Plasmonics-Nanofluidics Metamaterial: An Ultrasensitive Platform for Terahertz biosensing and Quantitative Measurement of Molecules

Abstract Background: The terahertz spectroscopy has attracted enormous attention for label free chemical and biological sensing, due to the presence of molecular fingerprints and remote sensing capabilities. However, because of the strong absorption of THz waves in aqueous solutions, detecting liquid-phase biological samples by THz spectroscopy has encountered strong constraints. Results: Here, we demonstrate for the first time a rapid and label-free sensing for liquid-phase biological samples using THz spectroscopy based on microfluidic metasensors. The metasensors were integrated with microfluidic chip to precisely control the liquid sample thickness within 220 nanometer (MMS-N) and 50 micrometer (MMS-U). The metasensors include a periodic split ring resonator (SRR) with two resonant peaks in the THz range. The sensitivity(S) and corresponding figure of merit (FOM) of the two resonance peaks of MMS-N and MMS-U are analyzed with respect to different refractive index matching solution. Both the two resonance peaks of the metasensors are sensitive to the varies refractive index environment and high-frequency resonant of MMS-N shows the best sensitivity(~136GHz/RIU). In addition, the label-free biological sensing capability was conducted through qualitative and quantitative LDL and ox-LDL, where a shift of resonance frequency was observed as the LDL and ox-LDL concentration increased. Conclusions: The results indicated nanofluidic metasensor presented excellent sensing capability for liquid-phase molecular analysis by THz spectroscopy, and the proposed sensing system has the potentials to be developed as a rapid, label-free and highly sensitive detection tool for molecular analysis by THz sensing.