A Multimodal Haptic Feedback Interface with Thin-Film Compliant Mechanism

Multimodal cutaneous haptic interfaces can deliver multiple forms of mechanical stimulation and trigger different mechanoreceptors, enabling richer haptic information and realistic tactile sensations. Such interfaces have broad potential in healthcare, entertainment, and education. Electromagnetic (EM) actuators are particularly attractive for multimodal haptic systems due to their compact size, high controllability, and fast dynamic response. However, existing EM-based multimodal haptic devices struggle to simultaneously achieve large displacement, high output force, and effective constraint of unwanted degrees of freedom. To address this research gap, this paper presents a new thin-film compliant mechanism that exhibits high flexibility in translational motion along the X, Y, and Z axes while maintaining high stiffness against rotations about the X and Y axes. The new design enables the development of an electromagnetic multimodal haptic module capable of delivering indentation, stretch, and vibration stimuli, with the ability to superimpose vibration onto skin stretch. By integrating such two haptic modules into a wearable haptic array and employing a spatiotemporal encoding strategy, four-directional haptic cues can be effectively conveyed on hairy forearm skin, achieving a mean discrimination accuracy of 79.5%. Finally, a vision-guided human-in-the-loop haptic assistance system is implemented to demonstrate feasibility in assisting visually impaired users with daily tasks.