Light and Sound

Time variant light can be used to generate sound from any material. The field is known as photoacoustics and forms one of the primitive fields with its roots of discovery in the hands of Alexander Graham Bell in the year of 1880. Several developments in the field took place which lead to the creation of one of the most sophisticated Biophotonics functional imaging platform, capable of probing living tissues in the deep.

I have been working in this field since 2019 and have explored several directions:

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Optofluidics with pulsed photoacoustics - In this project, I have created micro and meso scale fluid channels using cleanroom techniques such as SU8 lithography and Deep Reactive Ion Etch, and have used these channels to sense the concentration of various pigments dissolved in a base solvent. One of such examples is finding the concentration of the methylene blue dye. Photoacoustic maps of the channels filled with dye was also obtained as a demonstration of the working of the photoacoustic experimental setup. The transduction principle works well with a sensitivity of ~80 mV/mM. This technique forms one of the basic verifications of the usage of photoacoustic on microfluidic channels, and can be used to functionally image and understand various complex biological mechanisms such as the diffusion of oxygen into blood, etc.

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Photoacoustics with flexible linear array ultrasound transducer - In this project, I have fabricated flexible ultrasound transducer and have applied it for combined ultrasound and photoacoustic imaging application. For that, it was necessary to establish backend connections by designing a custom pcb and thus connecting the transducer to the Vantage 256 Research Ultrasound System from Verasonics Inc. The big picture is to come up with stretchable ultrasound transducer which would conform to the skin of the mother and thereby functionally image the health conditions of the fetus a couple of months prior to birth, thereby predicting any kind of birth complications.

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Photoacoustics with Piezoelectric Micromachined Ultrasound Transducers (PMUTs) - PMUTs having AlN thin film piezoelectric layer were fabricated in a certain fashion to be used for non-invasive functional imaging of a neonate's brain right after the birth. An experimental arrangement in the form of a small helmet was made into which the transducers were fitted following a modulated fashion which was subsequently fitted with optical fibers for effective illumination.