The sensor is based on a split-rib optomechanical waveguide fabricated using novel CMOS-compatible processing that is sensitive to ultrasound vibrations. As a result the sensor can be small at 20-micron dimensions and has a detection limit two orders of magnitude better than piezoelectric elements of identical size.
The low detection limit of the sensor enables new clinical and biomedical applications of ultrasonic and photoacoustic imaging such as deep-tissue mammography and the study of vascularization or innervation of potential tumorous tissue. One of the problems with piezoelectric sensors is that to achieve high sensitivity the sensor must be physically large which works against distance resolution. An array of small sensors achieves resolution but with an inherently noisy image. Second, piezoelectric sensors rely on their mechanical resonance to enhance signal amplitude and this means they only operate in a small range around the resonance frequency.
"The sensor we have demonstrated will be a game-changer for deep tissue imaging in otherwise non-transparent tissues such as skin or brain. For applications such as sub-cutaneous melanoma imaging or mammography, it enables a more detailed view of the tumor and vascularization around, aiding in a more detailed diagnosis," said Xavier Rottenberg, fellow wave-based sensors and actuators at IMEC, in a prepared statement.
A matrix of sensors on a 30-micron pitch can be integrated on a chip with photonic multiplexers allowing simpler connection and ease of use in catheters.
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