During the COVID-19 pandemic, while some people were experimenting with homemade bread, others were focused on beverage fermentation. Kombucha was the focus of this trend, as it was perceived as a healthy drink that boosts the immune system. Kombucha consumption continues today, and a research group led by Yu Jun Tan, assistant professor in the Department of Mechanical Engineering at the College of Design and Engineering, National University of Singapore, has found a way to turn waste from kombucha tea fermentation into materials for sustainable electronics.
To start the fermentation and obtain a kombucha drink, you need a “SCOBY”, which stands for Symbiotic Culture of Bacteria and Yeasts. As the fermentation proceeds, the SCOBY gets bigger and bigger. Most of the SCOBY is composed of kombucha bacterial cellulose, a biopolymer that is a waste byproduct of the kombucha tea fermentation process.
“This bacterial cellulose is a strong, flexible, and completely biodegradable material,” says Tan. “I like to try new things in the kitchen, and brewing kombucha is one of my favourite experiments. Watching the SCOBY grow gave me a first-hand appreciation for how this natural bacterial cellulose forms and how strong and versatile it can be. That’s why we chose it as a starting point for sustainable electronics.”
Today, petroleum-based polymers are indispensable components in electronics. As human reliance on modern electronics grows, the accumulation of electronic waste poses increasing environmental challenges; seeing the urgent need to find alternative sustainable materials, Tan’s team decided to explore the leftover material from kombucha tea fermentation—a renewable, abundant material that normally gets discarded as waste—as an unexpected, eco-friendly alternative.
Turning a Home-Brew Trend into a Scientific Opportunity
Besides bacterial cellulose, the SCOBY contains live organisms — bacteria and yeasts. To make it a suitable substrate for electronics manufacturing, the team had to purify the cellulose film, making it uniform, stable, and sterile.
“We used just hydrogen peroxide and baking soda (things you’d find in any household) to purify the kombucha cellulose,” says Tan. Using a powerful microscopic technique that reveals features down to a few nanometers (hundreds to thousands of times smaller than a cell), the team observed the results after purification. They saw that the bacterial cellulose film displayed a clean, densely packed cellulose nanofiber matrix, with no traces of live material or any organic impurities. “We were pleasantly surprised by how well our simple, eco-friendly cleaning process worked,” Tan comments.
Mechanical tests on the cellulose films challenged assumptions about what sustainable materials can do. Tan’s team observed that the purified, natural film was resistant to high-temperature and humidity and had huge tensile strength.
The team combined the purified cellulose film with gold, an excellent electrical conductor, both chemically stable and biocompatible. The conductive patterns of the resulting gold electrodes remained intact even after bending and folding. The kind of mechanical stability they observed is typically associated with synthetic plastic films rather than natural materials. “It was exciting to see that something grown from a fermentation jar could perform so well,” says Tan.
Testing Biodegradability in Soil
Tan and her team wanted to demonstrate how quickly their green electronic circuit could decompose and whether the gold component would affect the surroundings due to its inability to break down.
For that, they buried a device made of kombucha bacterial cellulose film embedded with a gold-sputtered circuit next to a small plant: Vigna unguiculata unguiculata, commonly used in plant research labs because of its short life cycle and fast germination. For two months, they monitored the plant growth, comparing it with a control plant growing without a device in its surroundings.
The scientists observed that, by day ten, the bacterial cellulose component of the device became translucent, indicating that soil microbes were rapidly digesting it, while the gold circuit appeared intact by the end of the experiment. The plant next to the device grew similarly to the control one, showing no signs of stress.
According to Tan, because their cellulose films naturally decompose in soil, they’re ideal for devices meant to disappear after use rather than become waste.
Exploring Real-World Applications
Seeing the mechanical resistance and biodegradability success, the team was ready to test applications. “We’re focusing on short-term or ‘transient’ devices, i.e., products designed to work for a specific period and then safely break down,” says Tan. “This could include medical patches, biodegradable implants, environmental sensors that monitor water quality or soil health, or even smart packaging that tracks freshness or temperature during transport.”
As a proof-of-concept, they built a pressure sensor for flatfoot assessment. They compared the electrical signals received from “normal” foot steps versus flatfoot steps. The team observed that the electronic signals recorded from flatfoot steps were lower than those from normal foot steps. “This reduction is due to a more uniform pressure distribution across the entire foot”, explains the team in their Advanced Science article. As the system could effectively distinguish between normal and flatfoot conditions, it assures the possibility of using their Kombucha-derived material for real-time diagnostic monitoring.
Tan’s research isn’t just about creating greener electronics: it shows a new way of thinking about technology. “By using materials that are renewable, biodegradable, and safe,” Tan remarks, “we can teach future generations that electronics don’t have to be wasteful or harmful to the environment.”
Reference: X. Y. Chan et al., From Grave to Cradle: Kombucha Waste for Sustainable Electronics, Advanced Science (2025), DOI: 10.1002/advs.202514521
Featured Image Credit: NutriScan App via Pixabay
