In order to improve crawling efficiency, we started to develop controllable grippers for the caterpillar robot. There are three common mechanisms for gripping: Hooking, Adhesion, and Suction. For the scale of our robot, micro-hooks array and adhesion pads seemed most probable. Manduca caterpillars use the former(crochets) while most insects employ both. However, there are great challenges in both systems.
To effectively dig into substrate of non-uniform stiffness, the micro-hooks array has to vary in hook size and compliance. Up to date, we have very little knowledge about these hooks arrangement and properties. Let alone the task of manufacturing such an micro-array for load bearing.
On the other hand, sticky pads are easier to produce. There are hundreds if not thousands of different adhesive materials to choose from. However, release of sticky pads may be quite a challenge for small robots.
After evaluating the situation, I decided to design a membrane with sticky substance on it. Once I master how to control such a membrane, I could control the sticky pads. Then, micro-hooks array can be incorporated into the system.