Counting of water-in-oil droplets for targeted drug delivery systems using capacitive sensing technique

Droplet-based microfluidics has drawn attention of scientists due to its broad applicability in medical devices for targeted drug delivery. The use of microfluidic droplets has several advantages, among which reduction of reagents volumes is one of the most important. We propose a low-cost sensor system based on capacitive sensing technique for monitoring of water droplets that can be incorporated in existing lab-on-chip devices. The sensing unit is composed of gold interdigital electrodes (IDEs) patterned on top of a glass substrate. There is an insulation layer to avoid cross contamination of fluids and a PDMS cover to form the microchannel. The sensor was tested for detection of water-in-oil droplets and main experimental results show that presence of water droplets will induce an increase in measured voltage due to higher relative permittivity of water when compared to oil. A LABVIEW interface allows real time visualization of signals and counting of droplets.