Contact-mechanical studies on adhesion of bio-inspired elastomeric nanofiber to stiff and soft materials

The adhesion behavior of elastomeric nanofibers was examined by a contact-mechanical approach using a Johnson–Kendall–Roberts (JKR) instrument. A nanofibrillar elastomer substrate was fabricated by replicating crosslinked polydimethylsiloxane (PDMS) from an anodic aluminum oxide (AAO) template. The adhesion behavior of a regular hexagonal array of PDMS nanofibers formed over a wide range was investigated using soft and stiff hemispherical probes, which were prepared using PDMS and polystyrene (PS), respectively. The intrinsic work of adhesion (W) of the elastomeric nanofibrillar substrate was observed to substantially decrease, which was more prominent for the less deformable PS probe, revealing a reduction in the real contact area. Meanwhile, the adhesion energy (G) in the dynamic state with increasing separation rate was greatly affected by the deformation of nanofibers. The energy-dissipation factor for the nanofibrillar surface was far larger than that for the flat surface, and this difference was more significant for the case of contact with the deformable PDMS probe. This resulted in a great increase in the adhesion energy, making it even larger than that of the flat surface, overcoming the reduction in the real contact area