Fig. 3: Concept of the micro-epidermal actuator array.

a Illustration of a horizontal array attached to a patient with aural atresia. Vibrational signals are generated by each actuator, constructively interfering with the bone to produce a stronger signal. The cochlea picks up the combined vibrations and transmits the auditory signal to the brain. b Schematic of a horizontal and stacked array in flexible substrates. c A single-phase hearing aid device with a stacked array. d Comparison of PZT and arrays on a human skull at 600 Hz. Arrays distribute the vibrations across a larger surface area. e Minimum voltage required for the MEA/array to produce an audible vibration for the subject. The error bars represent the standard deviation from measuring 10 subjects. (Panels taken from Figs. 1, 2, and 4 of the original paper).