ELECTRODYNAMIC TRAPPING AND MANIPULATION OF PARTICLE CLOUDS

Apparatus and techniques were developed to electrodynamically trap and manipulate groups of microparticles, The equipment consists of a vibr ating orifice aerosol generator, an inductive particle charger, a plen um chamber, and a double-ring electrodynamic balance. Salt particles ( NaNO3) of controllable and measurable mass and charge were produced an d introduced into the balance In nitrogen at flow rates up to 25 cm(3) /min. Ordered arrays of any number of particles up to 26 were assemble d and manipulated. Methods for compressing the arrays are presented, a nd controlled ejection of single particles from a trapped array is dem onstrated. Particles of opposite polarity were successfully levitated and kept apart, and aggregation of these particles was then induced by changing the electric field. Raman spectra were recorded for multiple salt particles, each having a diameter of 3.5 mu m, by aligning them in a laser beam. The enhanced Raman signal is compared with that from a single particle isolated from the array. From the results, a detecti on Limit of 0.4 pg per particle was estimated. (C) 1997 American Insti tute of Physics.