Frictional characteristics of stiff, high aspect ratio microfiber arrays based on cyclic olefin polymers

Cyclic olefin polymer (COP) microfiber arrays with diameters in the range of 0.6–5 μm and up to ~20 μm in length are successfully fabricated using polycarbonate membranes as templates, and their macroscale friction properties are evaluated against smooth glass surfaces. Increasing the aspect ratio of the fibers decreases the effective modulus and increases the effective work of adhesion, which favor a better compliance, resulting in higher friction forces. On the other hand, the shape of the fibers as well as inter-fiber adhesion at high aspect ratio complicates the dependence of friction on fiber geometry. Among the arrays investigated, the 2 and 0.6 μm diameter arrays exhibited excellent friction performance (up to ~6 and 9 N/cm2, respectively) and high fractional contact area (50–60%). These results suggest that arrays with high friction properties can be easily obtained by molding COPs from polycarbonate membranes.