Researchers from the Institute of Laser Engineering at Osaka University established a prototype terahertz optical spectroscopy system with a sensing area identical to the cross-sectional region of just five human hairs. By assessing the shift in peak transmittance wavelength of a terahertz radiation source, the concentration of actual trace dissolved contaminants in a tiny droplet of water can be measured. This work may steer to portable sensors for aspects such as the early detection of diseases, drug development, and water pollution monitoring.
Presently, a team of researchers at Osaka University has utilized a proprietary terahertz radiation source in a microfluidic chip encompassing a metamaterial structure to quantify the amount of trace contamination in water. “Using this lab-on-a-chip system, we could detect minute changes in the concentration of trace amounts of ethanol, glucose, or minerals in water by measuring the shift in the resonance frequencies,” first author Kazunori Serita says.
The I-design includes a metallic strip with a micrometer-sized gap sandwiched by other metallic strips. It is occasionally arrayed in a row of five units, which form a kind of “meta-atom,” in which peak optical transmittance varies based on the existence of trace contamination by dissolved molecules. This device applies the point terahertz source technology formerly developed at Osaka University. A minor terahertz light source was developed by the irradiation spot of a femtosecond-pulse laser beam that generates a tightly confined electric-field mode at the gap regions. It then amends the resonance frequency when a microchannel fabricated in the space between the metallic strips is recharged with the sample solution.
“We succeeded in detecting just 472 attomoles of solutes in solutions with volumes of less than 100 picoliters, which is an order of magnitude better than existing microfluidic chips,” senior author Masayoshi Tonouchi announces. This work can direct to substantial improvements in mobile sensing, both in terms of sensitivity and the quantity of liquid required.
