PORTEFEUILLE

The development of green, low-cost and disposable micro power sources that can be self-sustainable are highly needed in the field of biobatteries, ingestible medical devices, wearable sensors, and smart textiles. Moreover, the improvement of small-scale devices that can be globally used to temporarily collect real-time information from the environment are highly required. To achieve a fully biodegradable battery we will develop water-based inks composed of cellulose and cellulose derivatives. For this purpose, two generations of biobatteries using fungi as oxidation catalyst will be manufactured; (i) The first generation will target short single use operation and will stop working when the provided source of nutrients is depleted by the fungus. (ii) The second generation will have an extended lifetime owing to the combination of fungi and microalgae working in symbiosis - the microalgae will provide the carbon source for the fungus and the fungus will provide the mineral nutrients for the microalgae - to ensure extended operation for continuous sensing functionality. This generation of biobattery will continuously operate until it is decomposed into its surroundings. The biobattery will be made of a continuous nanocellulose sheet that the user will assemble in a simple two-step folding process, and activated by providing a small volume (~1 mL) of water to the dormant microorganisms. The objective is that the results of this project leads to an Empa spin-off company that aims to bring the developed fungal biobatteries to the market.

This project aims at solving the key challenge to develop a reliable technology that can autonomously and efficiently provide stable electrical supply even in resource-limited environments. Additionally, a successful development of green, low-cost and disposable power source that can be self-sustainable may assist in moving the research and technological developments within the fields of environmental sensing, ingestible medical devices, wearable sensors, and smart textiles forward.

During the first year, we screened different fungi with potential metabolism that could be used for our biobatteries concept. The enzymatic pathways of the fungal metabolism were fully characterized and the optimized conditions for the growth of the selected fungi were identified. Additionally, printing conditions and viability of the selected fungi by using cellulose-based inks were fully optimized. 

During the second year we studied the interactions between co-cultures of white rot fungi and freshwater microalgae. We could show their symbiotic growth in cellulose gels and compatibility with 3D printing for integration in biobatteries. Additionally, we could show that a custom developed current collector can be 3D-printed for use in our battery system. Furthermore, we could monitor the growth of fungi and electrochemically characterize them in conductive carbon-based inks. These fungal inks were used as electrodes in the biobatteries. The design of final printed biobattery demonstrators were also initiated.

During the third and final year we tested preservation methods that could be used on the biobattery. We developed quantitative methods to determine the number of fungal cells in inks and their enzymatic activities in inks. We could relate their cell numbers and enzyme activities to the amount of voltage produced by the biobattery. We completed an organic enclosure for potential use with the biobattery and could show its disintegration overtime at high and low temperatures. We also completed development of the fungal-based cathode and could assemble a working biobattery that powered a sensor for several days.

Reyes C, Sajó Z, Lucas MS, Ashutosh S, Schwarze FWMR, Ribera J, Nyström G. (2022) Cocultivation of white-rot fungi and microalgae in the presence of nanocellulose, M Spectrum. 10(5): e03041-22
Reyes C, Poulin A, Nyström G, Schwarze FWMR, Ribera J (2021) Endoglucanse and laccase activities of five white rot fungi in the presence of TEMPO oxidized cellulose, J Fungi. 7(3): 222