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He Y, Qiao Y, Ding L, Cheng T, Tu J. Recent advances in droplet sequential monitoring methods for droplet sorting. BIOMICROFLUIDICS 2023; 17:061501. [PMID: 37969470 PMCID: PMC10645479 DOI: 10.1063/5.0173340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 10/23/2023] [Indexed: 11/17/2023]
Abstract
Droplet microfluidics is an attractive technology to run parallel experiments with high throughput and scalability while maintaining the heterogeneous features of individual samples or reactions. Droplet sorting is utilized to collect the desired droplets based on droplet characterization and in-droplet content evaluation. A proper monitoring method is critical in this process, which governs the accuracy and maximum frequency of droplet handling. Until now, numerous monitoring methods have been integrated in the microfluidic devices for identifying droplets, such as optical spectroscopy, mass spectroscopy, electrochemical monitoring, and nuclear magnetic resonance spectroscopy. In this review, we summarize the features of various monitoring methods integrated into droplet sorting workflow and discuss their suitable condition and potential obstacles in use. We aim to provide a systematic introduction and an application guide for choosing and building a droplet monitoring platform.
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Affiliation(s)
- Yukun He
- State Key Laboratory of Digital Medical Engineering, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Yi Qiao
- State Key Laboratory of Digital Medical Engineering, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Lu Ding
- State Key Laboratory of Digital Medical Engineering, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Tianguang Cheng
- State Key Laboratory of Digital Medical Engineering, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Jing Tu
- State Key Laboratory of Digital Medical Engineering, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
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2
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Zhang K, Xiang W, Liu J, Xie Z. Flexible droplet transportation and coalescence via controllable thermal fields. Anal Chim Acta 2023; 1277:341669. [PMID: 37604623 DOI: 10.1016/j.aca.2023.341669] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 07/03/2023] [Accepted: 07/26/2023] [Indexed: 08/23/2023]
Abstract
Flexible droplet transportation and coalescence are significant for lots of applications such as material synthesis and analytical detection. Herein, we present an effective method for controllable droplet transportation and coalescence via thermal fields. The device used for droplet manipulation is composed of a glass substrate with indium tin oxide-made microheaers and a microchannel with two transport branches and a central chamber, and it's manipulated by sequentially powering the microheaters located at the bottom of microchannel. The fluid will be unevenly heated when the microheater is actuated, leading to the formation of thermal buoyancy convection and the decrease of interfacial tension of fluids. Subsequently, the microdroplets can be transported from the inlets of microchannel to the target position by the buoyancy flow-induced Stokes drag. And the droplet migration velocity can be flexibly adjusted by changing the voltage applied on the microheater. After being transported to the center of central chamber, the coalescence behaviors of microdroplets can be triggered if the microheater located at the bottom of central chamber is continuously actuated. The droplet coalescence is the combined effect of decreased fluid interfacial tension, the shortened droplet distance by buoyancy flow and the increased instability of droplet under the elevated temperature. The droplet coalescence efficiency is also related to the voltage of microheater, by increasing the voltage from 3.5 V to 7 V, the needed time for droplet coalescence dramatically decrease from 220s to 1.4 s. Finally, by the droplet coalescence-triggered calcium hydroxide precipitation reaction, we demonstrate the applicability of the droplet manipulation method on specific sample detection. Therefore, this approach used for droplet transportation and coalescence can be attractive for many droplet-based applications such as analytical detection.
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Affiliation(s)
- Kailiang Zhang
- College of Mechanical and Electrical Engineering, Northeast Forestry University, Harbin, 150001, PR China
| | - Wei Xiang
- College of Mechanical and Electrical Engineering, Northeast Forestry University, Harbin, 150001, PR China
| | - Jiuqing Liu
- College of Mechanical and Electrical Engineering, Northeast Forestry University, Harbin, 150001, PR China
| | - Zhijie Xie
- College of Mechanical and Electrical Engineering, Northeast Forestry University, Harbin, 150001, PR China.
