Development of liquid pumping devices using vibrating microchannel walls

In this paper, we propose innovative valveless pumping devices for microfluidic systems. The liquid in the microchannel was transported by generating a traveling wave on the channel wall, which was composed of a piezoelectric Pb(Zr,Ti)O3 (PZT) thin film actuator array. The PZT thin films were deposited on the silicon-on-insulator (SOI) substrates where microchannels, 200 and 500 μm wide, were fabricated by deep reactive ion etching (DRIE). The displacement profiles and frequency response of the vibrating wall were measured using a laser Doppler vibrometer. The maximum displacements of the 200 and 500 μm wide empty channels at 10 Vpp were about 62 and 229 nm, respectively. Minor displacement reductions were observed when the channel was filled with liquid, although the resonant frequencies dropped remarkably. On generating a traveling wave on the channel wall, clear liquid flow could be induced with a mean flow velocity of about 118 and 172 μm/s for the 200 and 500 μm wide channels, respectively.