A photoacoustic patch for three-dimensional imaging of hemoglobin and core temperature

Abstract

Electronic patches, based on various mechanisms, allow continuous and noninvasive monitoring of biomolecules on the skin surface. However, to date, such devices have been unable to sense biomolecules in deep tissues, which have a stronger and faster correlation with the human physiological status. Here, we demonstrate a photoacoustic patch for three-dimensional (3D) mapping of hemoglobin in deep tissues. This photoacoustic patch integrates an array of ultrasonic transducers and vertical-cavity surface-emitting laser (VCSEL) diodes on a common soft substrate. The high-power VCSEL diodes can generate laser pulses that penetrate >2 cm into human tissues and activate hemoglobin molecules to generate acoustic waves, which can be collected by the transducers for 3D imaging of the hemoglobin with a sub-millimeter spatial resolution. Additionally, the photoacoustic signal amplitude and temperature have a linear relationship, which allows 3D mapping of core temperatures with high accuracy and fast response. The results of 3D core temperature mapping and long-term monitoring in ex-vivo and in-vivo studies are validated by commercial devices. With access to biomolecules in deep tissues, this technology adds unprecedented functions to wearable electronics and thus holds significant implications for various applications in both basic research and clinical practice.