Gentle Grasping With Gecko-Inspired Adhesives in Extreme Environments

With the ultimate goal of gently attaching to smooth surfaces in space using gecko-inspired adhesives, we conducted tests with suspended adhesive tiles and a gripper in a low-temperature chamber. In comparison to previous stiff, displacement-controlled tests, these experiments approximate the kinematically unconstrained, force-controlled contact and engagement with objects that will occur in orbit. We show that the elastic behavior of the adhesive’s anisotropic microstructure at first contact is affected by temperatures below a characteristic temperature. For the anisotropic Sylgard 170 adhesive tested in this work, the lower temperature of engagement failure was found to be $- 60~^{\circ }$ C. Accordingly, a suspended gripper with two adhesive tiles was able to engage and lift a test plate at an ambient temperature of $- 47~^{\circ }$ C. At lower temperatures, a solution is to briefly heat the adhesive tiles just prior to contact. We show that there is a correlation between adherend surface temperature and the required heating for attachment, and that preload pressure has a large impact on adhesive performance when engaging with adherend surfaces below the critical failure temperature. Once the adhesive has engaged, the heat can be turned off without reducing adhesive strength. We conclude with recommendations for future work aimed at increasing the reliability of gentle attachment to objects in orbit.