In a breakthrough that could transform bioelectronic sensing, an interdisciplinary team of researchers at Rice University has developed a new method to dramatically enhance the sensitivity of enzymatic and microbial fuel cells using organic electrochemical transistors (OECTs). The research was recently published in the journal Device .
The innovative approach amplifies electrical signals by three orders of magnitude and improves signal-to-noise ratios, potentially enabling the next generation of highly sensitive, low-power biosensors for health and environmental monitoring.
"We have demonstrated a simple yet powerful technique to amplify weak bioelectronic signals using OECTs, overcoming previous challenges in integrating fuel cells with electrochemical sensors," said corresponding author Rafael Verduzco , professor of chemical and biomolecular engineering and materials science and nanoengineering. "This method opens the door to more versatile and efficient biosensors that could be applied in medicine, environmental monitoring and even wearable technology."
Traditional biosensors rely on direct interactions between target biomolecules and the sensor device, which can pose limitations when the electrolyte environment is incompatible. This research circumvents that challenge by electronically coupling fuel cells with OECTs instead of introducing biomolecules directly into the sensor.
"One of the biggest hurdles in bioelectronic sensing has been designing systems that work in different chemical environments without compromising performance," said corresponding author Caroline Ajo-Franklin , professor of biosciences, director of the Rice Synthetic Biology Institute and Cancer Prevention and Research Institute of Texas Scholar. "By keeping the OECT and fuel cell separate, we ensured optimal conditions for both components while still achieving powerful signal amplification."
OECTs are thin-film transistors that operate in aqueous environments and have gained attention for their high sensitivity and low-voltage operation. For the study, the team integrated OECTs with two types of biofuel cells to enhance their performance. The first type, enzymatic fuel cells, utilize glucose dehydrogenase to catalyze glucose oxidation, generating electricity in the process. The second type, microbial fuel cells, rely on electroactive bacteria to metabolize organic substrates and produce current. The OECTs were then coupled with the fuel cells in two different configurations: a cathode-gate configuration and an anode-gate configuration.
The researchers found that OECTs can amplify signals from enzymatic and microbial fuel cells by factors ranging from 1,000 to 7,000 depending on the configuration and fuel cell type. This amplification is significantly higher than traditional electrochemical amplification techniques, which typically achieve signal enhancements in the range of 10 to 100 times stronger.
The team discovered that the cathode-gate configuration provided the best amplification, especially when using a specific polymer as the channel material. The anode-gate configuration also showed strong amplification but posed potential challenges at higher fuel cell currents, leading to irreversible degradation in some cases.
Along with boosting signal strength, the researchers found that OECTs also reduced background noise, making measurements more precise. Traditional sensors can struggle with interference and weak signals, but the OECTs produced clearer, more reliable data.
"We observed that even tiny electrochemical changes in the fuel cell were translated into large, easily detectable electrical signals through the OECT," said Ravindra Saxena, co-first author of the study and graduate student in the applied physics program at Rice's Smalley-Curl Institute. "This means that we can detect biomolecules and contaminants with much greater sensitivity than before."
The real-world applications for this technology are vast, and the research team successfully demonstrated a miniaturized version of the system on a single glass slide, proving that the technique is scalable and can be used in portable biosensors.
One of the most promising applications is arsenite detection — a critical need in water safety. The team engineered E. coli bacteria with an arsenite-responsive extracellular electron transfer pathway, enabling them to detect the presence of arsenite at concentrations as low as 0.1 micromoles per liter with a clear, measurable response from the OECT-amplified signal.
Beyond environmental applications, the system could revolutionize wearable health monitoring, where power-efficient and highly sensitive biosensors are in high demand. For example, lactate sensing in sweat, which is an indicator of muscle fatigue, was successfully demonstrated using microbial fuel cells.
"Athletes, medical patients and even soldiers could benefit from real-time metabolic monitoring without the need for complex, high-power electronics," said co-first author Xu Zhang, a postdoctoral fellow in the Department of Biosciences.
The researchers emphasized that understanding the power dynamics between OECTs and fuel cells is key to optimizing sensor performance, and they identified two distinct operational modes. In the power-mismatched mode, the fuel cell generates less power than the OECT requires, leading to higher sensitivity but operating closer to short-circuit conditions. In contrast, the power-matched mode occurs when the fuel cell produces sufficient power to drive the OECT, resulting in more stable and accurate readings.
"By fine-tuning these interactions, we can design sensors tailored for different applications, from highly sensitive medical diagnostics to robust environmental monitors," Verduzco said. "We believe this approach will change how we think about bioelectronic sensing. It's a simple, effective and scalable solution."
This research was sponsored by the Army Research Office, the Cancer Prevention and Research Institute of Texas and the National Science Foundation.
