Microspine Design for Additive Manufacturing

Microspine grippers allow robots to ascend steep rocky slopes and cliff faces, enabling scientific exploration of exposed strata on Earth and other solar system bodies. Historically, the Shape Deposition Manufacturing (SDM) process has been used to fabricate multi-material suspensions for load-sharing among multiple microspines. We instead apply the Hybrid Deposition Manufacturing (HDM) process to microspine fabrication, and we further propose a novel 3D-printed microspine suspension design that can be manufactured via Fused Deposition Manufacturing (FDM) alone, using a single flexible material with an embedded fishhook. We use a model of microspine stiffness that allows designers to compensate for order-of-magnitude changes in material tensile modulus by adjusting geometric parameters of the design. The stiffness model and the FDM microspine design are validated through tensile testing, and mechanical properties of the HDM and FDM designs are compared against a standard SDM microspine design. We demonstrate that the FDM process can produce microspines with equivalent normal and axial stiffness and superior maximum load and fatigue response to SDM microspines, and discuss additional advantages of the FDM process for rapid prototyping and broader accessibility.

I. Introduction

Climbing robots can advance scientific exploration of our solar system by enabling access to exposed strata found on steep terrain that conventional wheeled rovers cannot reach, such as the cliff faces observed in Jezero and Victoria Craters on Mars, or lava tubes with vent openings on the Martian and lunar surfaces [1]–[4]. Robust, reliable adhesion to vertical or even overhanging surfaces can be achieved through the use of microspines, which use small, sharp hooks to take advantage of millimeter to sub-millimeter scale surface features. Unlike other adhesion mechanisms such as suction, magnetism, or dry adhesion, microspines are well-suited to the rough rock and cliff surfaces commonly encountered during planetary exploration [5]–[7].