NUS researchers have developed a groundbreaking electronic skin technology that could revolutionize underwater robotics and human-machine interfaces. This self-healing magnetoelectric sensory system (SMES) is designed to mimic the protective and regenerative capabilities of biological skin, offering a unique solution to the challenges faced by underwater devices and sensors.
A Skin-Inspired Solution
The SMES draws inspiration from the remarkable abilities of biological skin. It can detect touch and proximity, much like our skin senses pressure and objects around us. But what sets it apart is its self-healing nature. When damaged, the SMES can repair itself, just like how our skin heals after an injury. This is achieved through a clever use of a stretchable, self-healing elastomer laced with liquid-metal conductors.
When the sensor's top layer is punctured or cut, its electrical resistance spikes, indicating damage. However, the SMES's secret lies in its ability to self-repair. The soft material contains reversible molecular interactions that allow it to bind back together when two damaged surfaces come into contact. This means that even after being subjected to needle pricks, the sensor can recover its original electrical performance within seconds, all without any external intervention.
For more severe damage, such as cuts, a brief mechanical pressure triggers an initial repair, and the sensor regains full functionality after a longer healing period. The self-healing elastomer achieves impressive elastic recovery, reaching up to 92% and nearly 100% healing efficiency under water after a specified time frame. This level of self-healing is a significant advancement, especially for materials that struggle to bond back together in underwater environments.
Self-Powered and Durable
The SMES's self-powered design is another remarkable feature. It generates its own electrical signals through electromagnetic induction, eliminating the need for an external power source. This is particularly advantageous in underwater settings, where battery access is limited. Inside the device, a small magnet and a coil of liquid-metal wire work together. When an object presses on the sensor or moves close to it, the magnet's position changes relative to the coil, inducing a voltage. This enables both proximity sensing and tactile sensing, allowing the device to detect nearby objects and measure applied pressure.
The SMES demonstrated exceptional performance, with a response time of approximately 41 milliseconds, which is ten times faster than the blink of an eye. It also maintained stable output after 10,000 cycles of usage, a benchmark for electronic skins. Even after 10 days of underwater immersion, including in simulated seawater, the proximity-sensing performance remained consistent, showcasing its durability and reliability.
From Gloves to Robotic Hands
To showcase the real-world applications of the SMES, the research team built two prototypes. The first is a smart diving glove designed for wireless underwater communication. Sensors on each fingertip generate distinct voltage patterns for different hand gestures, which are then transmitted via Bluetooth to a smartphone. This allows divers to convey status updates and commands without speaking, making underwater communication more efficient.
The glove also features a damage sensor with red LEDs that light up when severe damage is detected, providing a real-time visual warning to the diver. The second prototype is a robotic hand fitted with the SMES technology for underwater grasping and delivery tasks. It uses three LEDs to indicate the sensor's damage status, with green for normal operation, yellow for minor damage, and red for severe structural damage.
During testing, the robotic hand successfully grasped and transported objects underwater while detecting and recovering from puncture damage caused by sharp shells. This demonstrates the SMES's ability to function reliably in harsh underwater conditions, even when damaged.
Looking Ahead
Assistant Professor Tan Yu Jun, the lead researcher, envisions a future where SMES technology is integrated into real robots, prosthetics, and wearable devices. The goal is to create soft machines that can sense their surroundings, recognize damage, and recover their function, much like living skin. This technology has the potential to enhance the durability and self-sufficiency of underwater devices, making them more reliable and safer for divers and underwater robots.
The research, published in Advanced Materials, showcases the incredible potential of bio-inspired technology. By mimicking the protective and regenerative mechanisms of biological skin, NUS researchers have developed a self-healing magnetoelectric sensory system that could transform the way we interact with underwater environments, opening up new possibilities for soft robotics and human-machine interfaces.
