Mechanics of Miniature Surface Craters for Reversible Adhesion

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This award supports fundamental research on the mechanics of cratered surfaces. Reversible adhesives are designed to form temporary bonds, and ideally can be reusable and capable of strong bonding. Such reversible adhesives can find wide applications in vertical mounting and climbing, releasable wafer and chip handling, as well as reusable bio-integrated electronics. It is well known that reversible adhesion can be achieved through surface interactions such as van der Waals (vdW), capillary, and electrostatic forces as well as volume effects such as suction. Adhesion due to surface interactions has been well studied for gecko-inspired microfibrils with different tip shapes including the concave shape. But the contribution from suction has been widely neglected at microscale. However, manufacturing microfibrils with large aspect ratio can be expensive and time-consuming. If an array of meso-scale craters could provide combined high adhesive strength and reversibility, they may become a practical substitute for microfibrils. The results of this research will guide the design and optimization of cratered surfaces and give a definitive answer to the debate of the suction effect across a broad range of scales. It will also create a pathway for developing a new class of superior adhesives for various applications in engineering and medicine. Building upon the strong track record of previous educational and outreach activities, the PIs will continue to provide research opportunities specifically designed for undergraduate and high-school students from minority institutes through NASCENT REU and women in engineering programs (WEP) at UT Austin.The research objective of this research is to test the hypothesis that arrays of miniature craters on polymer surfaces can lead to significantly improved reversible adhesion with pressure-sensitive strengths. The premise of this research is that cratered surfaces can be tailored for various applications, by choosing proper geometric and mechanical properties, as well as the preloading program. Central to this tailoring is a fundamental multi-scale understanding of the adhesion and decohesion mechanisms. The research team plans to develop a fundamental understanding of reversible adhesion of cratered polymeric surfaces in a broad range of scales through the following three research thrusts: (i) Fabrication of surface craters with sizes ranging from centimeters to micrometers. (ii) Measurements of traction-separation relations and pull-off forces. (iii) Modeling and simulation. The project will be carried out by a synergetic team with complementary expertise in microfabrication, adhesion mechanics, modeling, and simulation.