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Tang Q, Song C, Wang Y, Zhang JH, Liu M, Xu Y, Wang C, Cui X. Drop-On-Demand Microdroplet Generation under Charge Injection by Corona Discharge. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:11966-11973. [PMID: 38809418 DOI: 10.1021/acs.langmuir.4c00403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2024]
Abstract
In printing, microreactors, and bioassays, the precise control of micrometer-scale droplet generation is essential but challenging, often restricted by the equipment and nozzles used in traditional methods. We introduce a needle-plate electrode corona discharge technique that injects charges into an oil layer, enabling the precise manipulation of droplet polarization and splitting. This method allows for meticulous adjustment of microdroplet formation regarding location, size, and quantity by modulating the discharge voltage, discharge time, and electrode positioning. It enables the immediate initiation and cessation of droplet production, thereby facilitating on-demand droplet generation. Our study on the voltage-dependent droplet stretch coefficient shows that as the voltage increases, the droplets transition from controlled splitting to regular Taylor cone-like ejections, eventually reaching the Rayleigh limit and fully breaking apart. These advancements significantly improve microfluidic droplet manipulation, offering considerable benefits for applications in targeted drug delivery, rapid disease diagnostics, and precise environmental monitoring.
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Affiliation(s)
- Qiang Tang
- Base for Innovative Methods Promotion Application and Demonstration of Anhui Province, Anhui University of Science and Technology, Huainan 232000, Anhui, China
- School of Artificial Intelligence, Anhui University of Science and Technology, Huainan 232000, Anhui, China
| | - Chengcheng Song
- School of Artificial Intelligence, Anhui University of Science and Technology, Huainan 232000, Anhui, China
| | - Yan Wang
- School of Artificial Intelligence, Anhui University of Science and Technology, Huainan 232000, Anhui, China
| | - Jia-Han Zhang
- School of Electronic Information Engineering, Inner Mongolia University, Hohhot 010021, China
- Collaborative Innovation Center of Advanced Microstructures, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
| | - Manfei Liu
- School of Artificial Intelligence, Anhui University of Science and Technology, Huainan 232000, Anhui, China
| | - Yunshan Xu
- School of Artificial Intelligence, Anhui University of Science and Technology, Huainan 232000, Anhui, China
| | - Chengjun Wang
- Base for Innovative Methods Promotion Application and Demonstration of Anhui Province, Anhui University of Science and Technology, Huainan 232000, Anhui, China
- School of Artificial Intelligence, Anhui University of Science and Technology, Huainan 232000, Anhui, China
| | - Xiaxia Cui
- Base for Innovative Methods Promotion Application and Demonstration of Anhui Province, Anhui University of Science and Technology, Huainan 232000, Anhui, China
- School of Artificial Intelligence, Anhui University of Science and Technology, Huainan 232000, Anhui, China
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Fang W, Tao Z, Li H, Ma Y, Yin S, Xu T, Wong T, Huang Y. Characteristics of Oil-in-Oil Emulsions under AC Electric Fields. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:2268-2277. [PMID: 38221735 DOI: 10.1021/acs.langmuir.3c03404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2024]
Abstract
Emulsions have been applied in a number of industries such as pharmaceutics, cosmetics, and food, which are also of great scientific interest. Although aqueous emulsions are commonly used in our daily life, oil-in-oil (o/o) emulsions also play an irreplaceable role in view of their unique physics and complementary applications. In this paper, we investigate typical behaviors of organic droplets surrounded by organic medium (o/o emulsions) with different functional groups controlled by the AC electric field. Droplet behaviors can be catalogued into five types: namely, "no effect", "movement", "deformation", "interface rupture", and "disorder". We identify the key dimensionless number Wee·Ca, combined with the channel geometry, for characterizing the typical behaviors in silicon oil/1,6-hexanediol diacrylate and mineral oil/1,6-hexanediol diacrylate emulsions. Unlike aqueous emulsion, the Maxwell-Wagner relaxation inhibits the electric effect and leads to an effective frequency, ranging from 0.5 to 3 kHz. The increasing viscosity of the droplet facilitates the escalation by promoting the shearing effect under the same flow conditions. Ethylene glycol droplets primarily show the efficient coalescence even at a low Wee·Ca, which is attributed to the attraction of free charges induced by the increasing conductivity. In 1,6-hexanediol diacrylate/silicon oil emulsion, the droplet tends to form a liquid film that expands into the entire channel due to the affinity of the droplet to the channel wall. A variety of elongated columns are observed to oscillate between the electrodes at high voltages. These findings can contribute to understanding the electrohydrodynamic physics in o/o emulsion and controlling droplet behaviors in a fast response, programmable, and high-throughput way. We expect that this droplet manipulation technology can be widely adopted in a broad range of chemical synthesis and biological and material science.
