Invited Article: Terahertz microfluidic chips sensitivity-enhanced with a few arrays of meta-atoms

Hironaru Murakami,Masayoshi Tonouchi,Kazunori Serita,Iwao Kawayama,Kosuke Okada,Eiki Matsuda

doi:10.1063/1.5007681

Abstract

We present a nonlinear optical crystal (NLOC)-based terahertz (THz) microfluidic chip with a few arrays of split ring resonators (SRRs) for ultra-trace and quantitative measurements of liquid solutions. The proposed chip operates on the basis of near-field coupling between the SRRs and a local emission of point like THz source that is generated in the process of optical rectification in NLOCs on a sub-wavelength scale. The liquid solutions flowing inside the microchannel modify the resonance frequency and peak attenuation in the THz transmission spectra. In contrast to conventional bio-sensing with far/near-field THz waves, our technique can be expected to compactify the chip design as well as realize high sensitive near-field measurement of liquid solutions without any high-power optical/THz source, near-field probes, and prisms. Using this chip, we have succeeded in observing the 31.8 fmol of ion concentration in actual amount of 318 pl water solutions from the shift of the resonance frequency. The technique opens the door to microanalysis of biological samples with THz waves and accelerates development of THz lab-on-chip devices.

Highlights

Microfluidic devices such as micro-total analysis systems have attracted significant attention as promising tools for medical diagnosis and biological analysis.[1,2,3,4,5] These devices generally consist of integrated chemical equipment connected with microfluidic channels with dimensions of tens to hundreds of micrometers
One of the advantageous properties of these devices is that only picoliter volumes of liquid solution is required because the volume of the microfluidic channel is much smaller than that required by conventional chemical instruments
There are several research studies addressing the issue of development of high-sensitive THz sensors for ultra-trace measurements of liquid solution by using, e.g., resonators,[18,19] dielectric waveguide systems,[20] and meta-surfaces,[21] and majority of which focused on the use of the farfield THz waves

Summary

Introduction

Microfluidic devices such as micro-total analysis systems have attracted significant attention as promising tools for medical diagnosis and biological analysis.[1,2,3,4,5] These devices generally consist of integrated chemical equipment connected with microfluidic channels with dimensions of tens to hundreds of micrometers. There are several research studies addressing the issue of development of high-sensitive THz sensors for ultra-trace measurements of liquid solution by using, e.g., resonators,[18,19] dielectric waveguide systems,[20] and meta-surfaces,[21] and majority of which focused on the use of the farfield THz waves.

Results

Conclusion