Yeast-driven and bioimpedance-sensitive biohybrid soft robots
image: During fermentation, yeast cells undergo division, which affects the yeast culture’s impedance. Concurrently, carbon dioxide is produced as a byproduct of fermentation, which the robot utilizes as a power source for motion. The bioimpedance frequency serves as a feedback sensor for monitoring the biological components in biohybrid.
Credit: MennaAllah Soliman, University of Sheffield.
Soft robots are celebrated in biomedical and environmental-interaction scenarios for their compliance and deformability, but truly emulating the adaptive capabilities of living organisms requires tight coupling of actuation, sensing, and control. In recent years, researchers have begun embedding living cells or active materials into artificial structures to create biohybrid robots, leveraging unique biological functions—such as contraction, metabolism, and chemical communication—to achieve more agile motion and responsive feedback. Current approaches, however, typically face hurdles such as complex design and modeling, difficulty in batch manufacturing, and instability in long-term autonomous control. Moreover, enabling a robot to autonomously manage its internal living components demands real-time monitoring of their metabolic state. Traditional muscle- or bacteria-based systems usually depend on external optical, chemical, or electrical stimulation, leading to intricate feedback loops. Bioimpedance offers a non-invasive means of measuring the electrical properties of cells or tissues and has already found use in applications like fruit-quality assessment. “Compared with expensive muscle cultures or genetically engineered bacteria, ordinary yeast cells are inexpensive and easy to cultivate; during fermentation they naturally generate CO2 pressure that can directly power pneumatic soft actuators, and their metabolic activity can be tracked through impedance spectra.” said the author MennaAllah Soliman, a researcher at University of Sheffield, “Based on this, we propose a single-resistor oscillator (SCRO) circuit combined with a digital potentiometer, which can continuously track yeast impedance in a portable size, acting as both an "engine" and a "sensor", thus completing driving and state sensing in the same system.”
This study explored the feasibility of using yeast as an actuation and sensing mechanism in soft robotics. First, the study investigated the potential of yeast as a source of mechanical power and the ability of a bioimpedance circuit to detect pressure changes. The experiments demonstrated that yeast can generate sufficient pressure for actuation, with pressure levels directly correlating with yeast impedance at a fixed volume. These findings underscore the potential for dynamic, real-time tracking of yeast-driven actuation, enabling timely adjustments for optimized fermentation performance. By integrating yeast dynamics equations with SCRO circuit equations, authors successfully modeled yeast growth rate and actuation power, paving the way for enhanced sensing and actuation capabilities in biohybrid systems. Additionally, authors observed a direct relationship between sugar concentration, actuator peak position, and the exerted force of the soft inflatable membrane actuator, indicating the influence of fermentation dynamics on actuator behavior.
Then this paper explores using 2 types of soft actuators—a soft limb and an inflatable membrane—to test the capability of yeast to actuate robots while sensing both internal and external states using bioimpedance. The experiments with soft limb designs revealed a complex interaction between yeast fermentation and robot motion, particularly regarding deflection angle under varying temperatures. By correlating impedance frequency with robot movement, authors established a method for monitoring yeast dynamics and predicting actuator behavior as a proprioceptive sensor. The results indicate that temperature variations significantly affect the acceleration and deceleration of limb motion, suggesting that temperature can effectively control yeast actuation. This study also demonstrates that yeast impedance frequency is a reliable indicator of yeast state. In the experiments involving an inflatable membrane actuator without a separate yeast chamber, authors gained insights into the practical application of yeast-driven actuation by incorporating yeast directly into the actuator. The inflatable membrane actuator effectively responded to external forces, with noticeable changes in pressure and frequency. Cross-correlation analysis showed significant positive correlations between applied force, pressure, and frequency responses.
Yeast-driven actuators hold immense potential for powering and controlling soft robotics systems. This study investigates the feasibility of using yeast for actuation and sensing in soft robotics, demonstrating that yeast fermentation can generate mechanical power and be sensed through bioimpedance. This study paves the way for enhanced biohybrid systems with integrated sensing and actuation capabilities. “While yeast-driven actuation demonstrates significant potential, several challenges and limitations must be addressed to optimize its use. For example, the high growth rate of yeast can cause rapid fluctuations in frequency readings and actuator performance, complicating precise control and long-term operation of yeast-driven robots. One critical area for future research is the deactivation process of yeast-driven actuation.” said MennaAllah Soliman.
Authors of the paper include MennaAllah Soliman, Frederick Forbes, and Dana D. Damian.
The work is supported by 2 EPSRC DTP PhD scholarships from the School of Electrical and Electronic Engineering at the University of Sheffield.
The paper, “Yeast-Driven and Bioimpedance-Sensitive Biohybrid Soft Robots” was published in the journal Cyborg and Bionic Systems on Apr. 25, 2025, at DOI: 10.34133/cbsystems.0233.