A terahertz (THz) metamaterial biosensor based on four identical resonators is experimentally demonstrated, and high sensitivity is achieved by exciting four synchronous inductor-capacitor oscillations in a unit cell. The effect of geometries on the resonance frequency of the sensor is investigated using the finite integration time domain method, and the simulated sensitivity is 85 GHz per refractive index unit. The biosensor sample is fabricated using a surface micromachining process and characterized by a THz time domain spectroscopy system combined with bovine serum albumin (BSA) solution as an analyte. The experimental results indicate that the resonance frequency shows distinct redshift when the concentration of BSA solution increases. When the concentration is high, up to 765 µ mol l ⁻¹ , the frequency shift reaches 50 GHz, and the measurable minimum concentration is low, down to 1.5 µ mol l ⁻¹ . The biosensor is small in shape, wide in measurable range, convenient in operation, and rapid in detection, which is of great significance for rapid concentration measurement, biomolecules detection, and disease diagnosis.

Electrocardiogram (ECG) signal evaluation is routinely used in clinics as a significant diagnostic method for detecting arrhythmia. However, it is very labor intensive to externally evaluate ECG signals, due to their small amplitude. Using automated detection and classification methods in the clinic can assist doctors in making accurate and expeditious diagnoses of diseases. In this study, we developed a classification method for arrhythmia based on the combination of a convolutional neural network and long short-term memory, which was then used to diagnose eight ECG signals, including a normal sinus rhythm. The ECG data of the experiment were derived from the MIT-BIH arrhythmia database. The experimental method mainly consisted of two parts. The input data of the model were two-dimensional grayscale images converted from one-dimensional signals, and detection and classification of the input data was carried out using the combined model. The advantage of this method is that it does not require performing feature extraction or noise filtering on the ECG signal. The experimental results showed that the implemented method demonstrated high classification performance in terms of accuracy, specificity, and sensitivity equal to 99.01%, 99.57%, and 97.67%, respectively. Our proposed model can assist doctors in accurately detecting arrhythmia during routine ECG screening.

An antibody modified terahertz (THz) metamaterial biosensor is proposed to detect the concentration of carcinoembryonic antigen (CEA). The biosensor has four metal split-ring-resonators (SRR) in a unit cell. The finite integration time domain (FITD) method is used to design and optimize the structure. The simulation shows that the biosensor is insensitive to incident angles and the sensitivity reaches to 76.5 GHz/RIU (Refractive Index Unit). The sample is manufactured using a surface micromachining process and characterized by a THz time domain spectroscopy (THz-TDS) system. The experimental results indicate that the resonant frequency of the biosensor decreases with the increase of the concentration of analytes on the surface. After that, the biosensor is modified with anti-CEA and used to detect the concentration of the CEA. Interestingly, the response of the biosensor depends heavily on the concentration of the Anti-CEA modified on the surface of the biosensor. When the concentration of Anti-CEA is 20 ng/ml, the resonant frequency shift shows good linearity to the concentration of CEA and the limit of detection (LOD) reaches to 0.1 ng/ml. This study paves a new way for sensitively detection of biomolecules, cancer biomarkers and immune responses, which is important for early stage diagnosis of cancers.

We propose a simple method for fast and label-free identification of early-stage cervical cancerous tissues using a metamaterial (MM) terahertz (THz) biosensor with two resonant absorption frequencies at 0.286 THz and 0.850 THz, respectively. Because the two resonant absorption frequencies are very sensitive to the ambient change of dielectric properties, the cervical cancerous tissues can be distinguished from the normal tissues by analyzing the resonant frequency shift. The calculated sensitivity of the low resonant frequency and that of the high resonant frequency are 29 and 74 GHz/RIU, respectively. In the experiment, the cervical cancerous tissue samples were taken from different patients, and the cancerous and normal parts were determined by hematoxylin-eosin (HE) stain. Compared with the traditional method of directly detecting cancer tissue without the sensor, this method has the advantages of being simple, label free and fast. In addition, compared with biosensors which have a single resonant absorption frequency, the biosensors with double resonant absorption frequencies have higher accuracy. This method potentially can be applied for the detection and diagnosis of many other cancer tissues.

Actively controlling the amplitude and phase of terahertz (THz) wave is of great significance for THz broadband wireless communication and high-resolution THz imaging. In this paper, we present a THz amplitude and phase modulator based on electrically triggered vanadium dioxide (VO ₂ ) reconfigurable metasurface. The unit cell of the device consists of three concentric split-rings-rings (SRRs) on the sapphire substrate, i.e., one VO ₂ -split-ring (VSR) and two metal SRRs. The VSR is embedded between two metal SRRs. The resonance mode, resonance intensity and surface current distribution in the unit cell can be dynamically manipulated by electrically triggering the insulator-to-metal-transition (IMT) of the VO ₂ . The sample is fabricated using a surface micromachining process and characterized by a THz time-domain-spectroscopy (TDS) system. The experimental results show that, 90 degrees phase shift is achieved in a broad bandwidth of 70 GHz. Meanwhile, the amplitude modulation depth reaches 71% at 0.79 THz. The transmission and the phase shift are calculated by an equivalent circuit model, and simultaneously simulated using a full-wave circuit simulation software based on the Method of Moments (MoM). The calculation and simulation results agree with the experimental results. The device has potential applications in THz imaging, broadband wireless communications and array phase controlling.