Enhanced adhesion of bioinspired nanopatterned elastomers via colloidal surface assembly

Abstract

We describe a scalable method to fabricate nanopatterned bioinspired dry adhesives using colloidal lithography. Close-packedmonolayers of polystyrene particles were formed at the air/water interface, on which polydimethylsiloxane (PDMS) was applied. The order of the colloidal monolayer and the immersion depth of the particles were tuned by altering the pH and ionic strength of thewater. Initially, PDMS completelywetted the air/water interface outside the monolayer, thereby compressing the monolayer as in a Langmuir trough; further application of PDMS subsequently covered the colloidal monolayers. PDMS curing and particle extraction resulted in elastomers patterned with nanodimples. Adhesion and friction of these nanopatterned surfaces with varying dimple depth were studied using a spherical probe as a counter-surface. Compared with smooth surfaces, adhesion of nanopatterned surfaceswas enhanced,which is attributed to an energy-dissipatingmechanism during pull-off. All nanopatterned surfaces showed a significant decrease in friction compared with smooth surfaces.