I-design terahertz microfluidic chip for attomole-level sensing

Abstract

We developed a nonlinear optical crystal-based compact terahertz (THz)-microfluidic chip with several I-design meta-atoms for attomole (amol)-level sensing of trace amounts of solution samples. The I-design meta-atom consists of a metallic strip with a micometer-sized gap sandwiched by other metallic strips. It is periodically arrayed in a row of 1 × 5 units. A point THz source locally generated by optical rectification at the irradiation spot of a femtosecond-pulse laser beam induces a tightly confined electric-field mode at the gap regions and modifies the resonance frequency when a microchannel fabricated along the space between the metallic strips is filled with solutions. Using this chip, we could detect minute changes in the concentration of trace amounts of ethanol- and glucose-water solutions and mineral water by measuring the shift in the resonance frequencies. We succeeded in detecting 472 amols of solutes in solutions less than 100 picoliters using an effective sensing area of 0.10 λ THz × 0.57 λ THz, which indicates an improvement of approximately one order of magnitude compared to the performance of existing chips. This technique compactifies THz-microfluidic chips with high sensitivity and would accelerate the development of microfluidics integrated with THz technology, such as lab-on-a-chip devices and THz micro total analysis systems.