Towards the use of mushroom-capped dry adhesives in outer space: Effects of low pressure and temperature on adhesion strength

Instrumented indentation apparatus and techniques were applied to the testing of synthetic gecko adhesives in an attempt to characterise their ability to function in a space environment. The indentation apparatus was capable of operating at reduced pressures, allowing a higher vacuum level ( 1 × 10 − 5 mbar ) than dry adhesives have previously been tested under. Using a 1.5 mm spherical quartz indenter on polydimethylsiloxane (PDMS), mushroom-capped, structured dry adhesives, the effective Youngʼs Modulus of the material was found to change negligibly as a result of pressure, while no changes in adhesion were observed. The effect of time spent in vacuum was also examined. Significant changes in effective Youngʼs Modulus were observed, but no changes were noted in adhesion. Tests also showed that no significant changes to adhesion could be detected from −50 to 75 °C. These results are important for space applications because it shows that the adhesion of a mushroom-capped, synthetic, PDMS, dry adhesive is constant in various thermal and pressure environments.