Impact of single and combined space environment factors on the performance of elastomer micropatterned dry adhesives

This is the authors' abstract. We don't add key points for this paper.

This study explores the effects of environmental factors in space on micropatterned dry adhesives (MDA) made from polyurethane (PUR) and polydimethylsiloxane (PDMS), inspired by the adhesion of gecko feet. These adhesives are promising for automated docking and debris capture in low Earth orbit (LEO). The research simulated a one-year exposure to thermal vacuum (TVAC), ultraviolet (UV) radiation, and atomic oxygen (ATOX) in a 500 km, sun-synchronous orbit. Subsequent adhesion tests revealed that PDMS-based samples retain moderate adhesion under UV and TVAC but degrade significantly with ATOX as a result of silicon oxide formation. PUR-based samples lose most of their adhesion after exposure to ATOX and suffer near-total adhesion loss after exposure to UV rays due to photooxidation. Interestingly, PDMS samples subjected first to UV and then to ATOX show improved adhesion, presumably due to ATOX eroding damaged material and exposing pristine PDMS. In addition to yellowing, scanning electron microscopy analysis shows further morphological changes in MDA structure such as roughening and cracking in MDA pillars that contribute to adhesion loss. Larger 400 µm-microstructures showed better resilience than the finer 50 µm-microstructures. These findings suggest that PDMS-based MDA with larger structural features may be viable for LEO missions with limited shielding, whereas PUR-based MDA would require robust UV protection. Further direct in-space tests are recommended to assess long-term MDA performance under realistic and simultaneous exposure conditions. • Four types of Microstructured Dry Adhesive samples made of polyurethane and polydimethylsiloxane, microstructured with 400 µm- and 50 µm-diameter, mushroom-shaped pillars were exposed to thermal-vacuum cycles, UV radiation, atomic oxygen, and combinations of those, simulating one year on a 500 km sun-synchronous orbit. • Subsequent adhesion tests revealed that polyurethane samples are prone to atomic oxygen and particularly to UV exposure, while polydimethylsiloxane samples loose a majority of their adhesion performance when exposed to atomic oxygen. • Polydimethylsiloxane samples with 400 µm-microstructure exposed to UV radiation regained about 90 % of their original adhesion performance when subsequently exposed to atomic oxygen. • Polydimethylsiloxane samples with 400 µm-microstructure proved most resilient to single and combined space environment factors.