Abstract
The traditional power sources for generating droplets are bulky devices such as syringe pumps, constant pressure systems and so on, resulting in difficult integration with other microfluidic components. To overcome this limitation, we propose and develop a droplet generator with its power sources on a chip (22 × 21 × ~ 1 mm). The compact droplet generator consists of two ECF (electro-conjugate fluid) micropumps, a T-junction channel geometry made of SU-8, a water chamber and three I/O ports. In our methodology, the two ECF micropumps are used to pump the continuous phase fluid (oil) directly and the dispersed phase fluid (water) indirectly on a chip. ECF is a kind of functional and dielectric oil, which can generate a strong and active ECF jet when its corresponding electrodes are applied to high DC voltages. Our ECF micropump is composed of triangular prism and silt electrode pairs (TPSEs) and is able to control flow rates precisely on a chip. In our device, the water in oil droplet is formed by the T-junction geometry. Using MEMS technology, we successfully fabricate the droplet-generator-on-a-chip. Span 80 and dibutyl decanedioate (DBD, Tokyo Chemical Industry Co., Ltd) are used as the surfactant and one type of ECF, respectively. Prior to the characteristic experiments of the T-junction generator, we investigate viscosity, electrical conductivity and relative permittivity of the mixtures of DBD and Span 80 at different concentrations (0 wt%, 1 wt%, 3 wt% and 5 wt%). We also research the impact of the mixtures on the performance of ECF micropumps and the wettability of SU-8 fluidic channels. After that, we confirm the flow pattern diagrams of two-phase fluids, the generated droplet diameter and the droplet production rate for our droplet-generator. Therefore, our droplet generator powered by ECF micropumps can realize the droplet generation on a chip.
Similar content being viewed by others
References
Abate AR, Weitz DA (2011) Syringe-vacuum microfluidics: a portable technique to create monodisperse emulsions. Biomicrofluidics 5:014107
Abate AR, Mary P, van Steijn V, Weitz DA (2012a) Experimental validation of plugging during drop formation in a T-junction. Lab Chip 12:1516–1521
Abate AR, Mary P, van Steijn V, Weitz DA (2012b) Experimental validation of plugging during drop formation in a T-junction. Lab Chip 12:1516–1521
Baret J-C (2012) Surfactants in droplet-based microfluidics. Lab Chip 12:422–433
Bashir S, Bashir M, Rees JM, Zimmerman WBJ (2014) Dynamic wetting in microfluidic droplet formation. BioChip J 8:122–128
Berry JD, Neeson MJ, Dagastine RR, Chan DY, Tabor RF (2015) Measurement of surface and interfacial tension using pendant drop tensiometry. J Colloid Interface Sci 454:226–237
Dangla R, Gallaire F, Baroud CN (2010) Microchannel deformations due to solvent-induced PDMS swelling. Lab Chip 10:2972–2978
Dukhin AS, Goetz PJ (2006) How non-ionic “electrically neutral” surfactants enhance electrical conductivity and ion stability in non-polar liquids. J Electroanal Chem 588:44–50
Ekwall B, Nordensten C, Albanus L (1982) Toxicity of 29 plasticizers to HeLa cells in the MIT-24 system. Toxicology 24:199–210
Galas J-C, Bartolo D, Studer V (2009) Active connectors for microfluidic drops on demand. New J Phys 11:075027
García-Sánchez P, Ferney M, Ren Y, Ramos A (2012) Actuation of co-flowing electrolytes in a microfluidic system by microelectrode arrays. Microfluid Nanofluid 13:441–449
Iwai K, Shih KC, Lin X, Brubaker TA, Social RD, Lin L (2014) Finger-powered microfluidic systems using multilayer soft lithography and injection molding processes. Lab Chip 14:3790–3799
Kang X, Luo C, Wei Q, Xiong C, Chen Q, Chen Y, Ouyang Q (2013) Mass production of highly monodisperse polymeric nanoparticles by parallel flow focusing system. Microfluid Nanofluid 15:337–345
Kim J-W et al (2012) Tube-type micropump by using electro-conjugated fluid (ECF). Sens Actuators A 174:155–161
Kim J-w, Tanabe Y, Yokota S (2019) Comprehending electro-conjugate fluid (ECF) Jets by using the onsager effect. Sens Actuators A 295:266–273
Kobayashi I, Wada Y, Uemura K, Nakajima M (2010) Microchannel emulsification for mass production of uniform fine droplets: integration of microchannel arrays on a chip. Microfluid Nanofluid 8:255–262
Kuroboshi Y, Takemura K, Edamura K (2018) Understanding of electro-conjugate fluid flow with dibutyl decanedioate using numerical simulation—Calculating ion mobility using molecular dynamics simulation. Sens Actuators B Chem 255:448–453
Lan W, Li S, Xu J, Luo G (2012) A one-step microfluidic approach for controllable preparation of nanoparticle-coated patchy microparticles. Microfluid Nanofluid 13:491–498
Lim J, Caen O, Vrignon J, Konrad M, Taly V, Baret J-C (2015) Parallelized ultra-high throughput microfluidic emulsifier for multiplex kinetic assays. Biomicrofluidics 9:034101
Lin B-C, Su Y-C (2008) On-demand liquid-in-liquid droplet metering and fusion utilizing pneumatically actuated membrane valves. J Micromech Microeng 18:115005