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Wang Y, Qian J. Femtosecond Laser Micromachining of the Mask for Acoustofluidic Device Preparation. ACS OMEGA 2023; 8:7838-7844. [PMID: 36873004 PMCID: PMC9979341 DOI: 10.1021/acsomega.2c07589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 02/03/2023] [Indexed: 06/18/2023]
Abstract
Surface acoustic wave (SAW)-based acoustofluidic devices have shown broad applications in microfluidic actuation and particle/cell manipulation. Conventional SAW acoustofluidic device fabrication generally includes photolithography and lift-off processes and thus requires accessing cleanroom facilities and expensive lithography equipment. In this paper, we report a femtosecond laser direct writing mask method for acoustofluidic device preparation. By micromachining of steel foil to form the mask and direct evaporation of metal on the piezoelectric substrate using the mask, the interdigital transducer (IDT) electrodes of the SAW device are generated. The minimum spatial periodicity of the IDT finger is about 200 μm, and the preparation for LiNbO3 and ZnO thin films and flexible PVDF SAW devices is verified. Meanwhile, we have demonstrated various microfluidic functions, including streaming, concentration, pumping, jumping, jetting, nebulization, and particle alignment using the fabricated acoustofluidic (ZnO/Al plate, LiNbO3) devices. Compared to the traditional manufacturing process, the proposed method omits spin coating, drying, lithography, developing, and lift-off processes and thus has advantages of simple, convenient, low cost, and environment friendliness.
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Affiliation(s)
- Yong Wang
- Department
of Mechanical Engineering, Hangzhou City
University, Hangzhou 310015, China
- The
State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, Hangzhou 310027, China
| | - Jingui Qian
- Anhui
Province Key Laboratory of Measuring Theory and Precision Instrument,
School of Instrument Science and Opto-Electronics Engineering, Hefei University of Technology, Hefei 230009, China
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Sui M, Dong H, Mu G, Xia J, Zhao J, Yang Z, Li T, Sun T, Grattan KTV. Droplet transportation by adjusting the temporal phase shift of surface acoustic waves in the exciter-exciter mode. LAB ON A CHIP 2022; 22:3402-3411. [PMID: 35899764 DOI: 10.1039/d2lc00402j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Droplet actuation using Surface Acoustic Wave (SAW) technology has been widely employed in 'lab-on-a-chip' applications, such as for on-chip Polymerase Chain Reactions. The current strategy uses the exciter-absorber mode (exciting a single InterDigital Transducer, IDT) to form a pure Travelling Surface Acoustic Wave (TSAW) and to actuate the droplet, where the velocity and direction of the droplet can be adjusted by controlling the on-off and amplitude of the excitation signals applied to a pair of IDTs. Herein, in a way that is different from using the exciter-absorber mode, we propose a method of actuating droplets by using the exciter-exciter mode (exciting a pair of IDTs simultaneously), where the velocity and directional adjustment of the droplet can be realized by changing only one excitation parameter for the signals (the temporal phase shift, θ), and the droplet velocity can also be significantly improved. Specifically, we report for the first time the equation of the vibration of the mixed waves (TSAW and Standing Surface Acoustic Wave (SSAW)) formed on the substrate surface using the exciter-exciter mode. This is analyzed theoretically, where it is shown in this work that the amplitude and direction of the TSAW component of the mixed waves can be adjusted by changing θ. Following that, the velocity and directional adjustment of the droplet has been realized by changing θ and the improvement of the droplet velocity has been verified on a one-dimensional SAW device, using this exciter-exciter mode. Moreover a series of experiments on droplet transportation, along different trajectories in an x-y plane, has been carried out using a two-dimensional SAW device and this has demonstrated the effectiveness of the θ changing-based approach. Here this exciter-exciter mode provides an alternative method for the transportation of droplets in 'lab-on-a-chip' applications.
