An Ultraminiaturized Terahertz Metamaterial Absorber for High-Sensitivity Label-Free Detection of Multiple Cancer Cells

Abstract

An ultrathin, compact, and flexible terahertz (THz) metamaterial absorber-based biosensor is proposed for the label-free and noninvasive detection of various carcinoma cells through refractive index (RI) sensing. The proposed sensor enhances electromagnetic field localization and light–matter interaction, thereby enabling high-performance THz cancer detection. It consists of a 0.3-<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m-thick copper resonator patterned on a 1-<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m-thick gallium arsenide (GaAs) substrate, and the proposed absorber resonates at 3.5 THz with a reflection coefficient of 30 dB, indicating effective free-space impedance matching. It achieves 99.9% absorptivity within an ultracompact unit-cell footprint of <inline-formula> <tex-math notation="LaTeX">$0.175~\lambda _{L}~\times ~~0.175~\lambda _{L}$ </tex-math></inline-formula>. Electromagnetic confinement of the surface current and e-field enhances the interaction with an analyte, leading to a sensitivity of 1.33 THz/RIU, a quality factor of 18.327, and a figure of merit (FoM) of 7.02 RIU⁻¹. The proposed biosensor provides label-free and noninvasive THz cancer diagnosis through structural simplicity, ultraminiaturization, and high sensing capabilities.