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Saupe M, Wiedemeier S, Gastrock G, Römer R, Lemke K. Flexible Toolbox of High-Precision Microfluidic Modules for Versatile Droplet-Based Applications. MICROMACHINES 2024; 15:250. [PMID: 38398978 PMCID: PMC10891953 DOI: 10.3390/mi15020250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/19/2024] [Accepted: 01/28/2024] [Indexed: 02/25/2024]
Abstract
Although the enormous potential of droplet-based microfluidics has been successfully demonstrated in the past two decades for medical, pharmaceutical, and academic applications, its inherent potential has not been fully exploited until now. Nevertheless, the cultivation of biological cells and 3D cell structures like spheroids and organoids, located in serially arranged droplets in micro-channels, has a range of benefits compared to established cultivation techniques based on, e.g., microplates and microchips. To exploit the enormous potential of the droplet-based cell cultivation technique, a number of basic functions have to be fulfilled. In this paper, we describe microfluidic modules to realize the following basic functions with high precision: (i) droplet generation, (ii) mixing of cell suspensions and cell culture media in the droplets, (iii) droplet content detection, and (iv) active fluid injection into serially arranged droplets. The robustness of the functionality of the Two-Fluid Probe is further investigated regarding its droplet generation using different flow rates. Advantages and disadvantages in comparison to chip-based solutions are discussed. New chip-based modules like the gradient, the piezo valve-based conditioning, the analysis, and the microscopy module are characterized in detail and their high-precision functionalities are demonstrated. These microfluidic modules are micro-machined, and as the surfaces of their micro-channels are plasma-treated, we are able to perform cell cultivation experiments using any kind of cell culture media, but without needing to use surfactants. This is even more considerable when droplets are used to investigate cell cultures like stem cells or cancer cells as cell suspensions, as 3D cell structures, or as tissue fragments over days or even weeks for versatile applications.
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Affiliation(s)
- Mario Saupe
- Institute for Bioprocessing and Analytical Measurement Techniques e.V., 37308 Heilbad Heiligenstadt, Germany; (S.W.); (G.G.); (R.R.); (K.L.)
- Department of Physical Chemistry and Microreaction Technologies, Technical University of Ilmenau, 98693 Ilmenau, Germany
| | - Stefan Wiedemeier
- Institute for Bioprocessing and Analytical Measurement Techniques e.V., 37308 Heilbad Heiligenstadt, Germany; (S.W.); (G.G.); (R.R.); (K.L.)
| | - Gunter Gastrock
- Institute for Bioprocessing and Analytical Measurement Techniques e.V., 37308 Heilbad Heiligenstadt, Germany; (S.W.); (G.G.); (R.R.); (K.L.)
| | - Robert Römer
- Institute for Bioprocessing and Analytical Measurement Techniques e.V., 37308 Heilbad Heiligenstadt, Germany; (S.W.); (G.G.); (R.R.); (K.L.)
| | - Karen Lemke
- Institute for Bioprocessing and Analytical Measurement Techniques e.V., 37308 Heilbad Heiligenstadt, Germany; (S.W.); (G.G.); (R.R.); (K.L.)
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Ling SD, Geng Y, Chen A, Du Y, Xu J. Enhanced single-cell encapsulation in microfluidic devices: From droplet generation to single-cell analysis. BIOMICROFLUIDICS 2020; 14:061508. [PMID: 33381250 PMCID: PMC7758092 DOI: 10.1063/5.0018785] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 12/09/2020] [Indexed: 05/24/2023]
Abstract
Single-cell analysis to investigate cellular heterogeneity and cell-to-cell interactions is a crucial compartment to answer key questions in important biological mechanisms. Droplet-based microfluidics appears to be the ideal platform for such a purpose because the compartmentalization of single cells into microdroplets offers unique advantages of enhancing assay sensitivity, protecting cells against external stresses, allowing versatile and precise manipulations over tested samples, and providing a stable microenvironment for long-term cell proliferation and observation. The present Review aims to give a preliminary guidance for researchers from different backgrounds to explore the field of single-cell encapsulation and analysis. A comprehensive and introductory overview of the droplet formation mechanism, fabrication methods of microchips, and a myriad of passive and active encapsulation techniques to enhance single-cell encapsulation efficiency were presented. Meanwhile, common methods for single-cell analysis, especially for long-term cell proliferation, differentiation, and observation inside microcapsules, are briefly introduced. Finally, the major challenges faced in the field are illustrated, and potential prospects for future work are discussed.
