A recent article in Small describes a new type of biobattery that uses a commercial blend of 15 probiotic strains. The device is built on water-soluble or pH-responsive materials. After use, it dissolves and releases only beneficial microbes.
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Background
There are many ways to harvest energy, including thermoelectric, solar, mechanical, and radiofrequency systems. Among these, microbial fuel cells (MFCs) are a promising option for powering short-term, or "transient," electronics. These devices rely on microbes to convert natural resources into electricity through their metabolic activity.
Microbes are well-suited for this role because they can survive in harsh and changing environments. This makes them useful in a wide range of conditions. As a result, microbe-powered biobatteries have been developed as self-contained power sources for short-term and environmentally friendly electronics.
However, some of these systems raise concerns about health risks. The microbes used can be toxic, which means the batteries often have to be safely destroyed after use, usually by incineration.
To avoid this problem, the study introduces a dissolvable biobattery that uses probiotics. These are commonly used in food and supplements and are known to be safe.
Methods
The team used a probiotic blend containing 15 strains, which was purchased from a commercial source. For comparison, they also tested Shewanella oneidensis MR-1, a well-known microbe used in fuel cells.
Bacterial cells were immobilized on the anode using 2. 5% glutaraldehyde in 0.1 M phosphate-buffered saline. The mixture was left to incubate overnight. They then printed microfluidic patterns onto a water-soluble paper using wax.
The anode was drawn by hand using HB-grade pencil graphite, creating a conductive surface over the reservoir. The cathode was made with a Prussian Blue-based trace drawn in a similar way.
To delay how quickly the device dissolved, they coated the paper with a low pH-sensitive polymer called EUDRAGIT EPO. The coating was applied evenly to make sure the entire surface was covered. This helped control when the battery would activate and how long it would last.
To improve performance, the team used additional materials on both electrodes. The anode was coated with a mix of polypyrrole (PPy) and zinc oxide (ZnO₂), and the cathode used a combination of Prussian Blue and manganese dioxide (MnO₂).
The battery's electrical output was comprehensively analyzed using a data acquisition system, determining its open-circuit voltage (OCV), current-voltage (I-V) characteristics, and power output. Furthermore, the electrochemical properties of the anodic and cathodic materials were evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy.
Results and Discussion
Testing showed that the probiotic blends were capable of generating electricity. These bacteria are Gram-positive, which means they have thick cell walls. This can make it harder for electrons to move out of the cells. As a result, their ability to transfer electrons was limited, but still measurable.
In the electrochemical tests, the researchers saw oxidation peaks near +0.1 V and reduction peaks near −0.6 V. These values confirmed that the bacteria could take part in redox reactions. The reduction peaks were stronger, which suggested that the reaction was primarily one-way. The bacteria either stayed in a reduced state or used up the reduced chemicals before they could reverse.
The graphite electrode alone produced very little power. Even when paired with a strong microbe like S. oneidensis, the results were weak. To address this, the researchers added PPy-ZnO₂ to the anode.
This improved conductivity and helped support electricity generation from probiotic strains that have lower activity. This material choice made the device more suitable for short-term, single-use applications.
Initially, the battery only worked for about 30 minutes. It also couldn’t be reliably activated in wet environments. Adding the EUDRAGIT EPO coating helped with both issues. Without this coating, the device stopped working within 15 minutes of being in water.
With the coating, it lasted up to 75 minutes. When a second external coating was applied, the battery worked for more than 100 minutes. However, this extra layer slightly lowered its peak performance.
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Conclusion
This study shows that a dissolvable, probiotic-powered biobattery can serve as a safe and eco-friendly energy source for short-term use. By using probiotics as the active microbes, the device avoids the safety concerns linked to other types of biobatteries.
Adding PPy-ZnO₂ to the anode helped increase electron transfer. Using a Prussian Blue-MnO₂ mix on the cathode improved overall battery performance. The device could provide power for a longer time while still breaking down in a controlled way after use.
This approach could support new kinds of temporary systems, such as medical implants, disposable sensors, and environmental monitoring tools.
Journal Reference
Rezaie, M., Mohammadifar, M., Choi, S. (2025). Dissolvable Probiotic‐Powered Biobatteries: A Safe and Biocompatible Energy Solution for Transient Applications. Small. DOI: 10.1002/smll.202502633, https://onlinelibrary.wiley.com/doi/10.1002/smll.202502633
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