Better chemistry for building better bioreplicating robots

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Modeling muscle-brain crosstalk could help understand biology and build better robots,, TheDigitalArtist,, CC0

Understanding muscle-brain signaling could help build better robots

Unravelling the molecular details of how signals are generated and flow between muscles and the brain could help our understanding of the body and disease, but also help build better robots. Toribio Otero and Samuel Beaumont, at the Technical University of Cartagena in Spain are working towards this unusual dual aim using a model system composed of salt ions in solution, molecular machines made of electrically conductive polymers, and electrical signals traveling through wires. They discuss the work in Sensors and Actuators B: Chemical.

“The basic question behind this paper is how a muscle generates the nervous signal informing the brain about the muscle fatigue state,” Otero explains. Robots also need to be sensitive to fatigue, to avoid damaging their systems, hence the work neatly combines some of the requirements for understanding both living and robotic processes.

In the experimental set-up, a film of the synthetic polymer “polypyrrole” represents the chemical matrix inside muscle cells. The film expands during a chemical change called oxidation, where electrons are lost, and it contracts during the reverse process called reduction.

Alterations in the concentrations of the electrically charged sodium and chloride ions in the polypyrrole film accompany the reversible oxidation and reduction reactions that mimic muscle contraction. Those changes also generate electrical sensing signals transmitted to inform a computer about the ion concentrations, which in turn sends electrical signals back to influence what is happening in the model muscle as it adapts to the varying ion concentrations.

The set-up is a long way from a real muscle and brain, but Otero believes it is revealing useful information about how chemical reactions in a muscle can initiate signals to advise the brain. He suggests the results will help to create better robotic systems that will grow ever closer to what happens in real life.

“Our work demonstrates how the actuation reaction—the chemical process causing muscle contraction— can also create the sensory signal,” says Otero. He points out that the link between these two processes in living systems remains unclear and has been controversial.

In the context of robotics, he says, “These studies can improve the efficiency of artificial sensing-muscles required for the construction of bioreplicating robots.” He explains that existing robotic systems create movement and the signals that sense movement separately. If the research results can help engineers to use the same chemical processes to generate both movement and sensory signals, this could greatly simplify the construction of robots and make them more elegant and efficient mimics of our bodies.

Otero, T. F. and Beaumont, S.: "The cooperative actuation of polypyrrole electrochemical machines senses the chemical conditions as muscles sense their fatigue state," Sensors and Actuators B: Chemical (2018)