Horizontal chip-scale cascade impactor with integrated resonant mass balances

This work presents design and fabrication of a chip-scale horizontal cascade aerosol impactor capable of collection, size separation and real-time concentration measurement of airborne particles. The presented microsystem consists of two attached micromachined silicon chips: 1. the main SOI chip, where the resonant mass balances, micro-nozzles, and air feedthroughs are formed, and 2. a silicon sealing cap with air-path cavities and feedthroughs for electrical and vacuum connections. To our knowledge, this is the first demonstration of a fully micromachined cascade impactor. During laboratory tests on a two stage prototype, particle concentrations for two particle cut-off sizes of 140 nm and 40 nm were successfully measured.