We present a device for controlled injection of a variety of materials in powder form. The
system implements four independent feeder units, arranged to share a single vertical drop
tube. Each unit consists of a 80 ml reservoir, coupled to a horizontal linear trough, where a
layer of powder is advanced by piezo-electric agitation at a speed proportional to the
applied voltage, until it falls into a drop tube. The dropper has been tested with a number of
impurities of low (B, BN, C), intermediate (Si, SiC), and high Z (Sn) and a variety of …