Nanotechnology has enabled scientists to develop tiny devices for various fields of research such as engineering and medicine. German researchers have recently developed the smallest ultrasound detector at almost 0.1 inches by 0.2 inches.

A team from the Technical University of Munich have recently published their research in the journal Nature, titled "Ultrasound detectors use high-frequency sound waves to image objects and measure distances". However, the resolution of the readings is often limited by the physical dimensions of the detector.

A traditional ultrasound detector, such as the machine used for medical tests uses soundwaves to capture live images of internal body parts or sonography. However, a sonograph can sometimes miss small details. For example, an ultrasound for pregnant women is recommended at the six weeks of pregnancy for the baby to be detected and seen in the images.

Creating a Miniature Ultrasound Detector

Challenges the scientists faced included size reduction of certain parts of ultrasound detectors such as optical microring resonators or piezoelectric transducers that would only have a limited bandwidth range. The create the miniature detector, they used silicon-on-insulator technology.

The sensing area of the ultrasound detector is only 200 by 500 nanometers placed on top of a silicon chip. The tiny area is then sensitive to even the smallest signatures and can create super-resolution imaging.

Instead of using piezoelectric crystals, which release electrical charges that control light intensity, the scientists used mini photonic circuits instead. The new device is called a silicon waveguide-etalon detector (SWED).

Rami Shnaiderman said that their device is smaller than the size of a blood cell. This is the first time such a device was designed to be this minuscule. "If a piezoelectric detector was miniaturized to the scale of SWED, it would be 100 million times less sensitive," he added, explaining why the crystals had to be replaced by photonic circuits.

Using silicon photonics enabled the team to retain the high-sensitivity of the ultrasound detector, shared Professor Vasilis Ntziachristos. The SWED is about half a micron in size or nearly 10,000 times smaller than piezoelectric detectors used in the medical field. The device is also detected ultrasound wavelengths 200 times smaller than other detectors to create super-resolution imaging.

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Multiple Applications of the Device

The silicon platform also makes the device easy to manufacture where a lot of mini ultrasound detectors can be produced and is inexpensive compared to piezoelectric detectors. Schnaiderman shared that the team will continue to optimize their device so that it could be "implementation in hand-held devices and endoscopes." An endoscope is a flexible tube with a small camera and light used to take images of the digestive tract in an endoscopy.

Originally designed for optoacoustic imaging for research at the university, shared Ntziachristos, the team eventually foresaw "applications in a broader field of sensing and imaging," especially for biomedical research and clinical diagnostics on a cellular level. They hope the technology can be expanded for industrial applications as well.

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