Development of photoacoustic microscopy for the detection of microplastics in fisheries and aquaculture

Photoacoustic microscopy is a hybrid technique of optical and acoustic microscopy where acoustic waves are generated optically and detected using acoustic transducer. It has recently attracted strong attention in the domain of in vivo imaging due to its unique advantage of achieving high resolution at deep imaging depth, which is difficult to be achieved with the individual technique. In the present work, we have performed photoacoustic imaging of two different types of standard samples/material and systematically characterized the behavior of the emitted acoustic signal’s bandwidth. First, acoustic transducers of different central frequencies varied from 10 MHz to 50 MHz are utilized to investigate the highest emitted acoustic signal frequency and amplitude from both the materials. Secondly, energy and power of the optical waves are varied keeping fixed acoustic transducer which produced the highest amplitude of the acoustic signal to understand the sensitivity limit of photoacoustic microscopy. Further, a detailed investigation is conducted to sense the ultrasonic waves using multiple frequency transducers both in plane parallel and focused mode. Similar optimization of the system is conducted for the fisheries and aquaculture biological samples. The optical and acoustic resolution of photo-acoustic microscopy is also demonstrated in fish tissue for detection of the microplastics migrated through the fish scales. The study is envisioned to detect and image the micro-particle pollution in marine fishes.