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Ultrafine aerosol particle sizer based on piezoresistive microcantilever resonators with integrated air-flow channel

: Bertke, Maik; Kirsch, Ina; Uhde, Erik; Peiner, Erwin

Fulltext ()

Sensors. Online journal 21 (2021), No.11, Art. 3731, 19 pp.
ISSN: 1424-8220
ISSN: 1424-8239
ISSN: 1424-3210
Journal Article, Electronic Publication
Fraunhofer WKI ()
differential mobility particle sizer; micro electro mechanical system; micro-fluidic channel; piezoresistive micro cantilever; picogram balance; ultrafine particles; carbon aerosol

To monitor airborne nano-sized particles (NPs), a single-chip differential mobility particle sizer (DMPS) based on resonant micro cantilevers in defined micro-fluidic channels (µFCs) is introduced. A size bin of the positive-charged fraction of particles herein is separated from the air stream by aligning their trajectories onto the cantilever under the action of a perpendicular electrostatic field of variable strength. We use previously described µFCs and piezoresistive micro cantilevers (PMCs) of 16 ng mass fabricated using micro electro mechanical system (MEMS) technology, which offer a limit of detection of captured particle mass of 0.26 pg and a minimum detectable particulate mass concentration in air of 0.75 µg/m³. Mobility sizing in 4 bins of a nebulized carbon aerosol NPs is demonstrated based on finite element modelling (FEM) combined with a-priori knowledge of particle charge state. Good agreement of better than 14% of mass concentration is observed in a chamber test for the novel MEMS-DMPS vs. a simultaneously operated standard fast mobility particle sizer (FMPS) as reference instrument. Refreshing of polluted cantilevers is feasible without de-mounting the sensor chip from its package by multiply purging them alternately in acetone steam and clean air.