Integratable capacitive bubble counter for lab-on-chip devices

Recently, microfluidic devices for two-phase flows detection have been given significant attention. This is due to their commercial value and wide range of applications, from medical devices to heat exchangers and integration in lab-on-chip devices. Microbubbles are of great importance on medical field and for that we designed a capacitive bubble counter for monitoring. Details of design and modeling of the capacitive bubble counter have been presented. The bubble counter comprises of planar interdigital electrodes (IDEs) patterned on the top of a glass substrate. The IDEs are covered by a thin PTFE insulation layer. The glass substrate bonded with a PDMS cap forms the microchannel where the liquid-bubble two-phase flow passes through. Finite element method (FEM) analysis confirms the operation principle of the counter, showing that the resultant capacitance of the counter decreases whenever an air bubble is inside the microchannel. Besides, the influences of geometrical characteristics of the IDEs upon the capacitance have been thoroughly investigated.