“Wetting and adhesion of soft, wet, or swollen surfaces”
Soft materials are found in a host of applications, from biotechnology and 3D printing to adhesives and soft devices. However, understanding the behavior of soft interfaces is an ongoing challenge. When materials are sufficiently soft, or the characteristic size scale is sufficiently small, soft crosslinked solids can display liquid-like characteristics – properties traditionally reserved for liquids emerge as an important part of the material response. Moreover, when the materials are swollen polymer networks, the swelling fluid can also provide true liquid behavior. In this talk, we present situations where combinations of solid and liquid characteristics control behavior of soft deformable surfaces. In particular, we illustrate the importance of surface tensions and fluid separation for the wetting of a liquid drop on soft and swollen polymer networks. Based on confocal microscopy images, we propose a theory for fluid separation and network deformation near the contact line. In the second part of the talk, we discuss how solid surface tension can play a role in the microscale contact mechanics of an oil-coated soft substrate. Time permitting, we will introduce our current knowledge microscale friction of soft and adhesive interfaces.