A Modular, Bubble-Infused, Hydrogel Ultrasound Wearable for Minimally Invasive Biochemical Monitoring.

While miniaturized wearable ultrasound technologies excel at physiological monitoring, detecting small-molecule biochemicals remains challenging due to their inherent "acoustic invisibility". To address this, we establish a mechano-acoustic transduction mechanism that translates biochemical stimuli into quantifiable acoustic signatures. Central to this approach is a "Core-Shell Cell" (CSC) architecture, comprising a bubble-infused hydrogel core encapsulated by a stimuli-responsive hydrogel shell. Upon exposure to target analytes, the responsive shell swells and exerts compressive stress on the core, inducing measurable shifts in the transmitted ultrasound spectrum. Implementing this strategy, we develop a modular, wrist-worn ultrasound device featuring a minimally invasive microneedle interface. Using in vitro and ex vivo models, we demonstrate the expandability of the device through continuous monitoring of pH and glucose, capturing critical pathological variations for diabetic ketoacidosis and hyperglycemia alerts. Validated by systematic characterizations, this work endows wearable ultrasound with "biochemical vision", establishing an adaptable strategy for multi-analyte profiling.