Highly Efficient, Flexible Wireless-Powered Circuit Printed on a Moist, Soft Contact Lens

Contact lens with built-in electronics is a next-generation wearable product with potential applications such as biomedical sensing and wearable displays. However, fabricating a wireless-powered circuit on a moist, soft contact lens, via common dry lithography, makes producing smart contact lenses challenging. Here, electrochemically (EC) printing a wireless-powered circuit onto a moist, soft contact lens is demonstrated. EC printing involves adding a conductive polymer at the interface between a metal contact and a hydrogel-based contact lens, resulting in strong adhesion of the circuit to the lens without losing high power transfer efficiency (50%) from an eyeglass transmitter to the printed receiver lens. The energy transfer characteristics during eye movement are modeled using the Neumann equation and Kirchhoff's voltage law for wireless power transfer. The energy transfer efficiency between the eyeglass transmitter and the printed receiver lens is derived, and illumination of a wireless-powered single light-emitting diode display as a function of eye rotation angle is demonstrated. This work opens the door to integrating more complex circuits at soft contact lens interface to produce smart contact lens with increased functionality.