Biomimetic Anti-adhesive Surface Of Minimally-invasive Electrosurgical Electrode

High-frequency electrotome is the most common energy-carry minimallyinvasive surgical instruments. It contact and heat the body tissue by thehigh-frequency and high-voltage current through the electrode tip， to achieve theseparation and solidification of body tissues， and thus play a cutting and hemostasispurposes. However， the working electrode temperature is too high in operation，so leading the biopsy to pyrolysis， carbonization to eschar and sticking to the knifesurface， impacting the effect of operation or cause tissue tearing. Traditionalmethods for anti-sticking on electrodes rely on simple coating technology or edgeshape optimization technology， which is difficult to satisfy the requirements ofminimally invasive medical devices. Therefore， this paper considers on bionicdesigning and manufacturing on electrode surface， according to the outstandinganti-adhesion characteristics of typical plant leaf surface.This paper selected folium perillae and corn husk for biology model for surfacecharacterization. Folium perillae had the surface compactly pieced together byjigsaw-like plates， with stomas embedded. Corn husk had the surface appearedlongitudinal undulated ripples with grids and surface wax on， and had grains onsecondary microscale. Folium perillae and corn husk showed hydrophilicity andhydrophilicity respectively. The small-to-large order of leaf surface adhesion was：fresh corn husk<heated corn husk<fresh folium perillae<heated folium perillae.Namely， corn husk had better surface desorption than folium perillae and fresh leafwas superior to heated leaf. Therefore， fresh corn husk had good performance fordesorption and hydrophobic properties， so optimized as the biology prototype forhydrophobic， anti-sticking and surface desorption.Using natural fresh corn husk as template and twice-reproduce method，obtained a bionic PDMS template surface with microstructure of corn husk， whichcould successfully replicate plant leaf’s real surface morphology on micron level.PDMS templates with positive and negative structure of corn husk had significantlyincreased contact angle compared with smooth PDMS， indicating that the surface micro structure of corn husk has a positive effect for materials hydrophobicity.Established solid modeling of surface morphology on corn husk with ANSYS, and made steady-state heat transfer analysis. Studies have shown that:when the lower surface was heated, the temperature distribution on upper surface was non-uniform due to the morphology. The temperature on upper surface of wide stripes was higher than narrow stripes, indicating that heat current transferred more through wide stripes than narrow ones. The temperature in gap hollows was higher than the stripes’top, showing that temperature decrease less when heat flowed to the gap than to the top. Moreover, surface morphology would extend the surface area, helpful to heat dissipation.This paper analysized some factors of corn husk on the anti-adhesion and desorption of its surface, of the influence mechanism.Corn husk’s big contact angle and poor wettability, surface composite nonsmooth morphology, stress concentration and thermal stress, air exist in surface and internal structure, all weakened the interface adhesion.Designed the surface bionic morphology of the electrode with circle and stripe alternatively distributed, and carved the morphology with the method of laser engraving. Simulated the electric resection operation with energy-carrying, and studied the relationship between adhesive mass and morphology on electrode. The optimal combination through range analysis was z11z22z33,and factors influence order was z2> z3> z1. Established the regression equation about adhesive mass and geometry parameters through regression analysis was y=5.9325+0.032z1-0.0251z2+0.0038z3.Carried out experiments and analyzed thermal effects of different power and cutting time to tissue. The adhesion mass decreased in16-64W of the electrical power and1-6s of the cuting time. When electric power was too low or the time was too short, the accumulated heat by the current could not reach denaturation temperature of the organization. When the temperature was to a certain extent, the organization dehydrated and cured. In addition, when the temperature was too high, tissue started charring.