Human physical feats, whether nailing a guitar solo or scoring a half-court shot in basketball, require a high level of coordination between the sensory functions of our skin and the motor functions of our muscles. What kind of achievements could robots achieve with the same cohesion between perception and action?
On the medical front, researchers at the University of North Carolina (UNC) at Chapel Hill have begun to explore the possibilities.
The team developed soft robots made mainly of two layers (one simulating skin and the other muscle) that can autonomously detect and respond to different physiological stimuli. in a proof of concept study published in Nature CommunicationsThe authors tested the diagnostic and therapeutic potential of their robots in several model organs, including a mouse model of heart disease. The data suggest that this implantable technology could have broad applicability.
“Complications associated with traditional medical implants often arise from a mechanical, chemical, or functional mismatch between the device and the tissue. Our biomimetic soft robot addresses these challenges with its biocompatible, durable materials and its ability to adapt to the dynamic conditions of the body,” said study senior author Wubin Bai, Ph.D., professor of applied physical sciences at UNC-Chapel Hill.
The robot’s base layer is composed of a thermally sensitive hydrogel that can contract and relax like a muscle, allowing the implant to bend and gently grasp organs inside the body. Attached to this muscle layer is the robot’s electronic skin, or e-skin, which is made of a soft polymer that can contain a wide variety of components (both sensors and stimulators) that can affect the robot and surrounding tissue.
The researchers designed the robot to convert sensory information into physical responses, allowing physiological changes in the body to dictate the robot’s actions. For example, e-skin sensors can detect local changes in the body’s temperature, acidity, electrical activity, and mechanical stress, while mini electrodes can stimulate tissue and electrical heaters can cause the robot’s muscle layer to contract.
They made several double-layered robots of different shapes, some taking the shape of a simple ribbon, while other multi-armed robots emulated starfish. With integrated circuits that enable wireless transmission of power and data, these devices maintained a slim profile in all configurations.
The researchers evaluated the robots through several laboratory tests they developed based on conversations with doctors about various clinical challenges.
In one test, a four-armed robot gently grasped a balloon that the researchers filled and emptied with water, simulating changes in bladder volume. The device measured the tension of the “bladder” as it filled, automatically responding with electrical stimulation to trigger emptying after reaching a certain threshold, suggesting possible utility for bladder dysfunction.
In another experiment, they showed that a robot could rotate helically around a plastic artery model to measure simulated blood pressure. This capability could relieve surgeons from performing the difficult task of manually wrapping vascular cuffs around arteries, which is done to detect blockages during certain procedures, Bai said.
The team also explored the potential of their technology for long-term drug delivery to the gastrointestinal tract. The researchers showed that the robot could easily travel through a rubber model esophagus but expand into a model stomach, which could impede its passage and lengthen the window in which drugs could be released from the device. In separate experiments, they showed that the robot could measure acidity and release a model drug.
Another series of tests took the technology to a more realistic testing ground: a beating heart.
Some critical heart surgeries require placing a device on the heart surface that delivers electrical stimulation to create a normal heart rhythm while the organ recovers. But when these traditional flat devices are connected to curved, beating heart tissue, the interface generates stress that can disrupt normal heart function, Bai explained.
The researchers placed four-armed robots on the surface of live mouse hearts, where the wet hydrogel of the artificial muscle gently adhered and gripped the heart tissue.
The authors discovered that the technology could measure heart muscle activity and modulate it through electrical stimulation. They detected no signs of inflammation or injury two weeks after implantation.
Bai and his colleagues hope their robots will eventually help human patients, but before that, they plan to add functionality to the technology and evaluate it in animal models that closer match our physiology.
“Inspired by our own versatile tissues, these researchers are developing a robotic tool that shows similar versatility to address many challenges in the biomedical space,” said Tiffani Lash, Ph.D., program director of the Division of Health Informatics Technologies at the National Institute of Biomedical Imaging and Bioengineering (NIBIB).
This research was supported in part by a NIBIB grant (R01EB034332).
This prominent scientist describes a basic research finding. Basic research increases our understanding of human behavior and biology, which is critical to promoting new and better ways to prevent, diagnose, and treat diseases. Science is an unpredictable and incremental process: each research advance builds on past discoveries, often in unexpected ways. Most clinical advances would not be possible without knowledge of fundamental basic research.
Study reference: Lin Zhang et al. Skin-inspired sensory robots for electronic implants. Nature communications. DOI: 10.1038/s41467-024-48903-z
