Modular, neuromorphic electronic skin capable of active pain and injury perception in robotic applications. Credit: Xinge Yu, City University of Hong Kong
If you accidentally put your hand on a hot object, you'll naturally pull it away fast, before you have to think about it. This happens thanks to sensory nerves in your skin that send a lightning-fast signal to your spinal cord, which immediately activates your muscles. The speed at which this happens helps prevent serious burns. Your brain is only informed once the movement has already started.
If something similar happens to a humanoid robot, it typically has to send sensor data to a central processing unit (CPU), wait for the system to process it, and then send a command to the arm's actuators to move. Even a brief delay can increase the risk of serious damage.
But as humanoid robots move out of labs and factories and into our homes, hospitals and workplaces, they will need to be more than just pre-programmed machines if they are to live up to their potential. Ideally, they should be able to interact with the environment instinctively. To help make that happen, scientists in China have developed a neuromorphic robotic e-skin (NRE-skin) that gives robots a sense of touch and even an ability to feel pain.
Current robot skins are really nothing more than pressure pads that can tell when they are being touched but can't process the meaning, such as whether it's painful. The NRE-skin is different because it is designed to function like the human nervous system.
How it works
This skin consists of four layers. The top layer is a protective cover that acts like our own epidermis. Below that are sensors and circuits that behave like human nerves. Every 75–150 seconds, the skin sends a small electrical pulse to the robot's CPU even when nothing is touching it. This is like the skin's way of saying, "Everything is fine." If the skin is cut or damaged, the pulse stops, which tells the robot where it has been injured, and it alerts the owner.
When the skin is touched, it sends a different kind of signal called a spike, which carries information about the pressure being applied. For normal touches, these spikes go to the CPU. However, if the touch is so hard or extreme that it causes "pain," the skin sends a high-voltage spike directly to the motors. This bypasses the CPU and triggers a rapid reflex reaction, such as pulling its arm away instantly. A pain signal is emitted only when sensors in the skin detect a force exceeding a preset threshold.
"Our neuromorphic robotic e-skin features hierarchical, neural-inspired architecture enabling high-resolution touch sensing, active pain and injury detection with local reflexes, and modular quick-release repair," wrote the team in their paper published in the Proceedings of the National Academy of Sciences. "This design significantly improves robotic touch, safety, and intuitive human-robot interaction for empathetic service robots."
The skin can even "repair" itself thanks to a clever, Lego-like design. Because it is made of magnetic patches, an owner can simply snap off a damaged section and click a new one into place in seconds.
The next step for the team is to improve the skin's sensitivity so it can feel multiple touches at once without being confused.
Written for you by our author Paul Arnold, edited by Lisa Lock, and fact-checked and reviewed by Andrew Zinin—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.
