International Business Machines Corporation
MEMS optical liquid level sensor

Abstract:

Microfluidic chips incorporating liquid level sensors for precise sensing of liquid levels in microfluidic system structures, e.g., channels, cavities or reservoirs without moving parts. The microfluidic system uses liquid level photosensors and use optical properties to measure liquid volumes. A light coupling emitter or waveguide transmits the light toward the fluid channel at a critical angle. Multiple light coupling emitters and photosensor array can detect light for a variety of scenarios (based on fluid refraction index) and exploit the phenomenon of critical angles to measure exact angles of reflection/refraction. The waveguide coupler(s) and photosensors are manufactured at the microscale, and use both reflected light and refracted light as monitor signals. A feedback control system (e.g., compensating for rate and tolerance drift) is devised using signals generated by the sensors upon detecting reflected or refracted sensed light for increased accuracy of detecting precise amounts of fluid volumes being dispensed.