Wearable devices that continuously monitor human physiology in a noninvasive manner are gaining prominence in precision and digital medicine. While existing wearables successfully record surface-level signals, clinical-grade imaging of internal organs remains a challenge.
Ultrasound imaging, with its zero radiation and ability to evaluate organ functions, holds promise for continuous monitoring. However, conventional wearable ultrasound devices face issues of wearability and limited applicability to various body parts.Â
A breakthrough is presented in the form of a Bioadhesive Ultrasound (BAUS) device. This thin and rigid ultrasound probe is ingeniously adhered to the skin via a soft, tough, antidehydrating, and bioadhesive hydrogel-elastomer hybrid couplant. Unlike previous wearables, this device offers high-density elements (400 per square centimeter), stable positions during body motions, and extended reliability over 48 hours.Â
The BAUS probe comprises an array of high-performance piezoelectric elements with varying frequencies (3, 7, or 10 MHz). Fabrication methods include 3D printing, laser etching, and photolithography for circuitry. The top and bottom circuits are covered by acoustic backing and matching layers, optimizing acoustic transmission. The BAUS couplant, encapsulated in a thin elastomer membrane, consists of a bioadhesive layer for secure skin attachment, maintaining robust adhesion under various conditions.Â
A mechanical model demonstrates the robust adhesion of BAUS on the skin, outperforming conventional couplants. Interfacial toughness measurements over 48 hours reveal consistent and strong adhesion in both dry and wet conditions. The BAUS couplant exhibits low acoustic attenuation coefficients, ensuring effective transmission of acoustic waves. Moreover, the device withstands high pulling forces, maintaining stability during the 48-hour period.Â
BAUS probes showcase superior axial and lateral resolutions compared to existing wearables. The BAUS system’s capability for continuous imaging of various organs is demonstrated, including blood vessels, muscles, lungs, diaphragm, heart, and stomach. Subjects report minimal discomfort during 48-hour wear, emphasizing the device’s biocompatibility.Â
The BAUS system’s continuous imaging potential opens avenues for clinical applications in monitoring patients in intensive-care units. While the current data acquisition system is external, future miniaturization aligns with the trend of point-of-care ultrasound devices. Beyond clinical settings, the BAUS platform holds promise for long-term imaging of tissue and organ development, embryonic monitoring, and noninvasive tracking of tumors and brain activity.Â
The Bioadhesive Ultrasound (BAUS) device represents a paradigm shift in biointegration, offering a novel approach to continuous, noninvasive imaging of internal organs. The successful 48-hour monitoring of various physiological aspects demonstrates its potential for clinical applications and broader implications in the field of wearable medical devices. Future refinements in probe design and miniaturization of data acquisition systems could further enhance its usability and pave the way for diverse applications in precision medicine.Â
In summary, the BAUS device’s innovative coupling of a high-performance ultrasound probe with a bioadhesive couplant heralds a new era in wearable medical technology, promising continuous and reliable monitoring of internal organs for improved healthcare outcomes.Â
Journal Reference ,Â
Bioadhesive ultrasound for long-term continuous imaging of diverse organs.Science377,517-523(2022).DOI:10.1126/science.abo2542. Â
