On-chip pressure sensing by visualizing PDMS deformation using microbeads

A novel pressure sensing technique based on visualizing Polydimethylsiloxane (PDMS) deformation using microbeads is proposed here for measuring local pressure inside a microfluidic device. By the proposed method, the pressure can be directly “seen” without attaching any wire foils, such as a strain gauge, nor complex fabrication process, such as multilayer design or surface grating. Experimental results are shown and analyzed based on brightness value from captured images of microbeads pattern. The developed sensor is firstly calibrated by a commercial pressure sensor with feedback controlled syringe pump connected externally. According to the experimental results, the proposed sensing method is stable and repeatable in the steady state under dynamic pressure change, and the variation for the same given pressure from time to time is less than 1%. The correlation, R, between the pressure obtained from the proposed method and the reference pressure connected outside is up to 0.9953.