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Research on the Centrifugal Driving of a Water-in-Oil Droplet in a Microfluidic Chip with Spiral Microchannel. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12094362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Combining the advantages of droplet-based microfluidics and centrifugal driving, a method for centrifugally driving W/O droplets with spiral microchannel is proposed in this paper. A physical model of droplet flow was established to study the flow characteristics of the W/O droplet in the spiral microchannel driven by centrifugal force, and kinematic analysis was performed based on the rigid body assumption. Then, the theoretical formula of droplet flow rate was obtained. The theoretical value was compared with the actual value measured in the experiments. The result shows that the trend of the theoretical value is consistent with the measured value, and the theoretical value is slightly larger than the experimentally measured value caused by deformation. Moreover, it is found that the mode of centrifugal driving with spiral microchannel has better flow stability than the traditional centrifugal driving structure. A larger regulation speed range can be achieved by adjusting the motor speed without using expensive equipment or precise instruments. This study can provide a basis and theoretical reference for the development of droplet-based centrifugal microfluidic chips.
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Qin F, Zhang K, Lin B, Su P, Jia Z, Xi K, Ye J, Gu S. Solution for Mass Production of High-Throughput Digital Microfluidic Chip Based on a-Si TFT with In-Pixel Boost Circuit. MICROMACHINES 2021; 12:mi12101199. [PMID: 34683251 PMCID: PMC8541461 DOI: 10.3390/mi12101199] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Accepted: 09/28/2021] [Indexed: 11/16/2022]
Abstract
As one of the most popular research hotspot of lab-on-chip, digital microfluidic (DMF) technology based on the principle of electrowetting has unique advantages of high-precision, low cost and programmable control. However, due to the limitation of electrodes number, the throughput is hard to further upgrade. Therefore, active matrix electrowetting-on-dielectric (AM-EWOD) technology is a solution to acquire larger scale of driving electrodes. However, the process of manufacturing of AM-EWOD based on thin-film-transistor (TFT) is complex and expensive. Besides, the driving voltage of DMF chip is usually much higher than that of common display products.In this paper, a solution for mass production of AM-EWOD based on amorphous silicon (a-Si) is provided. Samples of 32 × 32 matrix AM-EWOD chips was designed and manufactured. A boost circuit was integrated into the pixel, which can raise the pixel voltage up by about 50%. Customized designed Printed Circuit Board (PCB) was used to supply the timing signals and driving voltage to make the motion of droplets programmable. The process of moving, mixing and generation of droplets was demonstrated.The minimum voltage in need was about 20 V and a velocity of up to 96 mm/s was achieved. Such an DMF device with large-scale matrix and low driving voltage will be very suitable for POCT applications.
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Affiliation(s)
- Feng Qin
- School of Electronic Science & Engineering, Nanjing University, Nanjing 210023, China; (F.Q.); (J.Y.)
- Shanghai AVIC Optoelectronics, 3388 Huaning Rd., Minhang District, Shanghai 201108, China;
| | - Kaidi Zhang
- Shanghai Tianma Micro-Electronics, 889 Huiqing Rd., Pudong District, Shanghai 201201, China; (K.Z.); (B.L.); (P.S.); (Z.J.)
| | - Baiquan Lin
- Shanghai Tianma Micro-Electronics, 889 Huiqing Rd., Pudong District, Shanghai 201201, China; (K.Z.); (B.L.); (P.S.); (Z.J.)
| | - Ping Su
- Shanghai Tianma Micro-Electronics, 889 Huiqing Rd., Pudong District, Shanghai 201201, China; (K.Z.); (B.L.); (P.S.); (Z.J.)
| | - Zhenyu Jia
- Shanghai Tianma Micro-Electronics, 889 Huiqing Rd., Pudong District, Shanghai 201201, China; (K.Z.); (B.L.); (P.S.); (Z.J.)
| | - Kerui Xi
- Shanghai AVIC Optoelectronics, 3388 Huaning Rd., Minhang District, Shanghai 201108, China;
| | - Jiandong Ye
- School of Electronic Science & Engineering, Nanjing University, Nanjing 210023, China; (F.Q.); (J.Y.)
| | - Shulin Gu
- School of Electronic Science & Engineering, Nanjing University, Nanjing 210023, China; (F.Q.); (J.Y.)
