Reversible tunable topological phononic crystals based upon thermo-acoustic hydrogels

Area of Science:

• Acoustics
• Materials Science
• Condensed Matter Physics

Background:

• Topological phononic crystals (TPCs) offer unique one-way acoustic wave propagation, immune to scattering.
• Traditional TPCs lack reconfigurability, limiting their application to fixed frequencies.
• Achieving tunable bandgaps and topological edge states (TES) in TPCs remains a significant challenge.

Purpose of the Study:

• To develop a reconfigurable topological phononic crystal (TPC) with tunable acoustic wave transmission.
• To investigate the use of thermosensitive hydrogels for dynamic control of TES.
• To demonstrate continuous frequency tuning of the phononic bandgap and TES without altering structural geometry.

Main Methods:

• Integration of thermosensitive poly-N-isopropylacrylamide (PVA-PNI-PAm) hydrogel into TPC structures.
• Exploration of hydrogel's hydrophilic-hydrophobic transition to control acoustic wave propagation.
• Experimental realization of reversible state transitions in the hydrogel and their effect on TES.

Main Results:

• Demonstrated reversible on/off switching of TES within the TPC by altering hydrogel state.
• Showcased continuous tuning of the central frequency of the phononic bandgap and TES.
• Confirmed that TES tuning is achieved by varying sound group velocity, not structural geometry.

Conclusions:

• The proposed TPC with PVA-PNI-PAm hydrogel offers a reconfigurable platform for acoustic wave manipulation.
• This technology enables dynamically programmable functionalities for intelligent acoustic devices.
• Potential applications include acoustic wave guiding, integrated acoustics, and acoustic information processing.