Background
Metasurfaces, as 2D artificial electromagnetic materials engineered at subwavelength scales, enable efficient manipulation of electromagnetic waves far beyond natural materials, bridging the gap between fundamental photonics and real-world technologies. They exhibit prominent application potential in two core fields: terahertz (THz) biosensing and microwave wireless communications，as shown in Fig.1 and Fig2.
In THz biosensing, THz waves (0.1–10 THz) possess unique advantages of non-ionizing nature (meV-level photon energy), rich molecular fingerprint information, and good penetration, making them ideal for label-free, non-destructive detection of biological samples (e.g., biomolecules, cells, tissues). However, traditional THz sensing faces critical challenges: low response efficiency of natural materials in the THz band, mismatch between THz wavelengths and trace biomolecule sizes (leading to weak light–matter interaction), severe absorption of THz waves by water (interfering with aqueous sample detection), and limitations of metal-based THz metasurfaces (e.g., large ohmic loss, poor biocompatibility, limited tunability). These issues restrict the sensitivity, specificity, and practicality of THz biosensors.
In microwave wireless communications, with the accelerated development of 5G and the ongoing research of 6G, modern communication systems confront urgent challenges including spectrum scarcity, complex channel conditions (e.g., multipath interference, non-line-of-sight transmission), and energy efficiency bottlenecks. Conventional devices like phased array antennas rely on numerous phase shifters, resulting in high power consumption, high cost, and complex hardware. Additionally, traditional building materials (e.g., low-emissivity glass) shield microwave signals, and static device designs fail to adapt to dynamic communication scenarios, all of which hinder the performance enhancement and intelligent upgrading of communication systems.
Research Progress
To address the above challenges, the research team (led by Yue Wang et al.) systematically reviewed the latest advances in metasurface technologies for THz biosensing and microwave wireless communications, with key findings as follows:
1. Metasurface Applications in THz Biosensing
The team focused on four representative material platforms and three functional strategies to optimize THz biosensing performance:
Metal-based THz metasurface biosensors: Leveraging mature fabrication processes and flexible structural designs, they support resonance modes like spoof localized surface plasmons, toroidal dipole mode, and quasi-bound states in the continuum (QBIC). For example, a toroidal dipole resonance-based biosensor detected glioma cell subtypes with polarization insensitivity at 2.12 THz; a metamaterial chip with resonance frequencies of 1.16, 1.64, and 2.07 THz achieved sensitive detection of SARS-CoV-2 spike protein-derived peptides, with a detection limit of ~0.1 mg/ml (41.7 μM) and R² > 0.98 for concentration-dependent responses. QBIC-based metal metasurfaces (e.g., 2-ring chain resonators) achieved a detection limit of 12.5 pmol/μl for homocysteine, 40 times higher than dipole modes.
Graphene–metal composite THz metasurface biosensors: Graphene’s high electron mobility and electric tunability enhance sensor performance. A graphene-assisted electromagnetically induced transparency (EIT)-like sensor detected ovalbumin (OVA) with a limit of detection (LoD) of 8.63 pg/ml; a graphene metasurface integrated with quasi-electrode resonance distinguished sodium benzoate and potassium sorbate, achieving LoDs of 0.12 fg/ml and 0.23 pg/ml, respectively. Combining graphene with gold nanoparticles (AuNPs) further improved sensitivity, e.g., an aspartic acid sensor with a LoD of 10.48 fg/ml, and a circulating tumor DNA (ctDNA) sensor with a LoD of 0.22 fM (capable of distinguishing single-nucleotide mismatches).
CNT film-based THz metasurface biosensors: Carbon nanotubes (CNTs) exhibit high conductivity, large specific surface area, and good biocompatibility. An anisotropic multi-walled CNT (MWCNT) metasurface detected 2,4-dichlorophenoxyacetic acid (2,4-D) and chlorpyrifos with a minimum detectable mass of 10 ng and sensitivities of 1.38×10⁻² /ppm and 2.0×10⁻³ /ppm, respectively. A single-walled CNT (SWCNT) metasurface modified with sulfuric acid and AuNPs detected serum amyloid A (SAA) with a sensitivity of 37.5 GHz/fM and a LoD of 0.1 fM; carboxylated SWCNTs functionalized with d/l-cysteine enabled chiral detection of d/l-tartaric acid.
