<p>Over the past two decades, researchers have studied metamaterials and phononic crystals to enable certain structural properties that are not found in ordinary materials. In the form of bandgaps (a frequency range in which wave propagation is forbidden), metamaterials offer an innovative and effective method to attenuate structural vibrations or noise. While the majority of metamaterial and bandgap-related studies utilize conventional hard materials such as metals and composites, this research focuses on bandgap formation in much softer stimuli-responsive hydrogels, which can achieve reprogrammable geometric and material property periodicity through periodic swelling. Hydrogels are soft materials primarily composed of crosslinked polymeric networks and water molecules. Many hydrogels have been made stimuli-responsive that can swell or shrink upon exposure to external triggers such as light radiation, relative humidity, temperature, etc. Because of their stimuli-responsiveness and biocompatibility, hydrogels have been used in many applications such as artificial organs, cell culture scaffolds, wound dressings, drug carriers, soft robots, among many others. Recently, hydrogels have also been found to exhibit less internal damping than other commonly used soft materials, which opens up new potentials for hydrogels to be used for structural dynamics and wave propagation manipulations. This research explores the reprogrammable bandgap formation in photo-responsive hydrogel-based periodic structures and studies the effects of parameters such as photo-sensitive group concentration and unit length ratio onto the width and center frequency of the bandgaps. For cantilevered hydrogel-based periodic structures that represent the simplest type of periodic systems, experimental results are validated using finite element and diatomic chain model. Both experiments and models conclude that increase in the concentration of photo-sensitive group increases bandgap width and attenuation while reducing its center frequency whereas, increase in unit cell length ratio reduces both the bandgap width and center frequency.</p>

Stimuli-Responsive Hydrogel-Based Metamaterials With Tunable Bandgaps

Paper Proceedings: https://asmedigitalcollection.asme.org/IDETC-CIE/IDETC-CIE2021/volume/85369

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