Wall loss reduction technique using an electrodynamic disturbance for airborne particle processing chip applications

Wall loss is a major cause of deteriorating performance and reliability in air-based miniaturized analytical devices and it can cause unexpected changes in structures and operational conditions. Therefore, there is a great demand for the reduction of the wall loss on airborne particle processing chips. This paper demonstrates a wall loss reduction technique using an electrodynamic disturbance. The proposed technique is applied to a serpentine microchannel for a feasibility test, and then it is applied to a virtual impactor, which is an inertial airborne particle classifier. An electrodynamic disturbance is generated by applying ac electric potentials to an interdigitated electrode pair integrated at the bottom of the microchannel. In the serpentine microchannel, the application of electric potentials from 0 to 3 kV at 1 kHz caused the wall loss to decrease exponentially as a function of the aerodynamic diameter. When the electric potential was 3 kV, the wall loss decreased by 17.2 plus or minus 1.8% for particles with a 0.96 mu m diameter. In the virtual impactor, the wall loss curve at 1 kV and 1 kHz had an estimated maximum reduction of 11.6% compared to the wall loss curve at 0 V. Furthermore, the collection efficiency curves approached the ideal cut-off curve as the applied electric potential was increased from 0 to 1 kV.