Detection and Momentum Spectrometry of Single Microparticles by Scanning Force Microscopy Sensors

Abstract

The high sensitivity of a scanning force microscopy lever is exploited for the measurement of the inertial forces exerted on it by impacting gas jets and single particles. Similar to a ballistic pendulum, a lever with an integrated piezoresistive deflection sensor was arranged perpendicular to a microscopic aerosol jet, expanding into the high vacuum of a SEM sample chamber. Piezolever signals were recorded by an external Wheatstone bridge a.c.‐coupled to a differential amplifier. The signal heights obtained by particle‐free gas microjets are proportional to the pressure difference across the closed gas inlet valve. The signals caused by the impact of individual particles of a polydispersive sodium chlorine aerosol show peak amplitudes according to the different particle momenta. Monitoring the resonance frequency of the lever reveals the increasing particle mass load on the target area of the lever.© 1997 John Wiley & Sons, Ltd.