Robots can now “see” touch thanks to a new colour-changing tactile sensor

The novel idea was invented by Giacomo Sasso, a postdoctoral researcher at the School of Engineering and Materials Science at Queen Mary University of London, and it works by transforming invisible forces into dynamic colour patterns. This enables high-resolution maps to contact, strain and pressure to emerge instantly. When pressure is applied to a soft sensing surface, the material produces spatially varying structural colours that can be captured immediately using a standard camera, removing the need for complex reconstruction algorithms. 

This technology enables the development of a robotic gripper assembling micro-scale components with the delicacy required in precision manufacturing, where every subtle variation in force becomes visible in real time. It can make a concurrent impact in healthcare where an external prosthetic (artificial limb) can get a richer sense of touch during delicate daily or clinical tasks. Simultaneously, it can allow surgical systems to distinguish healthy from abnormal tissue by reading fine pressure signatures directly through the material’s colour response. 

Unlike traditional tactile sensors, the new system embeds sensing directly into the material itself. Mechanical interactions are transformed into colour fields that a low-cost USB camera can read in real time. The challenging task has already obtained results showcasing the first real-time solution in the field. 

“You won’t guess how much information is generated when your finger presses a light switch. A human hand contains more than 10,000 mechanoreceptors to do the job, yet touch sensing remains one of the major challenges in robotics. We were happy to capture the finger ridges, as no existing technology can reproduce such sensor density at comparable scale and simplicity. The key idea behind this project was to think outside the box: instead of embedding dense and overengineered sensor arrays, sensing is moved into the material itself, where mechanical cues are directly transformed into colour fields and captured using a simple low-cost USB camera” says Giacomo Sasso. This produces rich pressure maps while simplifying the system architecture. 

Co-authors on this project from the University of Florence, University of Trieste and University of Trento in Italy agree that “What is particularly powerful is that the information is already in the light signal. You are no longer reconstructing touch - you are observing it directly.” says Professor James Bustfield. 

The idea emerged from the need to overcome a persistent trade-off in vision-based tactile sensing: high-resolution systems typically require heavy computational pipelines to reconstruct contact geometry, introducing latency, while faster systems often sacrifice spatial detail. 

The strong collaboration between Professor Federico Carpi, from the University of Florence and Professor Busfield, merges two research worlds of soft robotics and material science. Building on years of work on stretchable sensors and polymer characterisation, the team has progressively advanced the ability to interface mechanical compliance with functional sensing. Within this framework, mechanochromic materials represent a new direction: instead of relying on highly engineered microelectronics to interpret deformation (taxels), the material itself becomes the sensing medium, directly encoding mechanical interaction into visible optical signals.

You can read the full paper on the American Association for the Advancement of Science.