Ridged Zn/PDMS smart surface with wide-range reversible wettability and high sensitivity responsive to mechanical strain

Smart surfaces with dynamically tunable wettability place an important role in microfluidics, biomedical engineering and flexible electronics. Mechanical strain is a promising stimulus to tune the surface wettability, how ever, it is still a great challenge to achieve both wide-range reversible wettability and high sensitivity. In this study, highly ordered and quasi-periodic ridge patterns with cracks at their peaks were tailored based on a film-substrate system by sputter deposition of zinc (Zn) nanofilm on prestretched polydimethylsiloxane (PDMS). The contact angle (CA) on the ridged Zn/PDMS surface is well tunable between 115 degrees and 143 degrees by adjusting the applied strains. It is remarkable that such a structure possesses wide-range CA variation (-28 degrees) under just 28.6% applied strain, indicating a high responsive sensitivity (eta = 98 degrees). This result is attributed to the cracked ridges with both wide-range aspect ratios from 0.07 to 0.54 and high rate of change (-1.70). More over, the responsive reversibility of the ridged Zn/PDMS surface remains up to 1000 cycles and 60 days without special protection. The outstanding performances make the ridged surface could be a promising component for various technological applications, especially in small strain required situations. (c) 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).