Tunable acoustic layers enable gel-free, conformal wearable ultrasound

Abstract

Rigid probes and coupling gels still tether diagnostic ultrasound to the clinic, precluding continuous use on moving, curved, sweating human skin. We report a tunable design platform based on epoxy-polyetheramine composites enabling independently tuned matching and backing layers, spanning ranges of acoustic impedance (2.0-5.4 MRayl), attenuation (12-117 dB<middle dot>cm-1 at 2.25 MHz), and Young's modulus (4-4700 MPa). A gradient-impedance matching layer lifts fractional bandwidth from 15% to 54%, while the visco-elastic backing boosts signal-to-noise-ratio (SNR) by 9 dB without sacrificing conformity. In vivo validation through blood pressure measurements demonstrates the efficacy of these tailor-designed transducers in capturing key hemodynamic parameters, enabling continuous cardiovascular monitoring beyond traditional clinical settings. This versatile platform translates polymer network chemistry into a design process, offering a general path to gel-free wearable ultrasound and, more broadly, to on-skin acoustic, photo-acoustic, and therapeutic devices.