Fig. 3. Haptic feedback performances.
(A) Photograph of a flexible actuator and a 10-cent Hong Kong dollar coin. (B) The principle of haptic feedback by the flexible actuator. The oscillation of the magnet induced by the alternating electric field exerts mechanical feedback on the skin. (C) Different PDMS films with a 0.5-mm-thick magnet. (D) Relationship between PDMS thickness and spin-coating speed. (E) Resonant frequencies of the actuators with different thick PDMS films. (F) Amplitude at different actuation frequencies for the flexible actuator with a resonant frequency at 195 Hz. (G) Values of the vibration amplitude with time for the actuator with 345-μm-thick PDMS film. (H) Relationship between the actuator’s vibration amplitude and the actuation sinewave AC current. (I) Optical images of troughs and peaks state for the vibrating actuator recorded using a high-speed camera. (J) FEA results of the actuator’s vibration in the downward, leveled, and upward direction. (K) FEA results of a flexible actuator and a rigid actuator applied on the skin. The flexible actuator presents low stress to the skin. (L) The normalized contact stress (σN) distributions at the interface between the skin and actuator applied on (top) undeformed skin and (bottom) R = 28 mm, respectively, as shown in movie S3. (M) Photographs of the self-sensing and haptic-reproducing e-skin on different body parts. (N) Accuracy summary of the haptic feedback test by four representative static patterns and four dynamic patterns applied to five typical parts of the body.