, solubility and metastable zone determination, are summarized and discussed. The materials used in the construction and the structure of these microfluidic devices are also summarized and methods for measuring and modelling crystal nucleation and growth process as well as the enabling analytical methods are also briefly introduced. The low material consumption, high efficiency and precision of microfluidic crystallizations are of particular significance for active pharmaceutical ingredients, proteins, fine chemicals, and nanocrystals. Therefore, it is increasingly adopted as a mainstream technology in crystallization research and development.
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Affiliation(s)
- Huan-Huan Shi
- National Engineering Research Center of Industrial Crystallization Technology, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
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22
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Abstract
A three-dimensional (3D) tissue model has significant advantages over the conventional two-dimensional (2D) model. A 3D model mimics the relevant in-vivo physiological conditions, allowing a cell culture to serve as an effective tool for drug discovery, tissue engineering, and the investigation of disease pathology. The present reviews highlight the recent advances and the development of microfluidics based methods for the generation of cell spheroids. The paper emphasizes on the application of microfluidic technology for tissue engineering including the formation of multicellular spheroids (MCS). Further, the paper discusses the recent technical advances in the integration of microfluidic devices for MCS-based high-throughput drug screening. The review compares the various microfluidic techniques and finally provides a perspective for the future opportunities in this research area.
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23
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Zhang S, Huang J, Tang Y, Li S, Ge M, Chen Z, Zhang K, Lai Y. Understanding the Role of Dynamic Wettability for Condensate Microdrop Self-Propelling Based on Designed Superhydrophobic TiO 2 Nanostructures. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2017; 13. [PMID: 27152963 DOI: 10.1002/smll.201600687] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 03/29/2016] [Indexed: 05/06/2023]
Abstract
The ability to release the adhered drops on superhydrophobic surfaces is very important for self-cleaning, antifrosting/icing, microfluidic device, and heat transfer applications. In this paper, three types of in situ electrochemical anodizing TiO2 nanostructure films are rationally designed and fabricated on titanium substrates with special superwettability, viz., TiO2 nanotube arrays, irregular TiO2 nanotube arrays, and hierarchical TiO2 particle arrays (HTPA), and their corresponding behavior in condensate microdrop self-propelling (CMDSP) is investigated. Compared to the flat titanium counterpart, all three types of rough TiO2 samples demonstrate a uniform distribution of smaller microscale droplets. Among the treated surfaces, the HTPA possesses the highest condensate density, and more than 80% of the droplets possess a diameter below 10 μm. Theoretical analysis indicates that the feature is mainly due to the morphology and structure induced extremely low droplet adhesion on super-antiwetting TiO2 hierarchical surfaces, where the excess surface energy released from the migration leads to the self-propelling of merged microdrop. This work offers a way to rationally construct CMDSP surfaces with excellent self-cleaning, antifrosting/icing ability, and enhanced condensation heat transfer efficiency.
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Affiliation(s)
- Songnan Zhang
- National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, 215123, P. R. China
| | - Jianying Huang
- National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, 215123, P. R. China
| | - Yuxin Tang
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Shuhui Li
- National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, 215123, P. R. China
| | - Mingzheng Ge
- National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, 215123, P. R. China
| | - Zhong Chen
- School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Keqin Zhang
- National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, 215123, P. R. China
| | - Yuekun Lai
- National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, 215123, P. R. China
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Um T, Hong J, Im DJ, Lee SJ, Kang IS. Electrically Controllable Microparticle Synthesis and Digital Microfluidic Manipulation by Electric-Field-Induced Droplet Dispensing into Immiscible Fluids. Sci Rep 2016; 6:31901. [PMID: 27534580 PMCID: PMC4989170 DOI: 10.1038/srep31901] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 07/29/2016] [Indexed: 01/09/2023] Open
Abstract
The dispensing of tiny droplets is a basic and crucial process in a myriad of applications, such as DNA/protein microarray, cell cultures, chemical synthesis of microparticles, and digital microfluidics. This work systematically demonstrates droplet dispensing into immiscible fluids through electric charge concentration (ECC) method. It exhibits three main modes (i.e., attaching, uniform, and bursting modes) as a function of flow rates, applied voltages, and gap distances between the nozzle and the oil surface. Through a conventional nozzle with diameter of a few millimeters, charged droplets with volumes ranging from a few μL to a few tens of nL can be uniformly dispensed into the oil chamber without reduction in nozzle size. Based on the features of the proposed method (e.g., formation of droplets with controllable polarity and amount of electric charge in water and oil system), a simple and straightforward method is developed for microparticle synthesis, including preparation of colloidosomes and fabrication of Janus microparticles with anisotropic internal structures. Finally, a combined system consisting of ECC-induced droplet dispensing and electrophoresis of charged droplet (ECD)-driven manipulation systems is constructed. This integrated platform will provide increased utility and flexibility in microfluidic applications because a charged droplet can be delivered toward the intended position by programmable electric control.
