Design, fabrication and characterization of gecko inspired micro-fibrillar adhesive materials for wall climbing robots

Advancement in adhesion technology has improved the development of wall-climbing robots. But there are still some challenges in the optimization of high adhesion strength bioinspired adhesives. Most of the traditional wall-climbing robot feet use vacuum suction and magnetic suction, which require smooth contact surfaces and magnetic permeability respectively, and their application scenarios are greatly limited. Therefore, new biomimetic adsorption methods need to be developed. Adhesives in air, inspired by geckos and spiders and other climbing animals in nature, adhere to the opposite surfaces using van der Waals forces. The biofiber-dried adhesives have a tree-like hierarchy: on the surface of the animal’s foot has a thin film of arrays of microfibers, each is divided into smaller arrays of submicron fibers. These nanosized fibril can bind tightly to opposite surfaces to induce van der Waals interactions. The van der Waals forces cause these nanosized fibril arrays to bind tightly to surfaces. Bionic studies based on gecko and spider adhesion mechanism has become a fierce research subject in the past few years. Previous studies have confirmed that finer contact structures produce higher adhesion. The influence of tip shape on the performance of adhesives of single fiber and fiber array is also a focus of research. In this work, in order to enhance the adhesion of biomimetic materials, patterned surfaces with micro-columns with different tip shapes are prepared by lithography and micromolding methods. We measured their normal adhesion and compared with flat contact surface. Micro pattern surface was found to be better than flat surface smooth. Different shape has a significant effect on adhesive force. A prestressing force of adhesive force and dependency has been identified and that is a key to obtain the adhesion force, which can provide the possibility to expand the application scenarios of wall-climbing robots and exists many potential applications from wall-climbing robots to bionic patches.