Terahertz Microfluidic Biosensing Platform Based on Intense Wave-matter-interaction Channels

Abstract

Non-invasive and label-free detection and characterization of hazardous chemical and biological molecules is deemed as one of the holy grails of terahertz potentials. To-date, breakthrough research in metamaterial sensing has overcome quite a few bottlenecks such as light harvesting, wave-matter interaction, and sensitive signal retrieval. Longstanding issues towards a lab-on-chip approach like aqueous absorption, interaction efficiency, readout signal and integration still demand the THz community to grapple with. Inspired by the electromagnetically induced transparency (EIT) sensing structure, here proposes an ultrasensitive terahertz sensing platform targeting at microfluidic biological analyte. In the paired ring resonator (PRR) design, a flexible and low-permittivity polyimide (PI) film with marginal metallization serves as a cap of the microfluidic channel, which significantly enhances the sensing response with ultrahigh normalized sensitivities of 0.47/RIU (refractive index unit, RIU) and 0.51/RIU at 0.76 THz and 1.28 THz, respectively. In the hybrid asymmetrical split ring resonator (ASRR) design, the maximized light-matter interaction overlap has been attained by means of identical dielectric meta-atoms right under the metallic unit cells, begetting higher dual-band normalized sensitivities of 0.53/RIU and 0.59/RIU at 0.92 THz and 0.69 THz, respectively. The trapped mode resonators confine electromagnetic fields in extremely subwavelength space and hence allow for enhanced interaction overlap between the Bovine Serum Albumin (BSA) solution and terahertz waves, while minimizing the water absorption loss. Maximum frequency shift over 400 GHz around 1.2 THz under different solutions of BSA injection has been observed accordantly both in simulation and measurement. The proposed THz sensor with both high sensitivity and high signal to noise (SNR) has great potential for chemical and biochemical detection.