Eye Tear Activated Mg‐Air Battery Driven by Natural Eye Blinking for Smart Contact Lenses

Abstract

Smart, adaptive contact lenses (SCLs) are amongst the most anticipated, next-generation, standalone medical devices. SCLs require the integration of thin microelectronic components, tunable lenses, and micro-power sources onto a common non-planar substrate. Here, we report a miniaturized, sliding metalair electrochemical micro-battery driven by natural eye blinking motion that can be integrated with an SCL platform as a source of electrical energy. The metal-air battery (3⋅8 mm 2 ) consists of a Mg anode and a Pt cathode. The electrolyte of the battery is the eye-tear liquid and is introduced to the battery structure during the natural eye-blinking cycle, which activates the battery. The open-circuit voltage across the eyetear activated metal-air battery (ETMAB) was measured to be 2.2 V and the maximum speci c capacity of 3561 mA h g −1 was obtained at a discharge current density of 5 mA•cm −2 . Impedance matching analysis exhibits the maximum generated power density of 1.3 mW•cm −2 at the load of 740 Ω.

Biofluid‐Activated Biofuel Cells, Batteries, and Supercapacitors: A Comprehensive Review

“…in which an Mg‐Air cell was activated with a sliding electrolyte (here tears) periodically dragged on top of the electrodes during the natural eye‐blinking motion. [ 128 ] Pt was selected as the cathode material due to its high power density of 70 µW cm –2 and Mg was selected as the anode material. When the eye was closed, tears contacted with anode and cathode and provided a closed circuit to activate the cell.…”

“…The CuHCFe cathode exhibited an oxidation capacity of 176.6 μAh between 0.6 and 1.1 V, and the FeHCFe anode exhibited a reduction capacity of 181.8 μAh between 0.1 and 0.6 V. The fabricated cell offered a discharge capacity of 155.4 μAh at 100 μA with cutoff voltages of 0.2 and 0.9 V and successfully powered a low-power static random-access memory designed to operate in the voltage range of 0.26 to 1.2 V. Another approach that could be incorporated into a smart contact lens was described by Pourshaban et al in which an Mg-Air cell was activated with a sliding electrolyte (here tears) periodically dragged on top of the electrodes during the natural eye-blinking motion. [128] Pt was selected as the cathode material due to its high power density of 70 μW cm -2 and Mg was selected as the anode material. When the eye was closed, tears contacted with anode and cathode and provided a closed circuit to activate the cell.…”

The Future of Vision: A Review of Electronic Contact Lenses Technology

“…Very recent study showcased a small metal-air microbattery that was powered by the movement of natural blinking and could be integrated with smart CL technology. 45 The battery was made up of a magnesium anode and a platinum cathode on an insulating substrate, with the electrolyte being a thin film of eyetear fluid that was spread over the electrodes during blinking. The battery produced an open-circuit voltage of 2.2 V when tested with an eye emulator.…”

“…These methods include but are not limited to external powering like wired connections and wireless power transmission (WPT), in vivo powering like biofuel cells, and flexible batteries, supercapacitor, and hybrid approaches. Very recent study showcased a small metal-air microbattery that was powered by the movement of natural blinking and could be integrated with smart CL technology . The battery was made up of a magnesium anode and a platinum cathode on an insulating substrate, with the electrolyte being a thin film of eye-tear fluid that was spread over the electrodes during blinking.…”

Ultralow Power On-the-Eye Vergence and Distance Sensing Through Differential Magnetometry

“…Smart contacts require several subsystems for their realization. Some key components are varifocal lenses [12]- [14], various types of power sources like wireless power transfer [15]- [18], metal-air batteries [19]- [21], solar cells [22]- [25] and other bio-fluid based energy harvesters [26]- [28], object distance sensors [29]- [31], electronic components and flexible interconnects between these subsystems [32] and soft packaging to encapsulate these components [33], [34]. All these subsystems must conform to the small form factor of a thin shell in contact with the eye and operate with very little electrical power consumption as possible as energy storage is, in general proportional to the system volume, and for this application, the thickness is in the order of 1 mm or less.…”