A CMOS Optical feedback control for high-speed DEP based microfluidic actuation

We report on the development of a feedback control system that utilizes a custom CMOS optical sensor, to facilitate controlled and precise dispensing and transport of nano-liter liquid sample droplets by leveraging liquid-DEP (L-DEP) and droplet-DEP (D-DEP) actuation schemes. Operationally, L-DEP and D-DEP typically require application of AC voltages across a pair of coplanar microelectrodes for a very short duration of time (~50 ms). The feedback control scheme, utilized to control the droplet dispensing and transport, relies on a CMOS optical sensor to detect perturbations in the light intensity induced by the liquid finger or spherical droplet, as they traverse over the optical sensor and interact with the incident illumination. A fully functional prototype was developed and its operation successfully tested using example L-DEP and D-DEP structures.