Surface Cleaning of SAW-Based Microparticle Sensors Integrated in a Cascade Impactor Using SAW-Induced Droplet Displacement.

A cascade impactor equipped with microparticle surface acoustic wave sensors along with a surface cleaning system is an innovative system developed by our team to measure particles and monitor air quality. The system has been proven to function properly under various particle concentrations. Nevertheless, long exposure times and heavily polluted media impose a limitation on cascade impactors, known as surface saturation. This problem affects the sensitivity of our sensors, which tends to degrade with particles fouling the surface. To overcome this issue, a surface cleaning system that uses a Rayleigh wave-actuated water droplet has been implemented and tested. Rayleigh waves were generated on an innovative SAW chip, thus exciting the droplet using Radio-Frequency power. NaCl solutions and SiC particles were considered. The optimal droplet size was determined along with the required Radio-Frequency power. Experiments showed that the SAW-driven droplet successfully displaced the collected particles outside of the sensing zone, irrespective of their nature, without affecting the sensor's performance. The results found in this study provide further improvements to our particle measuring system, advancing it towards an autonomous self-regenerating prototype.