Ovipositor-inspired needle insertion without a net push force

Abstract

Abstract—As current rigid needles follow straight line trajectories, limiting the path planning possibilities in minimally invasive surgical approaches, research into steerable needle instruments becomes necessary. This article outlines the development of a four-part needle prototype inspired by the ovipositor of parasitic wasps and designed to penetrate without a net push force. In the wasp ovipositor, three valves move reciprocally to gain depth in the substrate with one valve at a time, while the other two valves anchor against the substrate and provide lateral support. The needle prototype consists of four reciprocally moving needle parts, devoid of any tissue gripping textures, with a combined cross-section of 2 x 2 mm, supported by a platform which is able to move with low friction. The goal of this study is to penetrate tissue phantom material without applying a net push force by using a friction difference induced between protruding needle parts and stationary needle parts, solely based on the difference in the size of surface area subjected to needle-tissue friction. The prototypes validation in gelatin phantom shows needle insertion with limited push force, independent from the penetration depth. The performance of the prototype is measured by the amount of slip between needle and substrate. Slip shows to be proportional with needle-part offset and inversely proportional with gelatin concentration, whereas protrusion sequence and needle-part velocity seem to have little effect on performance. Validation of these relations is found challenging due to the effect of inertia and bearing friction on the measured slip.