McGill Researchers Unveil Stretchable, Eco-Friendly Battery

Researchers at McGill University have developed a groundbreaking stretchable and biodegradable battery, potentially transforming the landscape of wearable and implantable devices. The innovative battery, created by the team at the Trottier Institute for Sustainability in Engineering and Design, utilizes eco-friendly materials, specifically citric and lactic acid combined with gelatin, to enhance flexibility and performance while minimizing environmental impact.

The research, led by Sharmistha Bhadra, an Associate Professor of Electrical and Computer Engineering, aims to tackle the pressing issue of electronic waste. “We use a lot of batteries in our lab for wearable devices, and they eventually stop working and get thrown out,” Bhadra explained. “This project asked whether we could make something biodegradable and stretchable that still performs well.”

Innovative Materials and Design

Traditional batteries often rely on heavy metals that can be harmful to the environment. In a significant departure from conventional designs, McGill researchers replaced these toxic components with magnesium and molybdenum, both known for their biodegradable properties. Previous studies indicated that magnesium-based biodegradable batteries typically underperformed compared to conventional alternatives.

To address this challenge, the team experimented with lactic acid and citric acid mixed with gelatin. Their findings revealed that these acids improved battery performance. “Magnesium can generate a layer that stops the reaction between electrolyte and electrode,” said Junzhi Liu, the doctoral student who led the development and testing of the battery. “We found we could break down this layer with citric or lactic acid and increase the battery’s lifetime and its voltage.”

The inspiration for using citric acid stemmed from a simple childhood science project involving lemon batteries, where the acidity facilitates the generation of electricity. Bhadra noted, “Many people make a lemon battery as kids, where you connect a copper wire to a light. The lemon has enough ions to conduct electricity.”

Stretchability and Real-World Applications

To enhance the battery’s stretchability, the researchers incorporated both acids into a gelatin matrix and applied a kirigami design—a technique that enables materials to bend and stretch without damage. This approach is relatively novel in the context of biodegradable batteries, allowing the team to stretch the battery up to 80 percent without compromising its performance.

In testing, the battery produced slightly less power than a standard AA battery, registering 1.3 volts compared to the typical 1.5 volts. Bhadra stated, “We wanted to see if we could run an actual wearable or sensor, so Junzhi built a touch-sensitive device worn on a finger and powered by the battery.” This versatile design holds promise not only for medical implants and wearables but also for flexible Internet-of-Things devices.

The team is actively seeking industry partners to advance their research. Future goals include enhancing the battery’s performance, miniaturizing it for implantable use, and integrating it with biodegradable circuits. “The whole motivation is to address the growing problem of electronic waste,” Bhadra remarked. “If you go to a landfill, you see discarded electronics piled up for years. We are not very good about recycling [e-waste]; much of it ends up in lower-income countries. Maybe we can solve a part of the problem by developing biodegradable electronics.”

The findings of this significant study, titled “Gelatin-Organic Acid-Based Biodegradable Batteries for Stretchable Electronics,” were published in the journal Advanced Energy and Sustainability Research in August 2025. This research was funded by the McGill Sustainability Systems Initiative, highlighting the university’s commitment to addressing environmental challenges through innovative technology.