Direct micropatterning on a titanium surface through electrochemical imprint lithography with a polymer electrolyte membrane stamp

Abstract

Fabrication of surface microstructures for Ti and its alloys, which can enhance the physical and chemical properties of Ti surfaces such as the corrosion resistance, wear resistance, and biocompatibility, have been extensively examined. Anodic oxidation can effectively functionalize Ti surfaces by producing an oxidation layer or nano/microstructure on the Ti surface through a simple setup. However, a considerable amount of liquid electrolyte is used, which necessitates post-process cleaning and liquid waste treatment, thereby incurring time and monetary costs. To avoid this problem, we establish a direct electrochemical imprint lithography to produce micropatterns on Ti surfaces without using a liquid electrolyte. Specifically, a polymer electrolyte membrane (PEM) stamp that contains the pattern on its surface is used to replace the liquid electrolyte. Therefore, no harsh chemicals are required in the electrolysis process that involves a Ti (anode)/PEM/cathode electrochemical system. Different patterns such as dots, honeycombs, and mesh structures can be directly formed on the polished Ti surface by using the PEM stamp prepared via solution casting. Scanning electron microscopy and energy dispersive X-ray spectroscopy analyses indicate that the Ti surface in contact with the PEM stamp is selectively oxidized to form the pattern structure. A line and space (L&S) structure with a height of several tens of nanometers and vertical resolution of ~1 μm is prepared. The L&S-structured Ti surface exhibits a larger contact angle toward water than that of the untreated Ti surface. Multiple-pattern formation with a single L&S PEM stamp is demonstrated to form complex microstructures on the Ti surface. The proposed electrochemical treatment, which can produce micropatterns on Ti surfaces through a simple procedure that does not employ masks and harsh chemicals, is an environmentally friendly and cost-effective approach to functionalize Ti-based materials.