Monolithic 6-Axis Force/Torque Sensing by a Single Ultrathin Piezoceramic Shell

Miniature multi-axis force/torque sensors are essential for advanced robotics and wearable devices, yet their development is hindered by complex multi-beam structures and laborious calibration. We overcome this by introducing a monolithic 6-axis force/torque sensor constructed from a single, ultrathin-walled piezoceramic shell. This architecture eliminates the need for multi-component assembly and algorithm-driven decoupling, relying instead on the intrinsic mechanical deformation modes of the engineered shell for direct and reliable dynamic force/torque variation measurement. Leveraging this architecture, our sensor enables straightforward calibration and achieves a decoupling accuracy of 99.37% across 120,000 randomized dynamic tests. We fabricated the core sensing element as a 50-μm-thick annular piezoceramic shell to maximize sensitivity and limit of detection, achieving detection limits better than 3 mN in normal force, 4 mN in tangential force, and 0.3 mN·m in torque. We demonstrate a compact, 3.85-gram sensor (2.53 cm³) that integrates seamlessly into robotic grippers for event-driven delicate assembly and into exoskeletons for high-fidelity dynamic monitoring of in-home rehabilitation. This work establishes an architecture for inherently decoupled force/torque sensing, with broad potential in advanced robotics, prosthetics, and personalized medicine.