Patterned graphene and terahertz metasurface-enabled multidimensional ultra-sensitive flexible biosensors and bio-assisted optical modulation amplification

Abstract

Although terahertz metasurface-enabled biosensors focus on current research, reports of multidimensional ultra-sensitive detection in the terahertz (THz) regime are rare. Here, we present a novel flexible THz biosensor that consists of electromagnetic-induced transparency-like metasurfaces and patterned graphene, which is used for the multidimensional ultra-sensitive detection of plant protein. Based on changes in frequencies and amplitude, the proposed biosensor could detect plant protein molecules with a 42.3 pg/ml limit. The internal mechanism can be explained by the positive impact of plant proteins on the dielectric environment. As plant protein concentration increases and covalent bonding of the patterned graphene strengthens, the Fermi level of graphene moves to the Dirac point, and the conductivity of graphene correspondingly decreases. As a result, we observed marked enhancement of the transmission amplitude and all frequency point shifts. We also show results for fitting the coupled harmonic oscillator model and theoretical analysis of the changes of graphene Fermi level to explain the sensing mechanism. In addition, we successfully achieved biological-assisted optical modulation amplification under laser excitation. This work may provide a new strategy for applying terahertz metasurfaces in the field of biosensing.