Exploitation of an integrated microheater on QCM sensor in particulate matter measurements

Most QCM-based devices devoted to PM measurement use substrates of various kinds to collect and retain particles. The novelty of this work is the possibility to use an integrated microheater actuator to change the substrate collecting features during the particulate adsorption. In fact, this paper presents preliminary results about the exploitation of a HQCM (Heated Quartz Crystal Microbalance) in particulate matter (PM) measurements. HQCM is a 10 MHz quartz crystal microbalance with a microheater and a resistive temperature detector (RTD) implemented on its surface. The effects of the sensor surface temperature (T1 = 20 °C and T2 = 80 °C) on the PM detection have been studied by a suitable particulate measurement system, where the HQCM coated by grease, worked both as impaction plate and mass sensor. HQCM was tested providing to it a sequence of impulses of microsphere of Cerium (IV) oxide dispersed in synthetic air (715 μg/m3 of PM2.5 and 43 μg/m3 of PM1, lasting 1 min) and recording the consequent resonant frequency shift. The results have shown that the HQCM was able to detect PM both at T = 20 °C and at 80° C. Grease coated HQCM exhibited a good frequency stability at T = 80 °C (± 5 Hz) with a negligible grease mass loss during several heating cycles. Furthermore, the results have shown that the surface temperature changes the collection capacity. In particular at higher temperature (80 °C) the frequency change was 2.5 times greater than that at lower temperature (20 °C).