A University of Nebraska-Lincoln engineering team is another step closer to developing soft robotics and wearable systems that mimic the ability of human and plant skin to detect and self-heal injuries.
Engineer Eric Markvicka, along with graduate students Ethan Krings and Patrick McManigal, recently presented a paper at the IEEE International Conference on Robotics and Automation in Atlanta, Georgia, that sets forth a systems-level approach for a soft robotics technology that can identify damage from a puncture or extreme pressure, pinpoint its location and autonomously initiate self-repair.
The paper was among the 39 of 1,606 submissions selected as an ICRA 2025 Best Paper Award finalist. It was also a finalist for the Best Student Paper Award and in the mechanism and design category.
The team's strategy may help overcome a longstanding problem in developing soft robotics systems that import nature-inspired design principles.
"In our community, there is a huge push toward replicating traditional rigid systems using soft materials, and a huge movement toward biomimicry," said Markvicka, Robert F. and Myrna L. 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."
To fill that gap, his team developed an intelligent, self-healing artificial muscle featuring a multi-layer architecture that enables the system to identify and locate damage, then initiate a self-repair mechanism -- all without external intervention.
"The human body and animals are amazing. We can get cut and bruised and get some pretty serious injuries. And in most cases, with very limited external applications of bandages and medications, we're able to self-heal a lot of things," Markvicka said. "If we could replicate that within synthetic systems, that would really transform the field and how we think about electronics and machines."
The team's "muscle" -- or actuator, the part of a robot that converts energy into physical movement -- has three layers. The bottom one -- the damage detection layer -- is a soft electronic skin composed of liquid metal microdroplets embedded in a silicone elastomer. That skin is adhered to the middle layer, the self-healing component, which is a stiff thermoplastic elastomer. On top is the actuation layer, which kick-starts the muscle's motion when pressurized with water.
To begin the process, the team induces five monitoring currents across the bottom "skin" of the muscle, which is connected to a microcontroller and sensing circuit. Puncture or pressure damage to that layer triggers formation of an electrical network between the traces. The system recognizes this electrical footprint as evidence of damage and subsequently increases the current running through the newly formed electrical network.
This enables that network to function as a local Joule heater, converting the energy of the electric current into heat around the areas of damage. After a few minutes, this heat melts and reprocesses the middle thermoplastic layer, which seals the damage -- effectively self-healing the wound.
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