Arbitrarily Shapeable Couplant with Fluidity Onset for Conformal Ultrasound

Couplant is indispensable for ultrasound examinations. However, shape adaptability and operational feasibility, which are both crucial, cannot be provided conjointly by existing couplants due to their either liquid or solid form. Here an ideal couplant composed of fibers and dynamically cross-linked polysilicone is reported, which exhibits a unique solid-to-fluid transition upon application of stress exceeding a threshold. Together with the acoustically transparent feature, the particularity of the stress-triggered fluidity allows conformal adapting to arbitrary geometries under stress exertion and stable preserving for long-term and reliable ultrasound examination after stress release. Steeply curved geometries and pressure-sensitive tissues, which are extremely challenging for the state-of-the-art ultrasound modalities, are successfully graphed or treated. This couplant integrates the merits of liquids and solids, providing new opportunities for various ultrasound in industrial and medical fields.