A Self-running Standing Wave-type Bidirectional Slider for the Ultrasonically Levitated Thin Linear Stage

A slider for a self-running standing wave-type, ultrasonically levitated, thin linear stage is discussed. The slider can be levitated and moved using acoustic radiation force and acoustic streaming. The slider has a simple configuration and consists of an aluminum vibrating plate and a piezoelectric zirconate titanate (PZT) element. The large asymmetric vibration distribution for the high thrust and levitation performance was obtained by adjusting the configuration determined by finite elemental analysis (FEA). As a preliminary step, the computed results of the sound pressure distribution in the 1-mm air gap by FEA was com pared with experimental results obtained using a fiber optic probe. The direction of the total driving force for the acoustic streaming in the small air gap was estimated by the sound pressure distribution calculated by FEA, and it was found that the direction of the acoustic streaming could be altered by controlling the vibration mode of the slider. The flexural standing wave could be generated along the vibrating plate near the frequencies predicted based on the FEA results. The slider could be levitated by the acoustic radiation force radiated from its own vibrating plate at several frequencies. The slider could be moved in the negative and positive directions at 68 kHz and 69 kHz, which correspond to the results computed by FEA, with the asymmetric vibration distribution of the slider's vibrating plate. Larger thrust could be obtained with the smaller levitation distance, and the maximum thrust was 19 mN.