Study on tunable bandgap of three-component phononic crystals based on the thermosensitive properties of hydrogels

Abstract This study proposes a novel ternary phononic crystal based on a thermosensitive polyvinyl alcohol-poly(N-isopropylacrylamide) (PVA-PNIPAm) composite hydrogel, enabling active bandgap tuning. The unit cell of this phononic crystal comprises lead scatterers, a hydrogel coating layer, and a polylactic acid substrate. The material properties of the hydrogel change with temperature, enabling continuous regulation of the low-frequency bandgap of the ternary hydrogel-based phononic crystal (THRL) through temperature variation. Numerical simulations analyzed the elastic wave propagation characteristics of the phononic crystal, while further investigations explored temperature effects on its bandgap. Experimental validation confirmed the temperature-sensitive regulation of the bandgap by the PVA-PNIPAm composite hydrogel. Furthermore, the study proposed introducing defect states through temperature field control. Results indicate that temperature-induced defects significantly influence bandgap variations. This phononic crystal structure, combining temperature-modulation capability with low-frequency anisotropy, offers a comprehensive approach for bandgap regulation. This research provides important references for phononic crystal applications in vibration control, sound insulation and noise reduction, and smart materials.