Statistical Characterization of Biomimetic Gecko Adhesives

Abstract

This paper presents a way to characterize the strength of bioinspired gecko-adhesives. These are the most promising mechanisms, so far, which enable controlled adhesion (i.e. turning it on and off). They emulate the forces present in geckos’ fingertips to stick temporarily to surfaces without any preconditioning and keeping them intact. Moreover, they do not need of any specific environment to work, which makes them specially useful for space applications such as grippers, or robots capable of climbing the outer surface of a space vehicle to perform inspections or repairs. To further enhance their adhesion strength, a high voltage electrostatic field is usually applied. However, while these adhesives tend to perform very well on smooth surfaces, the nefarious effects of surface roughness are yet uncharacterized. In this paper, we developed a statistical method to characterize those effects based on the concept of effective surface defects, and without need of a yet intractable direct measurement. In particular, controlled surface defects on adhesives themselves were statistically analyzed through a sample of over 2000 experiments; matching them with the statistical results. Through this process, the validity of the analysis lead to a way of calculating effective surface defects on substrates by considering the dual problem. Because this method does not require substrates to have any specific surface conditions, its use might be extended to study adhesion on more challenging surface morphologies such as that of kapton thermal covers, which often appear on space vehicles.