- Correspondence:
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Swyer I, Fobel R, Wheeler AR. Velocity Saturation in Digital Microfluidics. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:5342-5352. [PMID: 30958677 DOI: 10.1021/acs.langmuir.9b00220] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In digital microfluidics, discrete droplets of fluid are made to move on an open surface with no microchannels. These systems are commonly operated by application of electrical driving forces to an array of electrodes. While these driving forces are well characterized, the dissipative forces opposing droplet movement have not been as thoroughly examined. In recognition of this deficit, we used force-velocity plots to characterize droplet movement in digital microfluidics, which was found to be consistent with a simple theoretical framework for understanding dissipation effects for droplets in two-plate, air-filled devices. Interestingly, in some conditions, a previously unreported ″velocity saturation″ effect was observed. When examined across a range of different liquids, the forces at which this saturation occurs seem to be lower for liquids with smaller surface tensions. Furthermore, when driven at forces that cause saturation, physical phenomena are observed that are akin to what has been reported for stationary droplets in the electrowetting literature. These phenomena are detrimental to device performance, leading to a new "force window" approach that delineates the optimum operation conditions for different liquids. We propose that these findings may be useful for a wide range of applications for experts and new users alike in this growing field.
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Affiliation(s)
- Ian Swyer
- Department of Chemistry , University of Toronto , 80 St. George Street , Toronto , ON M5S 3H6 , Canada
| | - Ryan Fobel
- Donnelly Centre for Cellular and Biomolecular Research , University of Toronto , 160 College Street , Toronto , ON M5S 3E1 , Canada
| | - Aaron R Wheeler
- Department of Chemistry , University of Toronto , 80 St. George Street , Toronto , ON M5S 3H6 , Canada
- Donnelly Centre for Cellular and Biomolecular Research , University of Toronto , 160 College Street , Toronto , ON M5S 3E1 , Canada
- Institute for Biomaterials and Biomedical Engineering , University of Toronto , 164 College Street , Toronto , ON M5S 3G9 , Canada
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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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Yafia M, Emran BJ, Najjaran H. Digital Microfluidic Systems: Fundamentals, Configurations, Techniques, and Applications. MICROFLUIDICS: FUNDAMENTAL, DEVICES AND APPLICATIONS 2018:175-209. [DOI: 10.1002/9783527800643.ch5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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Li Y, Li H, Baker RJ. A Low-Cost and High-Resolution Droplet Position Detector for an Intelligent Electrowetting on Dielectric Device. ACTA ACUST UNITED AC 2015; 20:663-9. [DOI: 10.1177/2211068214566940] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Indexed: 11/16/2022]
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't Mannetje DJCM, Mugele F, van den Ende D. Stick-Slip to Sliding Transition of Dynamic Contact Lines under AC Electrowetting. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:15116-15121. [PMID: 24219094 DOI: 10.1021/la402761m] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We show that at low velocities the dynamics of a contact line of a water drop moving over a Teflon-like surface under ac electrowetting must be described as stick-slip motion, rather than one continuous movement. At high velocities we observe a transition to a slipping regime. In the slipping regime the observed dependence of the contact angle is well described by a linearization of both the hydrodynamic and the molecular-kinetic model for the dynamic contact line behavior. The overall geometry of the drop also has a strong influence on the contact angle: if the drop is confined to a disk-like shape with radius R, much larger than the capillary length, and height h, smaller than the capillary length, the advancing angle increases steeper with velocity as the aspect ratio h/R is smaller. Although influence of the flow field near a contact line on the contact angle behavior has also been observed in other experiments, these observations do not fit either model. Finally, in our ac experiments no sudden increase of the hysteresis beyond a certain voltage and velocity was observed, as reported by other authors for a dc voltage, but instead we find with increasing voltage a steady decrease of the hysteresis.
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Affiliation(s)
- D J C M 't Mannetje
- Physics of Complex Fluids, MESA+ Institute for Nanotechnology, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands
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Schertzer MJ, Ahamed MJ, Ben-Mrad R, Lea P, Sullivan PE. Characterizing the surface quality and droplet interface shape for microarray plates. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:9961-9966. [PMID: 22671939 DOI: 10.1021/la302091t] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The variation in the surface quality of microarray plates was examined by measuring the contact angles of 480 droplets on five microarray plates. It was found that the measured contact angle did not accurately predict the droplet shape for moderate Bond numbers (~0.5 ≤ N(B) ≤ 5). By defining an apparent contact angle using the ratio of the contact radius to the height, the variance in the predicted interface shape decreased by greater than a factor of 3 for both local and globally averaged characteristics. The error in the predicted droplet height was also reduced by 3 orders of magnitude.
