Thin-film bidirectional transducers for haptic wearables

Abstract

We have designed, fabricated, and characterized a flexible electrostatic transducer (FET) for potential use as a wearable haptic actuator. This transducer both generates motion through the vibration of a curved electrode and measures the displacement of the same curved electrode to act as a displacement sensor. The transducer was analyzed through theory, simulation, and experiment to determine its displacement and sensing performance. It was found that a transducer with a footprint of 25 mm × 12.5 mm was able to generate displacements between 0.1 mm and 3.2 mm of displacement when operated at voltages between 25 V and 150 V. It was also capable of audible actuation at frequencies anywhere between 0.01 Hz and 10 kHz, including at target frequencies relevant to haptic communication. The transducer was able to sense changes to its shape through a change of capacitance, with a signal change of around 10% during maximum displacement. This sensing allows for both bidirectional communication and automatic displacement control through self-sensing. Simulation and theoretical results provide insight into the mechanism of actuation for the actuation and sensing systems, including predictions of displacement for a given voltage. User studies were also conducted, where it was found that the transducer generated perceivable and comfortable vibrations at both 26 Hz and 260 Hz, with 260 Hz being perceivable at lower amplitudes. The present work describes and characterizes a promising transducer for haptic communication.