Nanofiber‐Based Photoacoustic Sensors for In Vivo Diagnostic Imaging

ABSTRACT Achieving both broad bandwidth and high frequency in a single sensor is challenging but essential for high‐resolution heterostructure photoacoustic diagnostic imaging. Such capabilities can provide early‐stage disease detection signatures and eliminate need for multiple sensors. While promising, we present the first fabrication and demonstration of nanofiber‐based photoacoustic sensors, enabling high‐frequency broad‐bandwidth photoacoustic (PA) signal detection due to the flexible nanofibers' network that allows the absorption of acoustic energy over large frequency range and conversion of mechanical vibrations into electrical signals efficiently. A customized electrospinning system is designed for synthesizing nanofibers on a heated substrate using composite solution of polymer PVDF‐TrFE and cubic single‐crystal nanoparticles. Synthesized nanofibers provide a large surface area, with BTO around the surface of nanofibers, resulting in higher polarization, crystallinity, and charge generation while making proper electrical contact using loaded high pressure. These composite nanofibers are characterized and optimized for sensor fabrication. Fabricated sensors are used to detect photoacoustic signals from various sources including eumelanin and hemoglobin. Photoacoustic signals of central frequencies (1.5–33.2 MHz) and bandwidth (209%) are recorded. The sensors are further used for PA imaging with a human subject and a chicken phantom, showing potential applications of the developed sensors in clinical diagnostics.