Fully Bioabsorbable Capacitor as an Energy Storage Unit for Implantable Medical Electronics

Abstract

Implantable medical electronic devices are usually powered by batteries or capacitors, which have to be removed from the body after completing their function due to their non‐biodegradable property. Here, a fully bioabsorbable capacitor (BC) is developed for life‐time implantation. The BC has a symmetrical layer‐by‐layer structure, including polylactic acid (PLA) supporting substrate, PLA nanopillar arrays, self‐assembled zinc oxide nanoporous layer, and polyvinyl alcohol/phosphate buffer solution (PVA/PBS) hydrogel. The as‐fabricated BC can not only work normally in air but also in a liquid environment, including PBS and the animal body. Long‐term normal work time is achieved to 30 days in PBS and 50 days in Sprague–Dawley (SD) rats. The work time of BC in the liquid environment is tunable from days to weeks by adopting different encapsulations along BC edges. Capacitance retention of 70% is achieved after 3000 cycles. Three BCs in series can light up 15 green light‐emitting diodes (LEDs) in vivo. Additionally, after completing its mission, the BC can be fully degraded in vivo and reabsorbed by a SD rat. Considering its performance, the developed BC has a great potential as a fully bioabsorbable power source for transient electronics and implantable medical devices.

Materials Strategies and Device Architectures of Emerging Power Supply Devices for Implantable Bioelectronics

“…Although their power densities are generally lower compared to those of battery systems, supercapacitors can be integrated with other energy harvesting systems and provide rapid energy storage. By incorporating various materials in the thin film formats, including metals, oxides, silicon, carbon materials, and organic polymers, supercapacitors can be reformulated into novel, flexible, stretchable, and biodegradable (or edible) systems that can better adapt to the human body . Chae et al implanted two biocompatible hybrid electrodes fabricated by MnO 2 and carbon into the subcutaneous layer of rat's skin as shown in Figure a, demonstrating a stable supercapacitor performance (0.2–1 V at 2 mA) for 5000 cycles …”

“…Biodegradable and edible supercapacitors have also been proposed . As shown in Figure e, Lee et al reported the first biodegradable supercapacitors using water‐soluble metallic electrodes and an agarose electrolyte.…”

The recent advances in self‐powered medical information sensors

“…For some specific application scenarios, a tunable lifetime of the sensor is expected. Biodegradable materials were selected for TENG or PENG fabrication . The inherent biodegradability or artificially modified biodegradable property were usually obtained for component materials.…”

Sunlight‐Triggerable Transient Energy Harvester and Sensors Based on Triboelectric Nanogenerator Using Acid‐Sensitive Poly(phthalaldehyde)

“…Among them, cyclic poly(phthalaldehyde) (PPHA) with a low ceiling temperature (T c = −43 °C) has received broad interest due to its promising mechanical properties, ease of synthesis, and fast depolymerization rates. To our best knowledge, most of existing reports on transient power sources are about energy storage devices, [16][17][18] and only transient energy harvesters whose degradation requires aqueous solution have been demonstrated. [13] Tang et al reported a programmable payload release system from PPHA-based microcapsules, whose release rates could be controlled by the composition and concentration of the salt/acidic methanol solution.…”