Lippold BC, Gunder W, Lippold BH (1999) Drug release from diffusion pellets coated with the aqueous ethylcellulose dispersion aquacoat® ECD-30 and 20% dibutyl sebacate as plasticizer: partition mechanism and pore diffusion. Eur J Pharm Biopharm 47:27–32
Lorenz H, Despont M, Fahrni N, LaBianca N, Renaud P, Vettiger P (1997) SU-8: a low-cost negative resist for MEMS. J Micromech Microeng 7:121
Man J, Li Z, Li J, Chen H (2017) Phase inversion of slug flow on step surface to form high viscosity droplets in microchannel. Appl Phys Lett 110:181601
Mao Z, Yoshida K, Kim J-w (2019a) Developing O/O (oil-in-oil) droplet generators on a chip by using ECF (electro-conjugate fluid) micropumps. Sens Actuators B Chem 7:126669
Mao Z, Yoshida K, Kim J-w (2019b) Releasing large-area SU-8 structures without using any sacrificial layers. Microelectron Eng 212:53–60
Mao Z, Yoshida K, Kim J-w (2019c) A micro vertically-allocated SU-8 check valve and its characteristics. Microsyst Technol 25:245–255
Mao Z, Yoshida K, Kim J-w (2019d) Fast packaging by a partially-crosslinked SU-8 adhesive tape for microfluidic sensors and actuators. Sens Actuators A Phys 289:77–86
Martinez-Duarte R, Madou M (2011) SU-8 photolithography and its impact on microfluidics. Microfluid Nanofluid Handb 2011:231–268
Matsubara T, Huyn HH, Yoshida K, Kim J-w (2019) Development of MEMS-fabricated bidirectional ECF (electro-conjugate fluid) micropumps. Sens Actuators A 295:317–323
Murthy N, Xu M, Schuck S, Kunisawa J, Shastri N, Fréchet JM (2003) A macromolecular delivery vehicle for protein-based vaccines: acid-degradable protein-loaded microgels. Proc Natl Acad Sci 100:4995–5000
Nagaoka T, Mao Z, Takemura K, Yokota S, Kim JW (2019) ECF (electro-conjugate fluid) finger with bidirectional motion and its application to a flexible hand. Smart Mater Struct 28:025032
Nakashoji Y, Tanaka H, Tsukagoshi K, Hashimoto M (2017) A poly (dimethylsiloxane) microfluidic sheet reversibly adhered on a glass plate for the creation of emulsion droplets for droplet digital PCR. Electrophoresis 38:296–304
Ober MS et al (2018) Development of biphasic formulations for use in electrowetting-based liquid lenses with a high refractive index difference ACS combinatorial science 20:554–566
Okura N, Nakashoji Y, Koshirogane T, Kondo M, Tanaka Y, Inoue K, Hashimoto M (2017) A compact and facile microfluidic droplet creation device using a piezoelectric diaphragm micropump for droplet digital PCR platforms. Electrophoresis 38:26966
Pereira Mavis C. “Cosmetic composition.” U.S. Patent No. 4,981,845. 1 Jan 1991
Raghavan R, Qin J, Yeo LY, Friend JR, Takemura K, Yokota S, Edamura K (2009) Electrokinetic actuation of low conductivity dielectric liquids. Sens Actuators B Chem 140:287–294
Teste B, Jamond N, Ferraro D, Viovy J-L, Malaquin L (2015) Selective handling of droplets in a microfluidic device using magnetic rails. Microfluid Nanofluid 19:141–153
Tice JD, Lyon AD, Ismagilov RF (2004) Effects of viscosity on droplet formation and mixing in microfluidic channels. Anal Chim Acta 507:73–77
Vaidyanathan R, Dey S, Carrascosa LG, Shiddiky MJ, Trau M (2015) Alternating current electrohydrodynamics in microsystems: pushing biomolecules and cells around on surfaces. Biomicrofluidics 9:061501
Wang Y-N, Fu L-M (2018) Micropumps, and biomedical applications: a review. Microelectron Eng 195:121–138
Xu J, Li S, Tan J, Wang Y, Luo G (2006) Controllable preparation of monodisperse O/W and W/O emulsions in the same microfluidic device. Langmuir 22:7943–7946
Yang C-G, Liu Y-H, Di Y-Q, Xu Z-R (2015) Generation of two-dimensional concentration-gradient droplet arrays on a two-layer chip for the screening of protein crystallization conditions. Microfluid Nanofluid 18:493–501
Yannai S (2003) Dictionary of food compounds with CD-ROM: additives, flavors, and ingredients. CRC, London
Yokota S (2014) A review on micropumps from the viewpoint of volumetric power density. Mech Eng Rev 1:DSM0014
Yokota, Shinichi, Yasufumi Otsubo, and Kazuya Edamura. “Method of using electro-sensitive movable fluids.” U.S. Patent No. 6,495,071. 17 Dec 2002
Yuan Y, Lee TR (2013) Contact angle, and wetting properties. In: Surface science techniques. Springer, Berlin, pp 3–34
Zhao B, Cui X, Ren W, Xu F, Liu M, Ye Z-G (2017) A controllable and integrated pump-enabled microfluidic chip and its application in droplets generating. Sci Rep 7:11319
Zhu P, Wang L (2017) Passive and active droplet generation with microfluidics: a review. Lab Chip 17:34–75
Acknowledgements
A part of this work was supported by a JSPS KAKENHI Grant-in-Aid for Scientific Research (B), Grant number 18H01359.
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Mao, Z., Yoshida, K. & Kim, Jw. A droplet-generator-on-a-chip actuated by ECF (electro-conjugate fluid) micropumps. Microfluid Nanofluid 23, 130 (2019). https://doi.org/10.1007/s10404-019-2298-7
Received:
Accepted:
Published:
DOI: https://doi.org/10.1007/s10404-019-2298-7