Portable bio-battery uses living hydrogels for targeted nerve signal modulation

Bio-batteries constructed by electroactive microorganisms have unique advantages in physiological monitoring, tissue integration, and powering implantable devices due to their superior adaptability and biocompatibility. However, the development of miniaturized and portable bio-batteries that are plug and play and compatible with existing devices remains a challenge.

In a study published in Advanced Materials, a team led by Zhong Chao, Liu Zhiyuan, and Wang Xinyu from the Shenzhen Institutes of Advanced Technology of the Chinese Academy of Sciences, collaborating with Wang Renheng from the Shenzhen University, developed a miniaturized, portable bio-battery that enables precise control over bioelectrical stimulation and physiological blood pressure signals.

The researchers encapsulated Shewanella oneidensis MR-1 biofilms within alginate hydrogels to develop living hydrogels, which can be 3D printed into defined geometries for customized fabrication. Inspired by lithium-ion battery fabrication, they developed a miniaturized bio-battery (20 mm in diameter, 3.2 mm in height) using living hydrogel as the bio-anode ink, K₃[Fe(CN)₆]-containing alginate hydrogel as the cathode ink, and a Nafion membrane as the ion exchange membrane.

The bio-battery generated electricity from the metabolic activity of bacteria, enabling it with self-charging capabilities up to 10 cycles. It could also serve as a pseudo-battery for charge/discharge cycles with a coulombic efficiency of more than 99.5% across 50 cycles, indicating lower energy losses. Impressively, the bacteria in the bio-battery maintained a high viability of more than 70% across the entire process and 97.6% at the end of operation.

The bio-battery exhibited a specific capacity of 0.4 mAh g⁻¹, a maximum power density of about 8.31 µW cm⁻², and an energy density of 0.008 Wh/L. Although these values are lower than those of traditional lithium-ion batteries, the bio-battery provides a sustainable energy alternative by avoiding the use of critical raw materials such as cobalt and lithium, as well as environmentally hazardous components such as manganese and organic electrolytes.

Furthermore, the researchers explored the application potential of the bio-battery in nerve stimulation. By targeting the sciatic and vagus nerves, they demonstrated its precise control over bioelectrical stimulation and physiological blood pressure signals. This precise stimulation technique holds promise for developing novel physical therapy methods.

This study promotes the development of portable bio-devices while expanding the research frontiers in engineered living energy materials. It offers innovative solutions for the future development and application of sustainable energy.