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Affiliation(s)
- Si Da Ling
- The State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
| | - Yuhao Geng
- The State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
| | - An Chen
- The State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
| | - Yanan Du
- Department of Biomedical Engineering, School of Medicine, Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China
| | - Jianhong Xu
- The State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
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Jankowski P, Kutaszewicz R, Ogończyk D, Garstecki P. A microfluidic platform for screening and optimization of organic reactions in droplets. J Flow Chem 2019. [DOI: 10.1007/s41981-019-00055-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Chen K, Sui C, Wu Y, Ao Z, Guo SS, Guo F. A digital acoustofluidic device for on-demand and oil-free droplet generation. NANOTECHNOLOGY 2019; 30:084001. [PMID: 30523921 DOI: 10.1088/1361-6528/aaf3fd] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We report a digital acoustofluidic device for on-demand and oil-free droplet generation. By applying a programmed radio frequency signal to a circular interdigital transducer, the dynamic focused acoustic pressure profiles generated rise up and dispense sample liquids from a reservoir to dynamically eject the droplets into the air. Our device allows droplets to be dispensed on demand with precisely controlled generation time and sequence, and accurate droplet volume. Moreover, we also demonstrate the generation of a droplet with a volume of 24 pL within 10 ms, as well as the encapsulation of a single cell into droplets. This acoustofluidic droplet generation technique is simple, biocompatible, and enables the on-demand droplet generation and encapsulation of many different biological materials with precise control, which is promising for single cell sampling and analysis applications.
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Affiliation(s)
- Keke Chen
- Key Laboratory of Artificial Micro- and Nano-structures of Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072, People's Republic of China
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Postek W, Kaminski TS, Garstecki P. A precise and accurate microfluidic droplet dilutor. Analyst 2018; 142:2901-2911. [PMID: 28676870 DOI: 10.1039/c7an00679a] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We demonstrate a microfluidic system for the precise (coefficient of variance between repetitions below 4%) and highly accurate (average difference from two-fold dilution below 1%) serial dilution of solutions inside droplets with a volume of ca. 1 μl. The two-fold dilution series can be prepared with the correlation coefficient as high as R2 = 0.999. The technique that we here describe uses hydrodynamic traps to precisely meter every droplet used in subsequent dilutions. We use only one metering trap to meter each and every droplet involved in the process of preparation of the dilution series. This eliminates the error of metering that would arise from the finite fidelity of fabrication of multiple metering traps. Metering every droplet at the same trap provides for high reproducibility of the volumes of the droplets, and thus high reproducibility of dilutions. We also present a device and method to precisely and accurately dilute one substance and simultaneously maintain the concentration of another substance throughout the dilution series without mixing their stock solutions. We compare the here-described precise and accurate dilution systems with a simple microdroplet dilutor that comprises several traps - each trap for a subsequent dilution. We describe the effect of producing more reproducible dilutions in a simple microdroplet dilutor thanks to the application of an alternating electric field.
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Affiliation(s)
- W Postek
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland.
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Zhu P, Wang L. Passive and active droplet generation with microfluidics: a review. LAB ON A CHIP 2016; 17:34-75. [PMID: 27841886 DOI: 10.1039/c6lc01018k] [Citation(s) in RCA: 495] [Impact Index Per Article: 61.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Precise and effective control of droplet generation is critical for applications of droplet microfluidics ranging from materials synthesis to lab-on-a-chip systems. Methods for droplet generation can be either passive or active, where the former generates droplets without external actuation, and the latter makes use of additional energy input in promoting interfacial instabilities for droplet generation. A unified physical understanding of both passive and active droplet generation is beneficial for effectively developing new techniques meeting various demands arising from applications. Our review of passive approaches focuses on the characteristics and mechanisms of breakup modes of droplet generation occurring in microfluidic cross-flow, co-flow, flow-focusing, and step emulsification configurations. The review of active approaches covers the state-of-the-art techniques employing either external forces from electrical, magnetic and centrifugal fields or methods of modifying intrinsic properties of flows or fluids such as velocity, viscosity, interfacial tension, channel wettability, and fluid density, with a focus on their implementations and actuation mechanisms. Also included in this review is the contrast among different approaches of either passive or active nature.
