Mechanical multiaxis force sensor for directly bridging sensing and fluidic actuation

Robots are the intelligent systems that connect sensors and actuators. Many sensorimotor architectures use close-loop control codes that arbitrate sensing signals, entailing processing modules. Reactive architectures minimize computational demands by establishing direct sensor-actuator connections and have proven to be effective and robust. Here, we introduce a mechanical analogy of such reactive systems: a fluidic-based multiaxis mechanical soft force sensor (ME-SOFS) that directly couples sensory signals with fluidic actuation, eliminating the need for external computation or energy input. The ME-SOFS can be easily reconfigured and integrated to endow robots with somatosensory multiaxis force sensing capabilities. Based on fluid transduction, ME-SOFS converts applied force into mechanical output for fluidic actuators. We demonstrate this sensing-actuation loop in three scenarios: directional droplet manipulation, unified bending of cilia-like array guided by detected force vectors, and haptic feedback system that accelerates robotic grasping learning. ME-SOFSs demonstrate how fluidic approach can realize multiaxis force sensing for soft robots, and enable simplified, closed sensing-actuation loops and haptic human-machine interfaces.