LED-based opto-wetting and fluidic transport for droplet mixing
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Light energy is utilized as an extensive tool for actuation of fluid flow in microfluidic devices. We report a novel method of droplet actuation using LED (light-emitting diode) that can be utilized for microfluidic mixing applications. This low power LED which emits light of peak wavelength 395 nm delivering luminous power of less than 300 millicandela (mcd) was used to create an interfacial tension gradient on solid–liquid interface containing photoresponsive molecule of azobenzene (C12H10N2). LED-induced photoisomerization of azobenzene creates a spatial gradient in interfacial energy on the solid–liquid interface, which enhances the droplet movement. The concept of LED-enhanced fluidic actuation was demonstrated using droplets of water, urine, blood serum over photoresponsive substrate. The substrates were prepared by coating the surface of silicon substrate with azobenzene dissolved in silicone resin solution. Detailed experimental characterization of LED-actuated droplet velocity was performed, where the effect of parameters such as frequency of light actuation, droplet volume, concentration of azobenzene was evaluated. Droplet transport of DI water (de-ionized) of volume 60 µL was achieved at a velocity of 160 µm/s corresponding to LED actuation frequency of 1 Hz. In vitro quantification of blood calcium and urine pH was performed using fabricated chip scale opto-wetting platforms. The proposed work could be useful in the development of droplet microfluidic chips, where combinatorial mixing can be achieved using an array of LEDs.
KeywordsPhotoisomerization Interfacial tension LED Azobenzene Photoresponsive Contact angle Surface energy
The authors express there sincere thanks to Ministry of Human Resources and Development, Government of India and IIT Hyderabad for their financial support to this project.
Compliance with ethical standards
Conflict of interest
The authors disclose that there is no conflicts of interest to declare.
- Naghii MR, Ebrahimpour Y, Darvishi P (2012) Effect of consumption of fatty acids, calcium, vitamin D and boron with regular physical activity on bone mechanical properties and corresponding metabolic hormones in rat. Indian J Exp Biol 50(3):223–231Google Scholar
- Tandogan B, Ulusu N (2005) Importance of calcium. Perspect Med Sci 35(1):197–201Google Scholar
- Thomas T, Unni HN (2018) LED based opto-wetting platforms for micromixing. In: Proceedings of SPIE 10491, microfluidics, bioMEMS, and medical microsystems XVI, 104910R. https://doi.org/10.1117/12.2290107
- Zak B, Epstein E, Baginski ES (1975) Review of calcium methodologies. Ann Clin Lab Sci 5(3):195–215Google Scholar