Researchers have developed an innovative soft tactile unit, known as the F3T sensor, capable of mathematically decoupling three-dimensional (3D) force and temperature measurements. This is a major step forward in robotic tactile sensing.
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While human skin naturally distinguishes between contact forces and environmental temperatures, current soft tactile sensors often struggle to separate these signals accurately, limiting their use in more complex robotic tasks. The F3T sensor addresses this challenge with a design inspired by the layered structure of human skin, integrating multiple materials and sensing mechanisms across four layers.
At the top is an ion gel-based film that senses temperature. As temperature shifts, the spacing between polymer chains in the gel changes, altering electrical resistance and allowing for precise, independent temperature detection.
Below that, a circular coaxial magnetic film combined with a floating multilayer capacitor physically separates normal and tangential forces in all directions. The third layer—another floating capacitor—responds only to normal force, effectively filtering out tangential input. The base layer is a rigid PCB responsible for structural support and signal processing. An internal silicone elastomer mimics the skin’s hypodermis, cushioning impacts and holding components together.
Together, these layers allow the F3T sensor to accurately distinguish between temperature, normal force, and multidirectional tangential force. When the sensor makes contact with an object, the composite signal it receives is processed in stages: the ion gel decouples and reads the temperature first, followed by the floating capacitor and magnetic film, which isolate and measure the normal and tangential forces, respectively.
Performance testing shows promising results. The sensor’s temperature readings remain stable even under varying external forces, and its force measurements—both normal and tangential—are highly accurate. It also responds quickly to dynamic changes.
In both static and dynamic tests, the F3T sensor outperformed traditional alternatives. In static scenarios, it measured 3D force and temperature with minimal error. During dynamic testing, a robotic gripper equipped with the sensor was able to adapt to external disturbances and maintain a stable grasp.
The sensor also proved effective in real-world applications. During an automated chemical reaction process, it helped maintain precise control over heating and shaking. In a “tea delivery” human-robot interaction task, it enabled the robot to detect human intent and smoothly transfer the cup.
While the F3T sensor shows strong potential, there’s still room for improvement, particularly in enhancing inter-layer adhesion, ensuring consistency in performance, and minimizing delays in temperature readings. Still, its current capabilities suggest it could enable more adaptable and responsive robotic systems across a range of tasks.
Journal Reference:
Yang, X., et al. (2025) A Soft Tactile Unit with Three-Dimensional Force and Temperature Mathematical Decoupling Ability for Robots. Engineering. doi.org/10.1016/j.eng.2025.02.008.