Droplet Sorter using a Cantilever Actuated by Electro-Conjugate Fluid Micropumps

Abstract

Sorting droplet (cells) process is critically important in some biological and medical applications, e.g., disease diagnosis and cellular behavior investigation. The previously reported methods typically exert environmental stress (high temperature, magnetic field, contamination from other fluids, etc.) on the droplets. This can cause a reduction of sample viability after the sorting process. We will present a microfluidic sorter that has a cantilever acting as a diverter. The cantilever is actuated by two flexible membranes powered by on-chip ECF (Electro-conjugate Fluid) micropumps. ECF is a type of functional and dielectric oil, which can generate a fluid flow (called ECF jet) when we apply a high DC voltage to the electrodes (anode & cathode). The vertically flexible membranes are made of silicone elastomers. In the device, a T-junction droplet generator is used to provide W/O (water in oil) droplets. The fabrication of the sorter is based on the photolithographic patterning of thick negative tone photoresists (KMPR and SU-8) and the normal electroforming. We successfully fabricated the ECF sorter.