Adhesion and Wetting Properties at Functionalized Soft Interfaces

Abstract

Soft matter systems exhibit remarkable capabilities for mechanical, chemical, and morphological transformations in response to external stimuli, enabling diverse functional applications. This thesis advances the design and fundamental understanding of functional soft materials through three interconnected investigations: surface instabilities, magneto-responsive interfaces, and dynamic mechanical behavior.

In the first study, we investigate how swelling-induced instabilities in ultra-soft polydimethylsiloxane (PDMS) gels generate permanent crease instabilities that enhance adhesion across multiple length scales. These creasing patterns increase interfacial energy by modulating contact line geometries, offering a scalable and biologically relevant strategy for tuning surface adhesion.

The second investigation focuses on fabricating an advanced magneto-active elastomeric surface with pre-encoded microstructures. By integrating soft elastomeric substrates with magnetic field-guided pre-structuring, we achieve superhydrophobic surfaces exhibiting stimuli-responsive wetting, self-cleaning, and dynamic fluid manipulation. The synergy between surface softness, tailored roughness, and magnetic actuation unlocks novel regimes of droplet impact and control, with potential applications in microfluidics and soft robotics.

The final segment presents preliminary findings on the large-amplitude shear response of magnetoactive elastomers (MAEs) under cyclic deformation, highlighting the in-fluence of particle volume fraction and pre-encoded structures within the matrix. Experimental findings reveal that both magnetic activation and pre-structural alignment significantly amplify energy dissipation through magneto-mechanical coupling. The enhanced hysteresis in anisotropic MAEs demonstrates a promising route to engineer soft materials with tunable mechanical damping for advanced functional applications.

Collectively, this thesis highlights the critical interplay between structure, softness, and external stimuli in the design of adaptive soft interfaces and materials. The insights gained establish a foundation for future innovations in smart materials, adhesive technologies, and energy-dissipative systems.

Date of Award	2025
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Qin XU (Supervisor)