Evaluation of Material Properties for Practical Microstructured Adhesives: Low Dust Adhesion and High Shear Strength.

The development of microstructure (gecko-like) adhesives has focused almost solely on their adhesive strength. However, for practical applications, especially in real-world environments, the adhesive's long-term performance is arguably equally important. One impediment to long-term viability is the adhesive's susceptibility to contamination. It is a challenge to develop an adhesive that can both adhere to a substrate while not becoming contaminated with dust and debris. In response, this paper experimentally explores the effect of modulus of elasticity, work of separation, and work of adhesion (adhesion energy) on the shear stress and particle detachment capabilities of wedge-shaped, directional microstructured adhesives. Particle removal is evaluated using both noncontact cleaning methods (centripetal force and electrostatic particle repulsion) and a dry contact cleaning method (load-drag-unload test). Results show that for a material with a high work of separation, high elastic modulus, and low work of adhesion, it is possible to create a microstructured adhesive with both high shear stress strength and low adhesion to dust particles. Results also show that, for dry contact cleaning, shear stress recovery mostly stems from particle rolling and not particle sliding. Moreover, shear test results show that augmenting the microstructured adhesive with electrostatic adhesion can reduce the negative effects on adhesion of a high elastic modulus materials' conformability to a substrate by providing a preload to the microstructured elements. Last, this paper is the first to report on a electrostatic/gecko-like adhesive that uses its electrostatic elements for both adhesion and dust repulsion; they were reported separately before.