Research on Surface Mechanical Properties of Polydimethylsiloxane Stamp Microstructures in Self-diffusion Process

In micro-contact printing, the structural stability and shape accuracy of the elastomeric stamp are critical for structural printing with high resolution and precision. When printing alkanethiols on gold surfaces, the self-diffusion phenomenon of organic solvents occurring in the micro-nano pores inside polydimethylsiloxane (PDMS) during the ink dipping process tends to change the mechanical properties and geometry of the stamp, thus affecting the accuracy and effectiveness of the printed patterns. In order to investigate the effect of this self-diffusion phenomenon on the microstructure of the PDMS stamp surface, PDMS stamps with microstructure patterns of different aspect ratios were prepared by casting off on a lithographic silicon wafer template. PDMS stamps with different HDT mass fractions were prepared by immersing the PDMS stamps in 1-hexadecanethiol (HDT) and by controlling the time of self-diffusion of HDT inside PDMS, and based on optical microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements, the effects of the self-diffusion process on the structural stability of the stamp microstructures, surface adhesion and the shape accuracy of the patterns. The results show that the self-diffusion of HDT causes a decrease in both the modulus and adhesion of the PDMS stamped microstructure, and the structural stability of the microstructure with an aspect ratio of 1:1 is relatively best. Secondly, the longer the time of self-diffusion, the higher the content of HDT inside the PDMS, the greater the decrease in the modulus and adhesion of the microstructure, and the higher the shape expansion of its pattern. In addition, the effect of curing agent content on the Young's modulus and adhesion force of PDMS stamp microstructures was investigated by varying the ratio of prepolymer to curing agent. The results can be used as a reference basis for the preparation of PDMS elastic stamps with high structural stability and printing accuracy. [Graphics] .