Climbing animal's feet use combinations of interlocking and bonding mechanisms in a staggering array of designs. The most successful climbers' feet exhibit a complex hierarchy of varied mechanical structures at multiple scales, combining small appendages that generate shear or adhesive forces with compliant suspension systems that promote intimate contact with surfaces. Recent progress is presented in mechanical and materials design that integrates novel dry adhesive and microspine structures mounted on passively compliant suspensions into successively improved generations of feet targeted at the RiSE (Robots in Scansorial Environments) family of climbing robots. The current version can ascend 90° carpeted, cork covered and a growing range of stucco surfaces in the quasi-static regime. Specifications of a "public interface" for integrating a broad range of synthetic appendages into the foot assemblies are presented in the hopes of encouraging as large as possible a community of MEMs and Nanomaterials designers to submit adhesive or friction enhancing materials for operational tests using the robot.
We review a large multidisciplinary effort to develop a family of autonomous robots capable of rapid, agile maneuvers in and around natural and artificial vertical terrains such as walls, cliffs, caves, trees and rubble. Our robot designs are inspired by (but not direct copies of) biological climbers such as cockroaches, geckos, and squirrels. We are incorporating advanced materials (e.g., synthetic gecko hairs) into these designs and fabricating them using state of the art rapid prototyping techniques (e.g., shape deposition manufacturing) that permit multiple iterations of design and testing with an effective integration path for the novel materials and components. We are developing novel motion control techniques to support dexterous climbing behaviors that are inspired by neuroethological studies of animals and descended from earlier frameworks that have proven analytically tractable and empirically sound. Our near term behavioral targets call for vertical climbing on soft (e.g., bark) or rough surfaces and for ascents on smooth, hard steep inclines (e.g., 60 degree slopes on metal or glass sheets) at one body length per second.