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Affiliation(s)
- Weidong Fang
- National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics, Research Institute of Aero-Engine, Beihang University, Beijing 100191, China
| | - Zhi Tao
- National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics, Research Institute of Aero-Engine, Beihang University, Beijing 100191, China
| | - Haiwang Li
- National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics, Research Institute of Aero-Engine, Beihang University, Beijing 100191, China
| | - Yuqian Ma
- University of California Irvine, Irvine 92697, California, United States
| | - Shuai Yin
- School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, China
| | - Tiantong Xu
- National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics, Research Institute of Aero-Engine, Beihang University, Beijing 100191, China
| | - Teckneng Wong
- School of Mechanical and Aerospace Engineering, Nanyang Technological University. 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Yi Huang
- National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics, Research Institute of Aero-Engine, Beihang University, Beijing 100191, China
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Fang W, Tao Z, Li H, Yin S, Xu T, Huang Y, Wong T. AC-electric-field-controlled multi-component droplet coalescence at microscale. LAB ON A CHIP 2023; 23:2341-2355. [PMID: 37078784 DOI: 10.1039/d3lc00086a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Droplet coalescence with fast response, high controllability and monodispersity has been widely investigated in industrial production and bioengineering. Especially for droplets with multiple components, programmable manipulation of such droplets is crucial for practical applications. However, precise control of the dynamics can be challenging, owing to the complex boundaries and the interfacial and fluidic properties. AC electric fields, with their fast response and high flexibility, have attracted our interest. We design and fabricate an improved flow-focusing microchannel configuration together with a non-contact type of electrode featuring asymmetric geometries, based on which we conduct systematic investigations of the AC-electric-field-controlled coalescence of multi-component droplets at the microscale. Parameters such as flow rates, component ratio, surface tension, electric permittivity and conductivity were given our attention. The results show that droplet coalescence in different flow parameters can be achieved in milliseconds by adjusting the electrical conditions, which shows high controllability. Specifically, both the coalescence region and reaction time can be adjusted by a combination of applied voltage and frequency, and unique merging phenomena have appeared. One is contact coalescence with the approach of paired droplets, while the other is squeezing coalescence, which occurs in the start position and promotes the merging process. The fluid properties, such as the electric permittivity, conductivity and surface tension, present a significant influence on merging behavior. The increasing relative dielectric constant leads to a dramatic reduction of the start merging voltage from the original 250 V to 30 V. The range of effective voltage for coalescence decreases with the addition of surfactant, offering a stricter and yet higher selectivity on electrical conditions, about 1500 V. The conductivity presents a negative correlation with the start merging voltage due to the reduction of the dielectric stress, from 400 V to 1500 V. Finally, we achieve the precise fabrication process of the Janus droplet via implementation of the proposed method, where the components of the droplets and the coalescence conditions are well controlled. Our results can serve as a potent methodology to decipher the physics of multi-component droplet electro-coalescence and contribute to applications in chemical synthesis, bioassay and material synthesis.
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Affiliation(s)
- Weidong Fang
- National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics, Research Institute of Aero-Engine, Beihang University, Beijing, 100191, China.
| | - Zhi Tao
- National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics, Research Institute of Aero-Engine, Beihang University, Beijing, 100191, China.
| | - Haiwang Li
- National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics, Research Institute of Aero-Engine, Beihang University, Beijing, 100191, China.
| | - Shuai Yin
- School of Mechanical and Power Engineering, Nanjing Tech University, Nanjing 211816, China
| | - Tiantong Xu
- National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics, Research Institute of Aero-Engine, Beihang University, Beijing, 100191, China.
| | - Yi Huang
- National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics, Research Institute of Aero-Engine, Beihang University, Beijing, 100191, China.
| | - Teckneng Wong
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore
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Triple-layered encapsulation through direct droplet impact. J Colloid Interface Sci 2022; 615:887-896. [DOI: 10.1016/j.jcis.2022.02.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Revised: 02/07/2022] [Accepted: 02/08/2022] [Indexed: 11/21/2022]
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Yin S, Huang Y, Li H, Wong TN. Dynamics of alternating current electric field–assisted non‐Newtonian droplet formation with geometry confinement. Electrophoresis 2022; 43:2120-2129. [DOI: 10.1002/elps.202200056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Revised: 04/06/2022] [Accepted: 04/22/2022] [Indexed: 11/11/2022]
Affiliation(s)
- Shuai Yin
- School of Mechanical and Aerospace Engineering Nanyang Technological University Singapore Singapore
| | - Yi Huang
- School of Mechanical and Aerospace Engineering Nanyang Technological University Singapore Singapore
- Research Institute of Aero‐Engine Beihang University Beijing P. R. China
| | - Haiwang Li
- Research Institute of Aero‐Engine Beihang University Beijing P. R. China
| | - Teck Neng Wong
- School of Mechanical and Aerospace Engineering Nanyang Technological University Singapore Singapore
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Yin S, Huang Y, Wong TN. Critical conditions for organic thread cutting under electric fields. SOFT MATTER 2021; 17:2913-2919. [PMID: 33587082 DOI: 10.1039/d0sm02078h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Conditions for triggering the cutting of organic samples under an AC electric field are investigated in a microchannel to explore the strategy for organic sample manipulation. Based on the nature of triggering and developing instability at liquid interfaces, in combination with an equivalent electric circuit model, a novel electric capillary number method is proposed as a comprehensive critical condition for the cutting. We uncover the physics behind cutting and non-cutting of an organic thread for different electric frequencies, electric properties of fluid, and width of the organic thread. The critical time required and the critical cutting position are studied to offer guidelines for accurate cutting. Higher electric frequency and higher permittivity of the aqueous phase surrounding the organic phase can reduce the voltage required for cutting. In summary, the newly defined electric capillary number is proved to be a comprehensive criterion for determining the cutting phenomena, which is capable of considering the interfacial tension, the electric permittivity and the electric field strength applied. The results offer applicable references for achieving efficient and accurate cutting of organic samples in practical applications.
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Affiliation(s)
- Shuai Yin
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
| | - Yi Huang
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore. and Research Institute of Aero-Engine, Beihang University, No. 37 XueYuan Road, Haidian District, Beijing, 100083, China
| | - Teck Neng Wong
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
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