High-Definition Diagnostic Ultrasound Technology Constructed on Nanoscale Level

The groundbreaking transducers, which are orders of magnitude smaller than current systems, are so tiny that up to 500 of the smallest could be positioned across the width of one human hair.

While at an early stage these devices offer a multitude of possibilities for imaging and measuring at scales a thousand times smaller than traditional ultrasound technology. They can be made so small they could be placed inside cells to perform intracellular ultrasonics. They can produce ultrasound of such a high frequency that its wavelength is smaller than that of visible light. Hypothetically, they make it possible for ultrasonic images to take finer pictures than the most powerful optical microscopes.

The research, conducted by the Applied Optics Group in the division of electrical systems and optics at the University of Nottingham (UK), has been considered so potentially innovative that in 2009 it was awarded a GBP 850,000 five-year Platform Grant by the Engineering and Physical Sciences Research Council (EPSRC; Swindon, UK) to develop advanced ultrasonic techniques. The team has also been supported by additional funding of GBP 350,000 from an EPSRC grant to strengthen aerospace research.

Dr. Matt Clark, of the Applied Optics Group, said, "With the rise of nanotechnology you need more powerful diagnostic tools, especially ones that can operate nondestructively and ones which can be used to access the mechanical and chemical properties of the samples at this scale. These new transducers are hugely exciting and bring the power of ultrasonics to the nanoscale.”

The ultrasonic transducers are made up of sandwich or shell-like structures painstakingly engineered to possess both optical and ultrasonic resonances. When hit by a pulse of laser, light they are set ringing at high frequency, which launches ultrasonic waves into the sample. When excited by ultrasound, the transducers are very slightly deformed and this changes their optical resonance, which are detected by a laser.

The devices can be constructed either by micro/nano lithography techniques similar to those used for microchips or by molecular self-assembly in which the transducers are constructed chemically. Possibly the most recognizable application of ultrasonics is medical imaging but it is also widely used in engineering applications and for chemical sensing. These tiny transducers open up the possibility of using these techniques on the smallest scales, for instance, inside cells and on nano-engineered components.

Dr. Clark noted, "Imagine imaging inside cells in the same way that ultrasonic imaging is performed inside bodies. Theoretically, we could get higher resolution with the nano-ultrasonics than you can with optical microscopes and the contrast would be very interesting. In addition, the transducers can be made into highly sensitive chemical sensors ultrasonics SAW sensors are used on the normal scale for electronic noses this would allow you to distribute chemical sensors in tissue or in paint so you could make paint with chemical sensors to detect corrosion or explosives in it.”

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