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Affiliation(s)
- Pingan Zhu
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China. and HKU-Zhejiang Institute of Research and Innovation (HKU-ZIRI), 311300, Hangzhou, Zhejiang, China
| | - Liqiu Wang
- Department of Mechanical Engineering, The University of Hong Kong, Hong Kong, China. and HKU-Zhejiang Institute of Research and Innovation (HKU-ZIRI), 311300, Hangzhou, Zhejiang, China
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Chong ZZ, Tan SH, Gañán-Calvo AM, Tor SB, Loh NH, Nguyen NT. Active droplet generation in microfluidics. LAB ON A CHIP 2016; 16:35-58. [PMID: 26555381 DOI: 10.1039/c5lc01012h] [Citation(s) in RCA: 121] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The reliable generation of micron-sized droplets is an important process for various applications in droplet-based microfluidics. The generated droplets work as a self-contained reaction platform in droplet-based lab-on-a-chip systems. With the maturity of this platform technology, sophisticated and delicate control of the droplet generation process is needed to address increasingly complex applications. This review presents the state of the art of active droplet generation concepts, which are categorized according to the nature of the induced energy. At the liquid/liquid interface, an energy imbalance leads to instability and droplet breakup.
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Affiliation(s)
- Zhuang Zhi Chong
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore
| | - Say Hwa Tan
- Queensland Micro- and Nanotechnology Centre, Griffith University, 170 Kessels Road QLD 4111, Brisbane, Australia.
| | - Alfonso M Gañán-Calvo
- Depto. de Ingeniería Aeroespacial y Mecánica de Fluidos, Universidad de Sevilla, E-41092 Sevilla, Spain.
| | - Shu Beng Tor
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore
| | - Ngiap Hiang Loh
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore
| | - Nam-Trung Nguyen
- Queensland Micro- and Nanotechnology Centre, Griffith University, 170 Kessels Road QLD 4111, Brisbane, Australia.
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Non-Linear Piezoelectric Actuator with a Preloaded Cantilever Beam. MICROMACHINES 2015. [DOI: 10.3390/mi6081066] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Tangen U, Sharma A, Wagler P, McCaskill JS. On demand nanoliter-scale microfluidic droplet generation, injection, and mixing using a passive microfluidic device. BIOMICROFLUIDICS 2015; 9:014119. [PMID: 25759752 PMCID: PMC4327917 DOI: 10.1063/1.4907895] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 01/29/2015] [Indexed: 05/10/2023]
Abstract
We here present and characterize a programmable nanoliter scale droplet-on-demand device that can be used separately or readily integrated into low cost single layer rapid prototyping microfluidic systems for a wide range of user applications. The passive microfluidic device allows external (off-the-shelf) electronically controlled pinch valves to program the delivery of nanoliter scale aqueous droplets from up to 9 different inputs to a central outlet channel. The inputs can be either continuous aqueous fluid streams or microliter scale aqueous plugs embedded in a carrier fluid, in which case the number of effective input solutions that can be employed in an experiment is no longer strongly constrained (100 s-1000 s). Both nanoliter droplet sequencing output and nanoliter-scale droplet mixing are reported with this device. Optimization of the geometry and pressure relationships in the device was achieved in several hardware iterations with the support of open source microfluidic simulation software and equivalent circuit models. The requisite modular control of pressure relationships within the device is accomplished using hydrodynamic barriers and matched resistance channels with three different channel heights, custom parallel reversible microfluidic I/O connections, low dead-volume pinch valves, and a simply adjustable array of external screw valves. Programmable sequences of droplet mixes or chains of droplets can be achieved with the device at low Hz frequencies, limited by device elasticity, and could be further enhanced by valve integration. The chip has already found use in the characterization of droplet bunching during export and the synthesis of a DNA library.
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Affiliation(s)
- Uwe Tangen
- Faculty of Chemistry and Biochemistry, Microsystems Chemistry and BioIT (BioMIP), Ruhr-University Bochum , 44780 Bochum, Germany
| | - Abhishek Sharma
- Faculty of Chemistry and Biochemistry, Microsystems Chemistry and BioIT (BioMIP), Ruhr-University Bochum , 44780 Bochum, Germany
| | - Patrick Wagler
- Faculty of Chemistry and Biochemistry, Microsystems Chemistry and BioIT (BioMIP), Ruhr-University Bochum , 44780 Bochum, Germany
| | - John S McCaskill
- Faculty of Chemistry and Biochemistry, Microsystems Chemistry and BioIT (BioMIP), Ruhr-University Bochum , 44780 Bochum, Germany
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