Tunable and broadband low-frequency noise control via multifunctional polyborosiloxane thin membrane gels

In this work, a multilayer structure consisted of thin membrane gels, which are formulated by the reaction of PDMS and boron, is proposed to overcome the limitations of contemporary materials employed in sound absorption applications. The membrane gels can autonomously and dynamically respond to an external stimulus, i.e., a sound pressure wave, and activate a phase transition in their polymeric network, with energy absorbed in this phase transition and resulting in high acoustic performance. It was demonstrated that the membrane gels were able to achieve high and dynamic sound absorption individually (≥90%), which dynamically shifted to lower frequencies when the sound amplitudes were increased. The combination of multiple membranes resulted in the occurrence of multiple absorption coefficient peaks (60-85%) over a wider range of frequencies with the same dynamic shift. These results demonstrated that the proposed prototype of thin membrane gels can be used to develop deep subwavelength absorbers with highly tunable acoustic properties, displaying their potential application value in various sound absorption applications.