Fabrication of Shearing‐Motion‐Type Tactile Display Mechanism Using SMA Thick‐Film Actuators and Coil Springs Array

Abstract A shearing‐motion‐type microelectromechanical system (MEMS) tactile display mechanism was fabricated to provide a shear vibration stimulus to the fingertip. It consisted of shrinking shape memory alloy (SMA) thick‐film actuators and a supporting coil spring array. The SMA actuator array was designed and fabricated using a flash‐evaporated SMA film (10 μm thick) on a mirror‐polished Cu substrate. The coil spring was successfully arrayed on a glass substrate with an SU‐8 circular array pattern. The glass substrate with the coils was bonded to the SMA substrate to complete the shearing‐motion mechanism. During the bonding process, the SMA actuators were initially elongated by the coil springs. The generated amplitude and force of the fabricated mechanism were characterized when the SMA actuator was heated by applying a pulsed current to be shrank by the shape recovery effect. The fabricated shearing‐motion mechanism successfully generated large amplitude of 41 μm (around 80 μm in reciprocal motion) and force of 22 mN at a driving frequency of 1 Hz. At 20 Hz, an amplitude of 23 μm and force of 10 mN were obtained even though they were reduced owing to the low thermal response. At both driving frequencies, the obtained amplitudes and forces seems to be sufficient for tactile stimulation to finger skin. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.