Meta-Biosensor With High Q-Factor Based on Wet Etching for Terahertz Detection

Optical biosensors are the devices converting biological signals into light signals for quantitative and classification detection. In recent years, metasurfaces combined with terahertz (THz) time-domain spectroscopy have been applied in various biosensing field, such as medical sensing and food monitoring. However, current meta-sensors face the problems of complex structures and insufficient sensitivity, and target molecules categories are limited. Therefore, we proposed a meta-sensor with both reliable fabrication, simple structure, and high sensing performance. Here, the metasurface is fabricated on both rigid and flexible film, and the effect of substrate on sensing performance is the first time to be discussed experimentally. We established a novel relationship between analyte [cancer cell, doxycycline hydrochloride (DCH)] to resonance, and the sensing results are comprehensive and well-performed. In experiments, an obvious frequency shift of 110 GHz occurs when DCH concentration increased from 0.1 to 16 mg/mL, and the practical sensitivity reaches up to 166.67 kHz $\cdot $ mm2/cell for the human prostatic cancer cell DU-145 and 116.67 kHz $\cdot $ mm2/cell for human bladder cancer cell 5637, respectively. The proposed meta-sensor, with advantages of no-label, high ${Q}$ -factor, and reliable performance, not only validates the effectiveness of refractive index sensing but also provides a significant reference for high-performance THz sensors in biological sensing applications.