Barbed Mirconeedle Design to Enhance Penetration and Retraction Forces using Finite Element Modelling

Nature has optimized the structure of needles to reduce penetration force and increase retraction force as demonstrated by honeybee stingers, mosquitos and porcupines. Current microneedles typically consist of smooth sharp tips to reduce penetration forces, but these have poor retraction forces. This paper investigates the design of a bio-inspired barbed microneedle and its effects on insertion and retraction forces on the outer and inner layers of the skin. Various microneedle designs were investigated using COMSOL Multiphysics software to determine the impact of needle tip sharpness and barbed design on the forces. The interlocking of the microneedle with skin tissue was higher in the case of barbed-shaped microneedle compared to barbless needle resulting in a higher retraction force. Also, the size and geometry of the microneedle design affect the insertion and retraction forces characteristics. The development of a finite element model will allow us to further enhance the design of bio-inspired microneedles. This work also demonstrates the feasibility of using microfabrication techniques to manufacture various barbed microneedle designs using Su-8 based microneedles.