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substantially greater functionality than an electrical eyeglass. [2,3] Numerous technological advances have been reported for sensors, [4][5][6] displays, [7][8][9][10] and microchips [11] with wired [12][13][14] or wireless power supply systems [15][16][17] to produce smart contact lenses. In 2014, Google demonstrated a proof-of-concept electrical contact lens that assists diabetics by monitoring the glucose level in their tears and transferring related information wirelessly if the glucose concentration remains high after the wearer has eaten a meal. [18] Other research efforts include a readout integrated circuit (IC) chip for wireless communication from a contact lens, [19] a graphene lens coating for electromagnetic interference shielding, [20] and sensors to monitor intraocular pressure [21][22][23] and biochemical changes [24][25][26] for human diagnostics. Separately, Minteer and co-workers developed chemical sensors [27] and biofuel cell systems [28] on contact lenses. However, all such attempts have involved dry lithography on hard/soft contact lenses, or an electronics sandwich structure between two contact lens layers. Most electrical circuit printing techniques are difficult to apply to soft, moist surfaces, but most people prefer wearing moist and oxygen-permeable soft contact lenses.Here, we demonstrate an electrochemical (EC) direct printing of integrated wireless-powered circuits onto a moist, soft contact lens (Figure 1a). EC printing is based on the polymerization of 3,4-ethylenedioxythiophene (EDOT) glue at the interface between the circuit and the hydrogel-based substrate. [29,30] The wireless-powered system consists of an in-parallel connection with a loop antenna inductor (L) and a miniaturized ceramic capacitor (C) for an eyeglass and a contact lens; it is designed for power transfer at a resonant frequency of 13.56 MHz. The frequency is an industrial science medical (ISM) band suitable for receiving power without energy loss when the antenna is positioned near an aqueous medium. This band is also suitable for designing a small loop antenna mounted on the contact lens. We optimized the antenna design and the coupling capacitor for electrical eyeglass and contact lenses to achieve a high power transfer efficiency (η) at an appropriate radiation distance. The system is combined with an AC/DC rectifier circuit and a single light-emitting diode (LED) to demonstrate wireless LED lighting on a pig eye even when the eye is rotated to the maximum angle for human eye rotation (Figure 1b). Contact lens with built-in electronics is a next-generation wearable productwith 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 ...

Smart contact lenses—contact lenses with built‐in electronics—are a next‐generation wearable product with capabilities beyond simple vision correction. In article number https://doi.org/10.1002/admt.201800671, Taiki Takamatsu, Takeo Miyake, and co‐workers develop a highly efficient, flexible wireless‐powered circuit based on metallic loop antenna and then provide a new way to mount its circuit onto a moist, soft contact lens with electrochemical bonding.

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