Study on Micro and Nanostructured Surface for Enhancement of Adhesion Performance

Abstract

The bonding performance in the junction of different materials is largely determined by the interaction between the materials at the interface and the surface topography, which are the two key factors. Since the interaction between materials is a measure of the chemical bonding, it is difficult to expect performance improvement without changing the materials. In contrast, the surface topography can easily enhance or diminish bonding performance depending on the processing method. The surface topography can be controlled through roughness, and the effect of roughness on bonding performance varies significantly depending on the level of roughness. In this study, the bonding performance was compared based on surfaces with micro and nanometer-level roughness. Firstly, in a situation where the interaction between materials at the surface is minimal, bonding was achieved through simple application of roughness for physical bonding. Recent research has been actively conducted to replace parts of systems with high-strength plastics for weight reduction. In line with this trend, research on increasing the bonding strength of joints connecting plastic and metal materials to enhance the overall system robustness has been actively pursued. Particularly, research on insert molding as a replacement for conventional bonding methods and direct bonding based on the generation of metal microstructures has emerged as new approaches. In this paper, we developed a novel method for direct bonding of metal-polymer using organic solvents without the need for thermal management. By creating microstructures and nanostructures on aluminum and dissolving only the surface of aluminum butadiene styrene (ABS) using chloroform, we confirmed that the polymer infiltrated between the structures, completing the bonding. The changes in bonding strength were observed through simple shear tests and T-peel tests for each structure. The shear strength was found to be equivalent to the sum of the strength values of micro and nano single structures when the composite structure had varying surface heights. The peel strength significantly increased in the case of the composite structure due to the additional shearing force. Secondly, in the context of bonding in dental implants, various types of surfaces were applied to compare cell growth on the surfaces. Titanium, the main material in dental implants, undergoes osseointegration with dental bone cells through chemical bonding, so the bonding performance with teeth is closely related to cell differentiation on the surface. In this study, we investigated osseointegration performance by increasing surface roughness through the formation of microstructures and nanostructures on the surface. The Cell Counting Kit-8 (CCK-8) assay analysis was used to confirm osseointegration on the surface. The microstructure was fabricated by chemical etching using sulfuric acid, and the nanostructure was fabricated by dipping in a sodium hydroxide solution. The microstructured surface showed increased initial cell adhesion, but no increase was observed on the nanostructured and micro/nano hierarchical surface. However, the surface with nanostructures showed increased cell proliferation after 14 days, while the microstructured surface showed a significantly decreased proliferation rate. The micro/nano dual-scale structure exhibited the highest increase in proliferation rate. Thus, it was confirmed that the dual-scale surface structure, composed of structures of different sizes rather than a single structure, significantly enhanced bonding performance.