Wear mode control of polydimethylsiloxane (PDMS) by load and composition

Soft robots moving over dry or wet surfaces increasingly rely on common laboratory elastomers like polydimethyl siloxane (PDMS) for reliable locomotion due to compliance matching to soft actuators and the relatively high surface energy. In this study we quantify the wear of PDMS of three compositions (5:1, 10:1, and 20:1 base-to-binder ratio) under moderate loading in order to provide design guidelines for durable and wear-resistant PDMS surfaces. Each sample underwent 100 m of sliding by an instrumented steel probe, and the wear scars were assessed by optical profilometry. For the 10:1 composition, the wear had standout features indicating microploughing abrasion at low loads, but microcutting abrasion at higher loads, with an interim-load transition period of suppressed wear. Wear of the softer 20:1 composition was more uniform for the tested loads, and its compliance suggests a combination of fatigue-based wear and abrasive wear. We conclude that the moderate properties of the 10:1 composition allow the PDMS to remain relatively wear-resistant, especially under applied pressures at approximately ~10% of its Young's modulus.