Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces

Significance In transfer printing, robotics, and precision manufacturing, adhesion-controlled grasping of complex 3D surfaces is very challenging because the adhesive must be soft enough to enable intimate contact under light pressure but stiff enough to support high load and fracture strength. We address this dilemma by replacing the adhesive with a pressurized microfiber array that enables independent control of 3D conformability and bond strength. This architecture exhibits enhanced and robust adhesion on various sizes of 3D and deformable surfaces. In contrast to other microfiber adhesives, it has the area scalability of the natural gecko footpad. These features suggest that the proposed soft-gripping system can outperform conventional adhesive systems for a broad range of surface shapes and length scales. For adhering to three-dimensional (3D) surfaces or objects, current adhesion systems are limited by a fundamental trade-off between 3D surface conformability and high adhesion strength. This limitation arises from the need for a soft, mechanically compliant interface, which enables conformability to nonflat and irregularly shaped surfaces but significantly reduces the interfacial fracture strength. In this work, we overcome this trade-off with an adhesion-based soft-gripping system that exhibits enhanced fracture strength without sacrificing conformability to nonplanar 3D surfaces. Composed of a gecko-inspired elastomeric microfibrillar adhesive membrane supported by a pressure-controlled deformable gripper body, the proposed soft-gripping system controls the bonding strength by changing its internal pressure and exploiting the mechanics of interfacial equal load sharing. The soft adhesion system can use up to ∼26% of the maximum adhesion of the fibrillar membrane, which is 14× higher than the adhering membrane without load sharing. Our proposed load-sharing method suggests a paradigm for soft adhesion-based gripping and transfer-printing systems that achieves area scaling similar to that of a natural gecko footpad.

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