Design and Fabrication of Water-Repellent Flexible Adhesive Patches Using Bioinspired Structures and Materials

Abstract

Functional adhesives play a pivotal role across diverse fields, such as biomedical devices, flexible electronics, wearable technologies, and soft robotics. However, conventional adhesives often face critical limitations in wet environments due to interfacial water layers, which impede conformal contact, weaken adhesion, and ultimately compromise the reliability of their functional performance. While bioinspired adhesive systems that integrate water-repellent microstructures have been developed to address these challenges, the inherent trade-off between water repellency and adhesion strength continues to limit their effectiveness, as such structures often prioritize water expulsion at the cost of reduced adhesive performance. In this dissertation, we propose innovative hybrid bioinspired strategies to enhance adhesion performance in wet environments. By integrating microstructured water-repellent surfaces with bioinspired protruding tip architectures and shape memory polymer (SMP) materials, we achieve a breakthrough in overcoming the trade-offs between water repellency and adhesion strength. These approaches combine the unique advantages of hierarchical microstructures and stimuli-responsive materials, enabling robust, scalable, and versatile adhesion solutions. In Chapter 2, we present a bioinspired water-repellent adhesive with self-attachability based on mushroom-shaped microstructures, which include protruding tip architectures. These structures enhance water repellency while simultaneously increasing adhesion strength by uniformly distributing stress and maximizing the contact area. The resulting adhesive demonstrates exceptional adaptability to rough and wet surfaces, maintaining high adhesion performance. In Chapter 3, we introduce a strong and reversible water-repellent adhesive by integrating thermoresponsive SMP materials into hydrophobic micropillars. The hydrophobic micropillar arrays reduced the solid-liquid contact area, effectively expelling water to form stable dry contacts. Simultaneously, the SMP matrix dynamically modulated its stiffness, allowing conformal contact in the rubbery state and enhanced adhesion in the glassy state. This dual functionality enabled the adhesive to achieve a high wet adhesion strength, while maintaining strong adhesion across different substrate sizes and roughness levels. Additionally, the adhesive exhibited excellent shape recovery properties, allowing for tunable adhesion states and reusability. The findings presented in this dissertation establish a foundation for next-generation adhesive technologies that seamlessly integrate bioinspired structures and materials to address the critical challenges of adhesion in wet environments. By overcoming the limitations of conventional adhesives in wet conditions, these systems enable robust, reversible, and residue-free adhesion. This transformative approach holds significant promise for applications requiring reliable performance under wet or submerged conditions, including wearable electronics, biomedical devices, and soft robotics.