Optical/Thermal Droplet Levitation and Transport for Lab-On-A-Chip

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

CBET-0828820 Neitzel This research seeks to apply knowledge gained through previous federal support to lab-on-a-chip processing (Bousse, et al. 2000, Whitesides & Stroock 2001). These miniaturized microfluidics devices transport minute liquid samples and reagents from point to point for testing purposes. Typically, such a microfluidics device consists of an array of micro-machined channels or capillaries through which the liquids are forced in a variety of fashions (Stone, et al. 2004). In many 'pumping' strategies, a large pressure difference is created between the ends of an isolated droplet to simply push the droplet through the capillary inversely proportional the capillary radius to the fourth power. The intellectual merits of this work centers on developing and using a novel optical/thermal strategy for droplet transport and mixing using 'permanent nonwetting', using thermocapillary convection to keep liquid samples from contacting solid surfaces, although they are in close proximity. These levitated droplets translate above a solid surface with very low friction, enabling the movement of liquid from point to point with little force, and in shorter time, improving device throughput. Transport of aqueous droplets (of greatest interest for bio-chip applications) will be facilitated by encapsulating the aqueous droplet within immiscible oil. The vigorous internal convection driven by thermocapillarity promotes merging of encapsulated samples as well as mixing of the contents, otherwise difficult with most low-Reynolds-number schemes. The proposed encapsulated-droplet-transport mechanism will also inhibit sample-to-sample contamination. The broader impacts of this research include benefits to the medical-device industry, among others. As part of this research, a partnership has been established with the Fernbank Science Center, a division of the Dekalb County (GA) Board of Education, to develop an ensemble of experiments to stimulate interest in droplet dynamics and fluid physics in secondary school students. These experiments, more than simple demonstrations, require students to collect and analyze data as part of the exercise. The PI will endeavor to promote this exciting research and stimulate minority students to consider graduate study in engineering by giving lectures to undergraduate students in schools of the Atlanta University Center (Morehouse & Spellman Colleges; Clark-Atlanta University).