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

Abstract

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 ...

Electronic Contact Lens: A Platform for Wireless Health Monitoring Applications

“…More recently, electronic contact lenses have been considered as an effective noninvasive platform for detecting and diagnosing vital human signs, particularly for the detection of glucose levels in diabetic patients, as well as glaucoma . Thanks to the integration of biotechnology, information technology, and microelectronics on the contact lens platform, various biosensors and electrochemical sensors have been developed on lenses for the detection of these biomarkers . They have also been considered for protecting eyes from electromagnetic waves and dehydration, thereby reducing the risk of cataracts .…”

All-printed stretchable corneal sensor on soft contact lenses for noninvasive and painless ocular electrodiagnosis

“…Figure 1e shows the surface topology of the corneal sensor with (red line) and without (blue line) a PEDOT layer, of which the electrochemical processing time was fixed at 4 min. The results indicate that the peak heights remained <10 µm, while the formation of the PEDOT layer occurred predominantly at the edge of the corneal sensor due to uneven current distribution across the round surface 30 . Consequently, a gradual taper angle of ≤30° was created at the edge of the PEDOT layer, offering enhanced conformal contact to the corneal surface.…”

Advances and current challenges in non‐invasive wearable sensors and wearable biosensors—A mini‐review

“…In order to succeed the ocular WBS uses, it will be necessary not to interfere with the transparency and flexibility conditions of the contact lenses and nor to affect the optical necessities (Kim, Kukjoo, et al, 2019; Wei et al, 2019). The electronics compounds incorporated must be capable of having their mechanical, chemical and electrical properties for a highly sensitive, selective and wireless response, which needs to be connected in real time with the user by a computer or a smartphone (Takamatsu et al, 2019).…”

“…Journal compilation © 2008 Acta Ophthalmol). (j) The smart contact lens for energy storage and LED lighting on the lens when AC voltage is applied to the 13.56 MHz eyeglass transmitter (Takamatsu et al, 2019) (reproduced under the terms licence © 2019 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim). (k) WBS in the form of contact lens in mechanical deformation, and the device in free movement, placed in the eye (Kouhani et al, 2019) (reproduced under the terms of licence Copyright © 2001, the authors, Royal Society of Chemistry).…”