Investigating the effects of solution viscosity on the stability and success rate of SECCM imaging

Due to the capability of simultaneously detecting the morphology and electrochemical information of samples and limiting the electrochemical reaction to a range approximately the size of the inner diameter of the pipette tip opening, scanning electrochemical cell microscopy (SECCM) enables higher precision local electrochemical measurement and surface material delivery and has been demonstrating unique advantages and broad application prospects. However, the meniscus droplet at the pipette tip of SECCM is equivalent to the opening radius of the pipette tip, which is usually tens of nanometers to hundreds of nanometers. The tiny meniscus droplet makes it susceptible to evaporation and crystallization, which increases the likelihood of the pipette colliding with the sample during the scanning process, resulting in the failure of scanning. In this paper, the influence of solution viscosity on the shape variation of the droplet at the tip during the movement of the pipette of SECCM was studied by finite element analysis. It is proved that the increase of solution viscosity is helpful in reducing the shape variation of the droplet at the tip during the movement of the pipette. Then scanning experiments were carried out using a flat Au substrate and Au substrates with rounded triangle and rounded rectangular convex structures as the samples. According to the experimental results, increasing solution viscosity improves scanning success rates and scanning quality and effectively lowers the MSE of the scanning results. The experimental results also show that SECCM can image at a higher speed when the solution's viscosity increases since the deformation of the droplet at the tip is less than with a typical solution.