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Affiliation(s)
- Mingyang Sui
- State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, 150001, Heilongjiang Province, China.
| | - Huijuan Dong
- State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, 150001, Heilongjiang Province, China.
| | - Guanyu Mu
- State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, 150001, Heilongjiang Province, China.
| | - Jingze Xia
- State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, 150001, Heilongjiang Province, China.
| | - Jie Zhao
- State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, 150001, Heilongjiang Province, China.
| | - Zhen Yang
- Institute of Orthopedics, Chinese PLA General Hospital, Beijing Key Laboratory of Regenerative Medicine in Orthopedics, Key Laboratory of Musculoskeletal Trauma & War Injuries PLA, Beijing, 100853, China.
| | - Tianlong Li
- State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, 150001, Heilongjiang Province, China.
| | - Tong Sun
- School of Mathematics, Computer Science and Engineering, City, University of London, London, EC1V 0HB, UK
| | - Kenneth T V Grattan
- State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, 150001, Heilongjiang Province, China.
- School of Mathematics, Computer Science and Engineering, City, University of London, London, EC1V 0HB, UK
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Chew NSL, Wong KS, Chang WS, Ooi CW, Yeo LY, Tan MK. Nanoscale plasma-activated aerosol generation for in situ surface pathogen disinfection. MICROSYSTEMS & NANOENGINEERING 2022; 8:41. [PMID: 35498339 PMCID: PMC9008002 DOI: 10.1038/s41378-022-00373-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 01/10/2022] [Accepted: 03/07/2022] [Indexed: 06/14/2023]
Abstract
Plasma treatment constitutes an efficient method for chemical-free disinfection. A spray-based system for dispensing plasma-activated aerosols onto surfaces would facilitate disinfection of complex and/or hidden surfaces inaccessible to direct line-of-sight (for example, UV) methods. The complexity and size of current plasma generators (for example, plasma jet and cometary plasma systems)-which prohibit portable operation, together with the short plasma lifetimes, necessitate a miniaturized in situ technique in which a source can be simultaneously activated and administered on-demand onto surfaces. Here, we demonstrate this possibility by combining two nanoscale technologies for plasma and aerosol generation into an integrated device that is sufficiently small and lightweight. Plasma is generated on a carpet of zinc oxide nanorods comprising a nanoneedle ensemble, which when raised to a high electric potential, constitutes a massive point charge array with near-singular electric fields to effect atmospheric breakdown. The plasma is then used to activate water transported through an underlying capillary wick, that is subsequently aerosolized under MHz-order surface acoustic waves. We show that the system, besides being amenable to miniaturization and hence integration into a chipscale device, leads to a considerable improvement in plasma-activation over its macroscale cometary discharge predecessor, with up to 20% and 127% higher hydrogen peroxide and nitrite ion concentrations that are respectively generated in the plasma-activated aerosols. This, in turn, leads to a 67% reduction in the disinfection time to achieve 95% bacterial load reduction, therefore demonstrating the potential of the technology as an efficient portable platform for on-demand field-use surface disinfection.
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Affiliation(s)
- Nicholas S. L. Chew
- Mechanical Engineering Discipline, School of Engineering, Monash University Malaysia, Bandar Sunway, Selangor Malaysia
| | - Kiing S. Wong
- Mechanical Engineering Discipline, School of Engineering, Monash University Malaysia, Bandar Sunway, Selangor Malaysia
| | - Wei S. Chang
- Mechanical Engineering Discipline, School of Engineering, Monash University Malaysia, Bandar Sunway, Selangor Malaysia
| | - Chien W. Ooi
- Chemical Engineering Discipline, School of Engineering, Monash University Malaysia, Bandar Sunway, Selangor Malaysia
| | - Leslie Y. Yeo
- Micro/Nanophysics Research Laboratory, RMIT University, Melbourne, VIC Australia
| | - Ming K. Tan
- Mechanical Engineering Discipline, School of Engineering, Monash University Malaysia, Bandar Sunway, Selangor Malaysia
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Nampoothiri KN, Satpathi NS, Sen AK. Surface acoustic wave-based generation and transfer of droplets onto wettable substrates. RSC Adv 2022; 12:23400-23410. [PMID: 36090390 PMCID: PMC9382648 DOI: 10.1039/d2ra04089a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Accepted: 08/09/2022] [Indexed: 11/21/2022] Open
Abstract
