Surface buckling enabled soft clutch†

Abstract

Geckos in nature can shed their tails via autotomy to distract predators and escape, while soft robotics, despite its flexibility, lacks detachable and reconfigurable components. This work introduces a surface buckling enabled soft clutch that achieves bidirectional (normal and tangential) engagement through geometric interlocking of pre-programmed inverted trapezoidal waveforms on stretchable substrates. The clutch design leverages compressive stress-driven buckling of thin films to create reversible morphological transitions. Experimental results demonstrate that the soft clutch achieves stable tensile and shear strengths. Reduced angle between the film legs and the substrate and increased film thickness improve mechanical performance of the soft clutch. Theoretical models incorporating film buckling and geometric constraints accurately predict tensile and detachment strengths. A bio-inspired gecko robot with a clutch-connected detachable tail validated the clutch's utility: under simulated predation, pneumatic actuation enabled tail autotomy, ensuring escape of the body part.