Particulate Matter Sensor Based on Two-Stage Cascade Virtual Impactors and Thermophoretic Microheaters

A particulate matter (PM) sensor that simultaneously measures the concentrations of PM
2.5
and PM
1.0
is reported in this study. Two serially connected virtual impactors (VIs) separate aerosol particles according to their sizes, which are subsequently collected on the surface of the gravimetric sensor through thermophoresis. The fabricated device achieved a mass sensitivity of 11 Hz/min per μg∙m
^-3
and 10 Hz/min per μg∙m
^-3
for PM
2.5
and PM
1.0
, respectively, which is the highest among the gravimetric PM sensors reported to date. This result is attributed to the precise fluid-dynamic design of the VIs and the development of efficient microheaters that can provide localized heat and corresponding forces to the aerosol particles.