Fluid manipulation using surface acoustic waves (SAW) has been utilized as a promising technique in the field of microfluidics due to its numerous advantages, over other active techniques, such as low power requirement, facile fabrication methods, and non-invasive nature. Even though SAW-based generation of micron-sized droplets through atomization has been studied, the role of substrate wettability on the characteristics of the transferred droplets has not been explored to date. Here, we study the generation and effective transfer of micron-sized droplets using SAW onto wettable substrates whose water contact angles vary from 5° to 145°. The characteristics of transferred droplets after impacting the wettable substrates are characterized in terms of the contact line diameter and polydispersity index. A theoretical model is formulated to predict the initial average size of the transferred droplets on the wettable substrates of different contact angles. The variation of polydispersity and number density with contact angle is explained by considering droplet coalescence and bouncing. The relevance of the technique in biological assays is demonstrated by transferring droplets of streptavidin protein samples onto a substrate. Investigation of surface acoustic wave-based generation and transfer of droplets onto wettable substrates is carried out and explained in terms of polydispersity index. Transfer of biomolecules is demonstrated to highlight the technique.![]()
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Affiliation(s)
| | - Niladri Sekhar Satpathi
- Fluid Systems Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai-600036, India
| | - Ashis Kumar Sen
- Fluid Systems Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai-600036, India
- Micro Nano Bio Fluidics Group, Indian Institute of Technology Madras, Chennai-600036, India
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Ha NS, de Raad M, Han LZ, Golini A, Petzold CJ, Northen TR. Faster, better, and cheaper: harnessing microfluidics and mass spectrometry for biotechnology. RSC Chem Biol 2021; 2:1331-1351. [PMID: 34704041 PMCID: PMC8496484 DOI: 10.1039/d1cb00112d] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 07/01/2021] [Indexed: 12/14/2022] Open
Abstract
High-throughput screening technologies are widely used for elucidating biological activities. These typically require trade-offs in assay specificity and sensitivity to achieve higher throughput. Microfluidic approaches enable rapid manipulation of small volumes and have found a wide range of applications in biotechnology providing improved control of reaction conditions, faster assays, and reduced reagent consumption. The integration of mass spectrometry with microfluidics has the potential to create high-throughput, sensitivity, and specificity assays. This review introduces the widely-used mass spectrometry ionization techniques that have been successfully integrated with microfluidics approaches such as continuous-flow system, microchip electrophoresis, droplet microfluidics, digital microfluidics, centrifugal microfluidics, and paper microfluidics. In addition, we discuss recent applications of microfluidics integrated with mass spectrometry in single-cell analysis, compound screening, and the study of microorganisms. Lastly, we provide future outlooks towards online coupling, improving the sensitivity and integration of multi-omics into a single platform.
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Affiliation(s)
- Noel S Ha
- Biological Systems and Engineering, Lawrence Berkeley National Laboratory Berkeley CA USA
- US Department of Energy Joint BioEnergy Institute Emeryville CA USA
| | - Markus de Raad
- Environmental Genomics and Systems Biology, Biosciences, Lawrence Berkeley National Laboratory Berkeley CA USA
| | - La Zhen Han
- Environmental Genomics and Systems Biology, Biosciences, Lawrence Berkeley National Laboratory Berkeley CA USA
- US Department of Energy Joint Genome Institute Berkeley CA USA
| | - Amber Golini
- Environmental Genomics and Systems Biology, Biosciences, Lawrence Berkeley National Laboratory Berkeley CA USA
- US Department of Energy Joint Genome Institute Berkeley CA USA
| | - Christopher J Petzold
- Biological Systems and Engineering, Lawrence Berkeley National Laboratory Berkeley CA USA
- US Department of Energy Joint BioEnergy Institute Emeryville CA USA
| | - Trent R Northen
- Biological Systems and Engineering, Lawrence Berkeley National Laboratory Berkeley CA USA
- US Department of Energy Joint BioEnergy Institute Emeryville CA USA
- Environmental Genomics and Systems Biology, Biosciences, Lawrence Berkeley National Laboratory Berkeley CA USA
- US Department of Energy Joint Genome Institute Berkeley CA USA
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