Viscous Damping in a Microfluidic Load Sensor

A typical microfluidic load sensor consists of an electrolyte-filled microfluidic channel capped by a flexible plate. Under a load applied on the top flexible plate, the fluid within the microchannel is squeezed by the deflected plate, resulting in an opposite hydrodynamic pressure force on the plate. Thus, the electrolyte within the microchannel can induce a significant viscous damping effect on the dynamic response of such a microfluidic load sensor, whose output signal is proportional to the deformation of the flexible plate. Considering the coupling between the deformation of the flexible plate and the hydrodynamic fluid pressure, a mathematical model for analyzing the dynamics and viscous damping of the sensor is developed. Dynamic characteristics of the plate and the equivalent viscous damping coefficient as the functions of the load amplitude and the frequency as well as the sensor's geometric parameters are investigated. The obtained results qualitatively agree with the experimental observations in the literature. The results show that the load sensor is overdamped, and the viscous damping has significant influences on the dynamic response of the flexible plate in the microfluidic load sensor. The microfluidic channel depth has more significant effects on the plate deformation than the plate's width and thickness.