Compact and Portable Bio-Battery Using Living Hydrogel for Targeted Nerve Stimulation

Living hydrogels to prepare portable energy devices for neuron stimulation

A research team led by ZHONG Chao, LIU Zhiyuan, and WANG Xinyu from the Shenzhen Institutes of Advanced Technology (SIAT), Chinese Academy of Sciences, in partnership with WANG Renheng from Shenzhen University, has developed a compact and portable bio-battery measuring just 20 millimeters in diameter and 3.2 millimeters in height.

This cutting-edge device features an integrated bioelectric stimulation system that allows for precise regulation of bioelectrical signals and physiological blood pressure, showing great promise for medical applications.

Published in Advanced Materials, the study marks a significant step forward in the development of portable bio-devices and broadens the scope of research in engineered living energy materials.

Bio-batteries, which use electroactive microorganisms, offer distinct advantages in physiological monitoring, tissue compatibility, and powering implantable technologies due to their high adaptability and biocompatibility. However, achieving miniaturized, plug-and-play bio-batteries that work seamlessly with existing systems has remained a technical hurdle.

In this study, the researchers developed living hydrogels by embedding Shewanella oneidensis MR-1 biofilms within alginate hydrogels, which were then 3D-printed into specific shapes for customized applications.

Drawing inspiration from lithium-ion battery design, the team created a compact bio-battery (measuring 20 mm in diameter and 3.2 mm in height) using the living hydrogel as the bio-anode ink, an alginate hydrogel containing K₃[Fe(CN)₆] as the cathode ink, and a Nafion membrane for ion exchange.

This bio-battery harnessed the metabolic activity of bacteria to generate electricity, allowing for self-recharging up to 10 cycles. It also functioned effectively in pseudo-battery mode, achieving over 99.5% coulombic efficiency across 50 charge/discharge cycles, indicating minimal energy loss. Notably, the bacteria retained strong viability throughout the process—maintaining over 70% on average and 97.6% by the end of use.

The device achieved a specific capacity of 0.4 mAh g⁻¹, a peak power density of approximately 8.31 µW cm⁻², and an energy density of 0.008 Wh/L. Although these performance metrics are lower than those of conventional lithium-ion batteries, the bio-battery offers a sustainable energy solution by eliminating the need for critical raw materials like lithium and cobalt,and avoiding environmentally harmful substances such as manganese and organic electrolytes.

Additionally, the researchers investigated the potential of bio-batteries for use in nerve stimulation. By focusing on the sciatic and vagus nerves, they were able to demonstrate accurate control of bioelectrical impulses and physiological blood pressure signals. This level of precision suggests promising applications in the development of new physical therapy techniques.

Overall, the study presents groundbreaking approaches for advancing sustainable energy technologies and their practical applications.