Terahertz spectroscopy, with the advantages of label-free and non-ionizing has been considered as a potential method for biomolecule detection. Hereby we present a promising approach for the label-free protein sensing in liquid environment. In this work, we designed a grapheme-based device to increase the accumulated amount of protein molecules in the solution. The sensor demonstrates a quick and sensitive response to HER2 proteins and gave a linearly response to the concentrations of HER2 from 63 ng/ml to 4.0 μg/mL. The results demonstrated that once HER2 molecules targeting on the surface of graphene, the conductivity of graphene was significantly changed. This provided us a potential method to detect trace biomarker within liquid phase by using terahertz spectroscopy.
Here, we proposed the thin-film total internal reflection geometry (TF-TIR) for sensitive material characterization. Equations to extract the material dielectric constant in the TF-TIR geometry was derived. The TF-TIR technique consumes less sample material and provides higher sensitivity compared with the traditional attenuated total reflection (ATR) geometry. The sensitivity of TF-TIR geometry was first investigated by simulation using a 10 μm thick α-lactose thin film as the sample. A THz microfluidic device was fabricated according to the TF-TIR design in the simulation with TOPAS and high-resistivity Si as the top and bottom plate, respectively. The reaction chamber was sandwiched between the TOPAS and Si plates. The device was placed on a right-angle Si prism to realize the total internal reflection. Water and alcohol mixtures were used to verify the sensitivity of the device. Our results demonstrate that the TF-TIR technique has the potential to improve the sensitivity in measuring the dielectric constant of biological samples with THz waves. Our design can be used for THz lab-on-chip devices.
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