Non-invasive nano-flow sensor for application in micro-fluidic systems

Abstract

A novel, non-invasive fluid flow sensor principle is proposed, which enables measuring flow rates in the nano- to microliter per minute range. In the chosen sensor set-up, the liquid flows from an open reservoir, a typical design in micro-fluidic systems. The sensor is based on a two to one optical fiber coupler, which illuminates the liquid surface in the reservoir and collects the light reflected from the surface. The intensity of the captured light is proportional to the distance between the optical probe and the liquid surface. As a consequence, the liquid flow can be derived in quasi real time (<0.4 s in the case of 0.3 nl/s) from the decline of the liquid surface, an excellent basis for adaptive flow control in micro-fluidics. The sensor can be easily adapted to any kind of micro-fluidic system as long as the liquid flows from an open reservoir. Moreover, there is no need for complex integrated sensor fabrication under clean room conditions. The proposed flow sensor has potentially a higher sensitivity and a wider dynamic range than the previously existing solutions.