Science & Technology (Commonwealth Union) – Robots have made major advances in vision and movement, but their sense of touch has remained a significant limitation. Researchers have now created a tiny tactile sensor that could give robots a capability much closer to the human sense of touch.
The device, developed by scientists at the University of Cambridge, uses liquid metal composites and graphene—a two-dimensional form of carbon. This flexible “skin” enables robots to detect not only how much pressure they apply to an object, but also the direction of forces acting on it, whether the object is slipping, and even the texture of a surface. The sensor operates at a scale small enough to approach the spatial sensitivity of human fingertips. The findings were published in the journal Nature Materials.
Human fingertips contain several types of mechanoreceptors that work together to detect pressure, force, vibration, and texture at the same time. Replicating this kind of complex, multidimensional touch in artificial systems is extremely difficult, particularly when the technology must also be compact and robust enough for real-world applications.
Professor Tawfique Hasan of the Cambridge Graphene Centre, who led the study stated that many current tactile sensors are either too large, too delicate, too complicated to produce, or incapable of clearly distinguishing between normal and sideways forces.
He further indicated that it has been a major obstacle to developing robots capable of truly precise and skillful manipulation.
To address this challenge, the researchers created a soft and flexible composite material made from graphene sheets, deformable metal microdroplets, and nickel particles, all embedded within a silicone base.
Taking inspiration from the microscopic structures of human skin, the team formed the material into tiny pyramid shapes, some measuring just 200 micrometres across. These pyramids focus stress at their tips, allowing the sensor to pick up extremely small forces while still covering a broad measurement range.
The finished tactile sensor is sensitive enough to detect something as small as a grain of sand. Compared with current flexible tactile sensors, the new design reduces size and improves detection limits by about an order of magnitude.
In addition, the sensor can differentiate between shear forces and direct pressure, enabling it to recognise when an object starts to slip. By analysing signals from four electrodes positioned beneath each pyramid, the device can reconstruct the complete three-dimensional force vector in real time.
“Our approach shows that bulky mechanical structures or complex optics are not required to achieve high-resolution 3D tactile sensing,” explained lead author Dr Guolin Yun, a former Royal Society Newton International Fellow at Cambridge, and present Professor at the University of Science and Technology of China. “By combining smart materials with skin-inspired structures, we achieve performance that comes remarkably close to human touch.”
Moving forward, the researchers say the sensors could be reduced in size even further, potentially shrinking to below 50 micrometres — a scale that approaches the density of mechanoreceptors found in human skin. Future designs may also incorporate temperature and humidity detection, bringing the technology closer to a fully multimodal form of artificial skin.
As robots continue to move beyond controlled factory settings and into homes, hospitals, and other unpredictable real-world environments, improvements in touch sensing could be highly transformative. Such capabilities may enable machines not only to see and perform actions, but also to develop a more refined sense of touch.
A patent application has been submitted through Cambridge Enterprise, the innovation and commercialisation arm of the University of Cambridge. The research received support from the Royal Society, the Henry Royce Institute, and the Advanced Research and Invention Agency. Tawfique Hasan is also a Fellow of Churchill College, Cambridge.
