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The biologically inspired strategy of distributed inward gripping (DIG) is presented in this study as a method for foot attachment and adhesion during gravity-independent climbing. As observed in nature, this strategy enables climbing animals to maneuver rapidly on surfaces in any orientation with respect to gravity, and does not require significant energy expenditure for attachment or detachment. DIG is an advanced implementation of directional attachment mechanisms that directs contralateral legs to engage their cockroach-inspired prehensile spines by pulling inward toward the body, rather than downward opposing gravity. By using opposing foot forces to engage the spines, the dependency on gravity is removed and the experimental system designed to test the attachment strategy, DIGbot, is able to climb and make turns on both vertical and inverted mesh screen. This behavior has not been achieved previously by a legged system, and requires novel design and algorithmic features that will be discussed. The spacing in the mesh screen requires each foot to perform a local search for an adequate foothold, which mimics what has been observed in climbing insects. The inward gripping principle is also suited for use with microspine arrays and gecko-inspired dry adhesive pads that require pulling tangential to the surface for attachment, and ultimately will allow for rapid and complex maneuvers on irregular terrain.
Palmer et al. (Wed,) studied this question.