Capacitive Sensor for Contact Angle Estimation of Droplet on Microfluidic Chip

This paper proposes a capacitive-sensor-based system to estimate contact angle of droplet on IC chip. To integrate contact angle measurement system into microfluidic system, our research goal is to realize fully electrical measurement by standard CMOS compatible devices. We use two types of capacitors, one is edge-detecting capacitor, and another is contact angle estimating capacitor. Electromagnetic simulations show that the proposed method can estimate the contact angle even though the relative permittivity of the liquid is varied from 10 to 100.