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Affiliation(s)
- M J Schertzer
- Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Ontario, Canada
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Gupta R, Sheth DM, Boone TK, Sevilla AB, Fréchette J. Impact of pinning of the triple contact line on electrowetting performance. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:14923-14929. [PMID: 22050215 DOI: 10.1021/la203320g] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Pinning of the triple contact line adversely affects electrowetting on dielectric. Electrowetting response of substrates with contact angle hysteresis ranging from 1° to 30° has been characterized, and the results are interpreted within the framework of electromechanics corrected for pinning. The relationship between contact angle hysteresis, threshold potential for liquid actuation, and electrowetting hysteresis is quantified. Our results demonstrate that a modified electrowetting equation, based on balance of forces (including the pinning forces) acting on the triple contact line and on the drop, describes the electrowetting response of substrates with significant contact angle hysteresis. Finally, the surface properties of PDMS Sylgard 184 were found to be influenced by the electric field.
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Affiliation(s)
- Rohini Gupta
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA
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Nelson WC, Sen P, Kim CJCJ. Dynamic contact angles and hysteresis under electrowetting-on-dielectric. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:10319-10326. [PMID: 21751778 PMCID: PMC3157320 DOI: 10.1021/la2018083] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
By designing and implementing a new experimental method, we have measured the dynamic advancing and receding contact angles and the resulting hysteresis of droplets under electrowetting-on-dielectric (EWOD). Measurements were obtained over wide ranges of applied EWOD voltages, or electrowetting numbers (0 ≤ Ew ≤ 0.9), and droplet sliding speeds, or capillary numbers (1.4 × 10(-5) ≤ Ca ≤ 6.9 × 10(-3)). If Ew or Ca is low, dynamic contact angle hysteresis is not affected much by the EWOD voltage or the sliding speed; that is, the hysteresis increases by less than 50% with a 2 order-of-magnitude increase in sliding speed when Ca < 10(-3). If both Ew and Ca are high, however, the hysteresis increases with either the EWOD voltage or the sliding speed. Stick-slip oscillations were observed at Ew > 0.4. Data are interpreted with simplified hydrodynamic (Cox-Voinov) and molecular-kinetic theory (MKT) models; the Cox-Voinov model captures the trend of the data, but it yields unreasonable fitting parameters. MKT fitting parameters associated with the advancing contact line are reasonable, but a lack of symmetry indicates that a more intricate model is required.
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Affiliation(s)
- Wyatt C Nelson
- Mechanical and Aerospace Engineering Department, University of California, Los Angeles, Los Angeles, California 90095, United States.
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Klarman D, Andelman D, Urbakh M. A model of electrowetting, reversed electrowetting, and contact angle saturation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:6031-6041. [PMID: 21510663 DOI: 10.1021/la2004326] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
While electrowetting has many applications, it is limited at large voltages by contact angle saturation, a phenomenon that is still not well understood. We propose a generalized approach for electrowetting that, among other results, can shed new light on contact angle saturation. The model assumes the existence of a minimum (with respect to the contact angle) in the electric energy and accounts for a quadratic voltage dependence ∼U(2) in the low-voltage limit, compatible with the Young-Lippmann formula, and an ∼U(-2) saturation at the high-voltage limit. Another prediction is the surprising possibility of a reversed electrowetting regime, in which the contact angle increases with applied voltage. By explicitly taking into account the effect of the counter-electrode, our model is shown to be applicable to several AC and DC experimental electrowetting-on-dielectric (EWOD) setups. Several features seen in experiments compare favorably with our results. Furthermore, the AC frequency dependence of EWOD agrees quantitatively with our predictions. Our numerical results are complemented with simple analytical expressions for the saturation angle in two practical limits.
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Affiliation(s)
- Dan Klarman
- Raymond & Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Ramat Aviv 69978, Tel Aviv, Israel
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Milne AJB, Elliott JAW, Zabeti P, Zhou J, Amirfazli A. Model and experimental studies for contact angles of surfactant solutions on rough and smooth hydrophobic surfaces. Phys Chem Chem Phys 2011; 13:16208-19. [DOI: 10.1039/c1cp20593e] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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