How swelling affects microscale creasing and stick-slip friction of soft elastomers

We investigate how swelling alters microscale stick-slip instabilities between a glass microparticle and swollen soft elastomer, observed through lateral force microscopy and simultaneous confocal microscopy. Our findings indicate that stick-slip behavior persists, even in moderately swollen states. Incremental increases in swelling lead to incremental decreases in stick-slip and the friction force. Above a critical degree of swelling, stick-slip is suppressed, and smooth sliding emerges. We attribute this to the fact that while the silicone network deforms, the swelling liquid can also separate from network to afford a lubricating effect. We also observe that steady stick-slip motion is achieved after initial creases slip across the contact zone, where swelling accelerates how long it takes to reach the steady kinetic friction regime. • Microscale friction behavior of soft and swollen elastomers is studied by a combination of lateral force colloidal probe microscopy and laser scanning confocal microscopy • Upon incremental swelling, there is a transition of stick-slip friction on a sticky elastomer to smooth sliding. • Incremental increases in swelling lead to incremental decreases in stick-slip amplitudes and friction force, suggesting that contact is a combination of liquid and network molecules until a full lubricating layer completely suppresses creasing instabilities. • Increases in swelling leads to a quicker transition from static friction to the steady-state kinetic friction regime.