Pressure sensitive adhesives are a class of materials that bind to a substrate after a light external pressure has been applied. They are used extensively in daily life for adhesion to dry and rigid surfaces. These materials have not been extended to other important application areas ranging from healthcare to construction where the surfaces are soft, wet, and slippery, such as skin, tissue, or wounds. These materials are often soft and can deform under pressure. The mechanical properties of these soft materials, not just their surface, can affect the ability to adhere to that surface. This research will determine the fundamental relationships between the properties of a substrate and the performance and failure of adhesives. A better understanding of performance and failure mechanisms for adhesives on soft and wet surfaces could have important impact in industries as diverse as health or flexible wearable electronics where new innovative adhesives could open new technological applications. This work will also engage high school and undergraduates in an intensive exposure to research and materials.
The viscoelastic nature of pressure sensitive adhesives makes understanding their mechanical response challenging, especially in the limit of large strains. The project aims to provide the needed knowledge for the performance of pressure sensitive adhesives on compliant and wet surfaces by testing two scientific hypotheses. First, increasing the substrate compliance should increase the size of the dissipation zone at a crack tip, and affect the performance & mode of failure of adhesives. Second, the importance of surface energy over bulk dissipation should increase for adhesion on wet surfaces. To test these hypothesis a better fundamental understanding of stress concentration within an adhesive in stratified systems as well as of the change in their surface energy upon exposure to water will be acquired. This research systematic experimental approach is divided into three aims. (1) Develop an advanced toolkit to study the performance of pressure sensitive adhesives on soft, wet, and slippery surfaces, (2) Understand peeling adhesion of pressure sensitive adhesives from soft and wet surfaces, and (3) Characterize tack on soft and wet substrates. The outreach and educational components include a partnership with local high schools to engage students in the research experience with a focus on underrepresented students.
