Ferrofluid electromagnetic actuators for high-fidelity haptic feedback

Engineering high-fidelity haptic actuators is challenging due to the impressive tactile sensing characteristics of human skin, which possesses a wide frequency bandwidth, high spatial and temporal resolution, and large dynamic range. These attributes cannot be matched by existing haptic feedback technologies. Efficient, compact electromagnetic haptic actuators are needed in many emerging haptic systems, but their bandwidth and dynamic range are fundamentally constrained by heat transfer effects that become extremely limiting as device dimensions are decreased. Here, we present a compact actuator for delivering high-fidelity haptic feedback via an electromagnetic assembly comprising a magnetically-driven fabric-reinforced elastic membrane coupled to a ferrofluid encapsulated magnetic circuit. Using theoretical modeling, simulations, and experiments, we show how the mechanical design, magnetic circuit, and thermal design of this fingertip-sized actuator enable it to deliver sustained forces or indentations, wide-bandwidth vibrations, sustained forces of 3 Newtons, transient forces exceeding 13 Newtons. These actuators can be leveraged to supply many emerging systems and products with high fidelity haptic feedback.