A user-friendly, tunable biosensor customized for the terahertz range has been developed by scientists at the Tokyo Institute of Technology.
(a) A photograph of the spiral bull’s eye (SBE) structure, (b) a microscope image of the double-corrugated devices, and (c) a scanning electron microscope image of the eight-tip Siemens-star aperture at the center of the SBE structure. (Image credit: Scientific Reports)
Images of mouse organs taken with the help of the new device show that the sensor has the potential to differentiate between various types of tissues. The feat widens the prospects for terahertz applications in future diagnostics and biological analysis.
The term plasmonics refers to the study and applications of phenomena associated with the interaction between metal surface electrons and light. Materials based on plasmonics are of interest in developing technologies as wide as high-performance electronics to ultra-sensitive biosensors.
Researchers are investigating the prospects of blending the benefits of plasmonics with emerging terahertz technologies as a means to devise innovative and improved techniques for non-invasive detection and analysis. However, until now, the potential to detect extremely small biological samples has been difficult, specifically because of the fact that the wavelengths of terahertz light waves are longer than those of infrared, visible, and ultraviolet light.
At present, Yukio Kawano and his team from Tokyo Tech’s Laboratory for Future Interdisciplinary Research of Science and Technology worked together with scientists at Tokyo Medical and Dental University to find a means to solve this problem by designing a frequency-tunable plasmonic-based terahertz device.
One of the main aspects of the new device is its spiral bull’s eye (SBE) design. Owing to its smoothly varied grooves, “the groove period continuously changes with the diameter direction, resulting in continuously frequency-tunable characteristics,” states Kawano in the study published in
Another benefit of the innovative design is that it includes what is known as a Siemens-star aperture, which allows an easy-to-use means for selecting the desired frequency by just varying the rotation of the spiral plasmonic structure.
The device also increases the electric field intensity at the subwavelength aperture, thus significantly amplifying the transmission.
Yukio Kawano, Tokyo Institute of Technology
As part of the initial experiments to evaluate how well the new device could image biological tissues, the scientists acquired terahertz transmission spectra for different mouse organs. For performing further exploration, they also performed terahertz mapping of mouse tails. The study, which involved comparing images acquired with and without the SBE design, revealed that the former resulted in an evidently enhanced potential to distinguish between different tissues like skin, hair, and bone. The study outcomes indicate that the enhanced performance is the result of the tunability of the device.
Technical support for the study was provided by Tokyo Tech’s Semiconductor and MEMS Processing Center.
The researchers intend to perform further exploration to test the new device with different mouse organ tissues. The outcomes pave a new path for plasmonic-based terahertz imaging of biological samples, which could ultimately result in the development of enhanced, non-invasive diagnostic imaging tools.