Manipulation of Powder with Surface Acoustic Wave Actuator to Control Standing and Traveling Modes

In this study, we fabricated a new surface acoustic wave (SAW) actuator that can control the SAW mode of a powder-manipulation area between an interdigital transducer (IDT) (for generating the SAW) and an elastic-sheet (chloroprene rubber) pressurizer. In particular, the propagation surface near the ends of the substrate, at which the SAW is reflected, is pressurized with elastic bodies to suppress the reflected wave. We used laser Doppler vibrometry with the fabricated SAW actuator to investigate the change in SAW mode from standing to traveling due to elastic-sheet pressurization. The results of the investigation revealed two key points: (i) the amplitude of the reflected wave could be suppressed by about 90% by elastic-sheet pressurization and (ii) the SAW could be switched between the standing, traveling, and intermediate modes. We then investigated the behavior of a powder (100-mu m-diameter SiO2) using the SAW actuator. We found that the powder could be dissipated by the SAW in the standing mode and then transported to the IDT side by utilizing the SAW in the traveling mode. It was also shown that a SAW in the intermediate mode between the standing and traveling modes (namely, the amplitude of the reflected wave is about one-third that of the incident wave) can be used to transport the powder to the IDT side while dissipating it.