The Effect of Integrating a Bio-Inspired Convex Structure with a Low-Surface Energy Polymer on Soil Adhesion and Friction

The capacity of soil-burrowing animals to move freely in sticky soil is a motivational trait for developing soil engaging tools with high operational efficiency. The hydrophobicity and morphological profiles of soil animals' skin were reported to be the key pillars in producing their anti-adhesive mechanisms. Ultra-high molecular weight polyethylene (UHMW-PE) possess outstanding corrosion resistance, hydrophobicity, and chemical stability, which qualify it as a potential choice in soil adhesion reduction. Hence, this study aimed to investigate the feasibility of integrating a domed surface inspired by the micro-convex structure of the dung beetle skin with the UHMW-PE as a surface coating for soil engaging components in terms of soil adhesion reduction. The sliding resistance of three sliding plates (flat plate of carbon steel, flat plate of UHMW-PE, and domed plate of UHMW-PE), entirely identical in the projected area, was evaluated in two soil textures of silty clay and sandy clay loam, at four moisture levels of 18, 23, 28, and 33% and four drag speeds of 0.15, 0.2, 0.25, and 0.3 m s-1 using a completely randomized design. The dimensions of the embossed domes on the tested plate surface and their distribution pattern were established based on the previously published structural optimization of the bioinspired convex surface. In each treatment, the tested plate was dragged for 0.7 m of the soil bin length, and the sliding resistance was recorded continuously using the distributed stress and strain test and analysis system (DH3820 N). The coefficients of adhesion and friction were calculated according to the Mohr-Coulomb failure criterion. The variance analysis revealed that all investigated parameters significantly affected coefficients of adhesion and friction. In addition, as compared to flat steel plates, UHMW-PE coated plates exhibited much lower adhesion in all treatments, paving the way for practical applications in soil adhesion reduction and soilengaging component optimization.