Open-Chip Droplet Splitting in Electrowetting

Sagar, N and Bansal, S and Sen, P (2022) Open-Chip Droplet Splitting in Electrowetting. In: Advanced Materials Interfaces .

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Abstract

Electrowetting-on-dielectric (EWOD) has emerged as a powerful technique to perform on-chip droplet operations like transportation, dispensing, splitting, and mixing in sandwiched droplets. In contrast, open-chip droplet manipulation using electrowetting enables micro-total-analysis systems with multiple sensor integration and re-routing capabilities. Droplet splitting has been the bottleneck in developing open-chip platforms. Droplet splitting on an open-chip platform using electrowetting-on-dielectric is presented. An energy-based simulation model has been developed. It shows that splitting a sessile water droplet is impossible on an open-chip configuration because of the low pad contact angle requirement. Low contact angles cannot be achieved due to contact angle saturation in electrowetting. It is experimentally shown that splitting is possible if the droplet is engulfed in an oil shell (i.e., in compound droplets). The planar electrode configurations and regime of electrowetting numbers for which splitting can be achieved are identified. It is observed that larger gaps and higher electrowetting numbers favor symmetrical splitting because the electrostatic force driving the actuation is significantly higher than the retarding interfacial forces. Conversely, asymmetrical splitting has been obtained when the actuation force is barely sufficient. Further the splitting of surfactant-loaded single-phase sessile droplets is demonstrated and a preferential surface charging phenomenon is explained.

Item Type:	Journal Article
Publication:	Advanced Materials Interfaces
Publisher:	John Wiley and Sons Inc
Additional Information:	The copyright for this article belongs to John Wiley and Sons Inc.
Keywords:	Drops; Wetting, Compound droplet; Droplet manipulation; Electro-wetting on dielectrics; Electrowetting; Electrowetting on dielectrics; Micro total analysis systems; Multiple sensors; On chips; Open-chip platform; Splittings, Contact angle
Department/Centre:	Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering
Date Deposited:	05 Oct 2022 06:12
Last Modified:	05 Oct 2022 06:12
URI:	https://eprints.iisc.ac.in/id/eprint/77040

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