Bioinspired Crown Cutter—The Impact of Tooth Quantity and Bevel Type on Tissue Deformation, Penetration Forces, and Tooth Collapsibility

Abstract

Current keyhole biopsy devices are rather ungainly, inaccurate, and limited in application. A keyhole biopsy harvester was designed to facilitate peripheral cancerous tissue detection and resection at high speed and accuracy. The harvester's cutting tool, the crowncutter, was bioinspired by the sea urchin's chewing organ—Aristotle's lantern. This paper focuses on the optimization of the crowncutter with regard to the impact of different tooth quantity and bevel type on tissue deformation, penetration forces, and tooth collapsibility. Two sets of crowncutter designs were manufactured and tested in pushin experiments using gelatin—the first set having no bevel and differing tooth quantity (4, 6, 8, 10 teeth) and the second set of constant tooth quantity and differing bevel type (no, inner, outer, and inner and outer bevel). The gelatin surface deformation and the penetration forces were evaluated utilizing a high speed camera and a universal testing machine, respectively. The experimental results on the crowncutters of different tooth quantity (no bevel) showed a steady increase in the tissue deformation with the increasing amount of teeth. Unlike the bevel type, the different tooth quantity revealed significant differences with regard to the tissue deformation in between 4 versus 6teeth and 10 versus 6teeth cutters. As for the penetration forces, the significant difference was found only between 10 and 6teeth cutters. In conclusion, reducing the cutter's tooth quantity resulted in lower tissue deformation, whereas differing the bevel type was found to have a negligible influence. Ultimately, a high ratio of outward to inward tooth collapsibility and a relatively low inner moment of inertia proved the 6teeth cutter to be the most optimal.