Filling volume sensor for microfluidic applications based on thermic transient effect and standard PCB technology

A liquid volume sensor has been developed on standard printed circuit board (PCB) technology, based on thermic transient effect. The sensor layer is built on 200 μm thick FR4 (Flame Retardant 4) substrate with 35 μm Cu coating, and the other walls of the fluidic chamber are made of Fullcure 720 rapid prototyping (RPT) photopolymer compound. The measurement process is based on a heated, meander-shaped Cu structure and it is controlled automatically by a microcontroller-based digital control unit. The filling volume is calculated from the gradient of the output voltage of the sensor and the applied heating power. A simple measurement system has been built to observe and to verify the preliminary thermic and electrical simulations of the sensor.