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Affiliation(s)
- Taewoong Um
- Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-Dong, Nam-Gu, Pohang, Gyeongbuk, 37673, South Korea
| | - Jiwoo Hong
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-Dong, Nam-Gu, Pohang, Gyeongbuk, 37673, South Korea
| | - Do Jin Im
- Department of Chemical Engineering, Pukyong National University, 365 Sinseon-ro, Nam-gu, Busan 48547, South Korea
| | - Sang Joon Lee
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-Dong, Nam-Gu, Pohang, Gyeongbuk, 37673, South Korea
| | - In Seok Kang
- Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-Dong, Nam-Gu, Pohang, Gyeongbuk, 37673, South Korea
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Jiang D, Park SY. Light-driven 3D droplet manipulation on flexible optoelectrowetting devices fabricated by a simple spin-coating method. LAB ON A CHIP 2016; 16:1831-1839. [PMID: 27094708 DOI: 10.1039/c6lc00293e] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Technical advances in electrowetting-on-dielectric (EWOD) over the past few years have extended our attraction to three-dimensional (3D) devices capable of providing more flexibility and functionality with larger volumetric capacity than conventional 2D planar ones. However, typical 3D EWOD devices require complex and expensive fabrication processes for patterning and wiring of pixelated electrodes that also restrict the minimum droplet size to be manipulated. Here, we present a flexible single-sided continuous optoelectrowetting (SCOEW) device which is not only fabricated by a spin-coating method without the need for patterning and wiring processes, but also enables light-driven 3D droplet manipulations. To provide photoconductive properties, previous optoelectrowetting (OEW) devices have used amorphous silicon (a-Si) typically fabricated through high-temperature processes over 300 °C such as CVD or PECVD. However, most of the commercially-available flexible substrates such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) experience serious thermal deformation under such high-temperature processes. Because of this compatibility issue of conventional OEW devices with flexible substrates, light-driven 3D droplet manipulations have not yet been demonstrated on flexible substrates. Our study overcomes this compatibility issue by using a polymer-based photoconductive material, titanium oxide phthalocyanine (TiOPc) and thus SCOEW devices can be simply fabricated on flexible substrates through a low-cost, spin-coating method. In this paper, analytical studies were conducted to understand the effects of light patterns on static contact angles and EWOD forces. For experimental validations of our study, flexible SCOEW devices were successfully fabricated through the TiOPc-based spin-coating method and light-driven droplet manipulations (e.g. transportation, merging, and splitting) have been demonstrated on various 3D terrains such as inclined, vertical, upside-down, and curved surfaces. Our flexible SCOEW technology offers the benefits of device simplicity, flexibility, and functionality over conventional EWOD and OEW devices by enabling optical droplet manipulations on a 3D featureless surface.
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Affiliation(s)
- Dongyue Jiang
- Department of Mechanical Engineering, National University of Singapore, 117576, Singapore.
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Lee S, Lee S, Hwang H, Hong J, Lee S, Lee J, Chae Y, Lee T. Ultrafast single-droplet bouncing actuator with electrostatic force on superhydrophobic electrodes. RSC Adv 2016. [DOI: 10.1039/c6ra12092j] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The ultrafast bouncing motion of a liquid droplet has been investigated for droplet manipulation with a single droplet actuator using an electrostatic force for the first time.
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Affiliation(s)
- Seulah Lee
- Nanobio Device Laboratory
- School of Electrical and Electronic Engineering
- Yonsei University
- Seodaemun-Gu
- Republic of Korea
| | - Sanggeun Lee
- Nanobio Device Laboratory
- School of Electrical and Electronic Engineering
- Yonsei University
- Seodaemun-Gu
- Republic of Korea
| | - Hyunseok Hwang
- Mixed-Signal IC Laboratory
- School of Electrical and Electronic Engineering
- Yonsei University
- Seodaemun-Gu
- Republic of Korea
| | - Juree Hong
- Nanobio Device Laboratory
- School of Electrical and Electronic Engineering
- Yonsei University
- Seodaemun-Gu
- Republic of Korea
| | - Soonil Lee
- Nanobio Device Laboratory
- School of Electrical and Electronic Engineering
- Yonsei University
- Seodaemun-Gu
- Republic of Korea
| | - Jaehong Lee
- Nanobio Device Laboratory
- School of Electrical and Electronic Engineering
- Yonsei University
- Seodaemun-Gu
- Republic of Korea
| | - Youngcheol Chae
- Mixed-Signal IC Laboratory
- School of Electrical and Electronic Engineering
- Yonsei University
- Seodaemun-Gu
- Republic of Korea
| | - Taeyoon Lee
- Nanobio Device Laboratory
- School of Electrical and Electronic Engineering
- Yonsei University
- Seodaemun-Gu
- Republic of Korea
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27
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Blasutig IM. Miniaturization: The future of laboratory medicine. Clin Biochem 2016; 49:2-3. [DOI: 10.1016/j.clinbiochem.2015.11.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Revised: 11/10/2015] [Accepted: 11/12/2015] [Indexed: 10/22/2022]
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