Power Source For Implantable Devices Research Articles

Flexible and stretchable high performance enzymatic biofuel cells implantable in tube-type artificial blood vessel kit

Enzymatic biofuel cells (EBFCs) are emerged as promising power sources for implantable devices, offering excellent form factor and performance. For these applications, EBFCs require customer tailored structure and more than 10 μW power. In this study, flexible and stretchable EBFCs are suggested, assessing their performance using tube-type artificial blood vessel (TABV) cell kit with sheep blood fuel. To fabricate the EBFCs, buckypaper (BP) is molded to polydimethylsiloxane (PDMS) to fabricate BP@PDMS electrode that shows excellent strain rate (95 %) and durability (1500 cycles) in tensile and fatigue tests. Additionally, electrochemical evaluations are implemented to measure the performance of anode and cathode fabricated with BP@PDMS. In anode including 1,10-phenanthroline-5,6-dione and glucose dehydrogenase, maximum reactivity of glucose oxidation is 1.05 mA/cm2, while in cathode including bilirubin oxidase, that of oxygen reduction is 0.61 mA/cm2. Regarding flexibility, anode and cathode are little affected by current density irrespective of bending angle, proving that the fabricated anode and cathode have good flexibility. To emulate the behavior of EBFCs in actual blood vessel, EBFCs are implanted in TABV cell kit, fueling sheep blood. Observed open circuit voltage of 0.59 V and maximum power of 26 μW reveals that fabricated EBFCs have superior potential to be considered as power sources for implantable devices.

High-Energy-Density Sputtered Iridium Oxide Micro-Supercapacitors Operating in Physiological Electrolytes

Traditional power sources for implantable devices, such as packaged internal batteries, suffer from bulkiness, limited cycle lifetime, and patient discomfort due to the need for periodic replacement surgery. Supercapacitors that directly utilize bodily fluids as electrolytes may serve as alternative power sources that are compact, durable, and patient-friendly. In this work, we present high-performance micro-supercapacitors that operate stably in physiological electrolytes for their potential as implantable miniature power sources. Sputtered iridium oxide films (SIROFs) produced using water-oxygen plasmas are employed as micro-supercapacitor electrodes and characterized in phosphate-buffered saline (PBS) and an inorganic model of interstitial fluid (model-ISF). The SIROF micro-supercapacitors exhibit a high volumetric capacitance of 425 F cm−3 (113 F g−1) in PBS and 223 F cm−3 (59.0 F g−1) in model-ISF, and an energy density of 59.1 mWh cm−3 (15.7 mWh g−1) in PBS and 30.9 mWh cm−3 (8.2 mWh g−1) in model-ISF. These devices show stability over 100,000 charging-discharging cycles without loss of capacitance in these electrolytes. Polyethylene glycol coatings on SIROF are also investigated as a potential means of controlling biomolecule absorption and enhancing biocompatibility. This work provides a step toward implantable micro-supercapacitors that directly use the biological fluids as electrolytes.

Carbon nanotube-based flexible biocathode for enzymatic biofuel cells by spray coating

Enzymatic biofuel cells are emerging technologies which gain a lot of interest as a power source for implantable devices. Effective enzyme wiring and simplification of the cell architecture are the main limitations of the fuel cell development nowadays. In the present study, spray coating was used as a reliable process to produce flexible biocathodes. That was achieved through spray coating of a conductive ink formulated by surfactant assisted carbon nanotubes dispersion. A thin continuous layer of carbon nanotubes (CNTs) was successfully coated on top of a gas diffusion layer paper. The film thickness was modulated by varying the CNT load in the ink and the number of deposited layers. It varied between 1 and 7.8 μm for a number of deposited layers between 5 and 100. Laccase enzyme was then wired to printed CNT electrodes thanks to the host-guest interaction between the hydrophobic pocket of laccase and pyrene-adamantane. Electrochemical investigations showed that laccase was effectively wired to the CNTs and presented a favorable orientation toward oxygen reduction. The biocathode current density was dependent of the number of deposited CNT layers and reached an optimum at 170 μA cm−2 for 50 deposited layers.