Engineers develop self healing muscle for robots (19459000)
A University of Nebraska-Lincoln team of engineers has taken another step towards developing soft robotics, wearable systems and other wearable devices that mimic the ability of skin on humans and plants to detect and self heal injuries.
Eric Markvicka and graduate students Ethan Krings and Patrick McManigal presented a paper recently at the IEEE International Conference on Robotics and Automation, held in Atlanta, Georgia. The paper outlines a systems-level method for a soft robots technology which can identify damage caused by a puncture, pinpoint its location and initiate autonomous self-repair. The paper was selected as a finalist for the ICRA 2025 Best Paper Award from among 1,606 submissions. It was also a semifinalist for the Best Student Paper Award, and in the mechanism-and-design category.
This team’s strategy could help overcome a long-standing problem in developing soft robots systems that incorporate nature-inspired design principles. Markvicka is Robert F. and Myrna Krohn Assistant professor of Biomedical engineering. “While we’ve been able to create stretchable electronics and actuators that are soft and conformal, they often don’t mimic biology in their ability to respond to damage and then initiate self-repair.”
His team filled this gap by developing an intelligent, self healing artificial muscle with a multi-layer structure that allows the system to detect and locate damage before initiating a self repair mechanism – all without external intervention. Markvicka said. “If we could replicate that within synthetic systems, that would really transform the field and how we think about electronics and machines.”
“muscle” – or the actuator, which is the part of a robotic system that converts energy to physical movement – has three layers. The bottom layer, the damage detection layer, is a soft electronic surface composed of liquid metal nanodroplets embedded in silicone elastomer. The skin is attached to the middle layer of the self-healing component which is a thermoplastic elastomer. The actuation layer is on top, which starts the muscle’s movement when water pressure is applied.
The team initiates the process by introducing five monitoring currents along the bottom “skin” [of the muscle]which is connected to the microcontroller and sensor circuit. A puncture or pressure damage in that layer triggers the formation of an electric network between the traces. The system recognizes the electrical footprint as evidence for damage and increases the current flowing through the newly formed network. This allows the network to act as a local Joule heat source, converting the energy from the electric current in the damaged areas into heat. After a few moments, the heat melts the middle thermoplastic layers, sealing the wound.
Resetting the system to its original state is the last step. This is done by erasing any electrical footprint left on the bottom layer. Markvicka’s group is using the electromigration process to achieve this. This involves an electrical current that causes metal atoms migrate. The phenomenon has traditionally been viewed as a hindrance to metallic circuits, because moving atoms cause gaps and deform the materials of a circuit, leading to device failures and breakage.
The researchers have used electromigration in a major innovation to solve a long-standing problem that has plagued their efforts to develop an autonomous, self healing system: the apparent permanence of the damage-induced, electrical networks at the bottom layer. The system is unable to complete more than one cycle between damage and repair without the ability of resetting the baseline monitoring traces.
The researchers realized that electromigration, with its ability of physically separating metal ions and triggering open-circuit fail, might be the key for erasing newly formed traces. The strategy worked. By increasing the current, the team was able to induce thermal failure and electromigration mechanisms that reset the damage-detection network. Markvicka said. “It’s one of the bottlenecks that has prevented the miniaturization of electronics. We use it in a unique and really positive way here. Instead of trying to prevent it from happening, we are, for the first time, harnessing it to erase traces that we used to think were permanent.”
The autonomously self-healing technologies has the potential to revolutionize a number of industries. In agricultural states such as Nebraska, this technology could be a boon to robotics systems which are frequently exposed to sharp objects, like twigs and thorns. It can also be used in wearable health monitoring devices that must withstand daily wear and tear. It could also revolutionize wearable devices for health monitoring that must withstand daily wear.
This technology would also be beneficial to society in general. Most consumer electronics have a lifespan of only one to two years. This leads to billions pounds of electronic waste every year. This waste contains toxic substances like lead and Mercury, which are harmful to human and environmental health. Self-healing technologies could help stem this tide.
“If we can begin to create materials that are able to passably and autonomously detect when damage has happened, and then initiate these self-repair mechanisms, it would really be transformative,” Markvicka stated.
