New soft sensor can turn touch into robotic action without electronics

NUS researchers have developed ME-SOFS, a 3D-printed mechanical soft force sensor designed to connect touch directly to robotic movement without computers, powered electronics, or external energy. The device is made from a compliant porous structure with a central pillar and five fluid-filled chambers: four horizontal and one vertical. Force makes the pillar tilt, compressing selected chambers and pushing fluid through soft tubing to remote actuators. Because the chambers act independently, the system separates horizontal, lateral, and vertical forces while converting them directly into fluidic actuation.

The design can also yield an electrical readout without powered electronics. Fluid displacement moves magnets past 3D-printed metal arcs, inducing voltage pulses; pulse numbers correspond to applied-force magnitude. Sensitivity can be adjusted by changing 3D-printing geometry, including hole diameter, slope thickness, and slope angle.

In demonstrations, researchers printed a five-sensor glove as one continuous single-material piece without manual assembly. The pea-sized fingertip sensors detected grasping forces and predicted object weight. In another test, fluid pressure from a robot gripper was transmitted to a fingertip haptic pad worn by a blindfolded operator, enabling touch-based control while grasping items including an egg, wooden blocks, and a half-filled water bottle. Recorded successful-grasp signals were replayed to train the robot to reproduce motions autonomously.

ME-SOFS also guided liquid droplets in a miniature fluid controller and bent hair-like flexible structures according to force direction and strength. It remained stable in 90°C water and at pressure equivalent to roughly 11 meters of depth. Its open fluid channels equalize ambient water pressure, and its electronics-free construction avoids electromagnetic interference.