All-dielectric THz metasurface biosensors: Featuring low loss and high quality (Q)-factor, they include silicon gratings (detecting chlorpyrifos with a sensitivity of 414 GHz/RIU and a LoD of 20–100 ppt), silicon pillar arrays (detecting tumor markers CA125 and HER2 with LoDs of 1 ng/ml and 0.1 ng/ml, respectively), and lithium tantalate triangular prisms (detecting cinnamoylglycine with a LoD of 1.23 μg/cm²). Integrating functionalized AuNPs enhanced specificity, e.g., an HA antigen sensor with a sensitivity of 2.96 GHz·ml/nmol (2.66 times higher than unmodified systems) and a LoD of 1.05 nmol/ml.
Functional strategies: Label-free refractive index sensing (simple, real-time but sensitive to environment), specific molecular recognition (via antibodies, aptamers, or hydrogels to improve selectivity), and pixelated metasurface-based fingerprint spectral reconstruction (exploiting molecular vibrational/rotational modes for structural isomer identification). For instance, a frequency-selective fingerprint sensor (FSFS) enhanced broadband absorption of chiral carnitine (0.95–2.0 THz) with an enhancement factor of ~7.3 and realized narrowband AIT (absorption-induced transparency) for α-lactose.
2. Metasurface Applications in Microwave Wireless Communications
The team summarized the evolution of microwave metasurfaces into three stages—manufacturing feasibility, programmable control, and multifunctional integration—and highlighted key technical breakthroughs:
Low-cost wireless communication devices: Cost-effective fabrication techniques (printed circuit boards, 3D printing, laser direct writing) enabled large-area/flexible metasurfaces. A metasurface lens array (MLA) reduced the focal length to 1/3 and used only 3 phase shifters for a 7.2λ₀ aperture; a 3D-printed broadband millimeter-wave lens antenna achieved a peak gain of 18.3 dBi and a 38% 10-dB impedance bandwidth. An origami metamaterial (0.125-mm PET substrate, 20-nm ITO film) realized ultrawideband reflection modulation (4.96–38.8 GHz) with an average modulation depth of 11.53 dB and >87.2% visible transmittance. Metasurface glass (3-layer structure: LIREL, air gap, MTFSS) achieved >70% transmittance in the 2.75–4.8 GHz (5G sub-6 GHz) band, resolving the trade-off between energy efficiency and communication performance of traditional Low-e glass.
Reconfigurable metasurfaces (RIS/IRS): Programmable reflecting surfaces dynamically controlled electromagnetic waves. A 5.8 GHz RIS with 1100 elements provided a 26-dB power gain; an angle-insensitive 3-bit RIS maintained stable phase shifts over 0°–60° incidence. An intelligent programmable omni-surface (IOS) supported reflection, transmission, and duplex modes, enabling full-dimensional communication. Time-domain digital coding metasurfaces realized QPSK modulation for high-data-rate video transmission; space–time coding metasurfaces achieved space-division and frequency-division multiplexing (transmitting distinct images to multiple users). A massive backscatter communication (MBWC) system modulated 2.4-GHz Wi-Fi signals, realizing 3-channel QPSK transmission with high SNR.
Multifunctional integrated metasurfaces: A dual-band phase-coded metasurface switched communication protocols for unmanned systems/satellite links; an amplifying programmable metasurface (APM) enabled simultaneous wireless information and power transfer (SWIPT), powering LEDs and transmitting videos. A holographic MIMO system based on programmable digital coding metasurfaces (PDCM) reduced costs by 50% and achieved a dual-channel QPSK transmission with an effective degree of freedom (EDoF) of 2.16. A time-varying polarization conversion metasurface operated stably at 3.7–5.1 GHz, supporting multi-user beamforming and BPSK-based high-speed data transmission. A 30×30 unit programmable millimeter-wave base station for 6G achieved ±70° beam scanning and ~23 dBi gain.
Communication-sensing integration: A spatiotemporal coding metasurface (STCM)-based integrated sensing and communication (ISAC) system optimized resource allocation, with DOA estimation error <3% and BER <10⁻³ for QPSK signals. An intelligent metasurface robot (I2MR) combined computer vision and CNN for target tracking and real-time communication; a multifunctional RIS (20×20 units, 0.8λ thickness) enhanced signals by 8 dB at 15–21 GHz and detected background objects via frequency-spatial diversity.
Future Prospects
1. THz Biosensing
Improve system detection stability: Optimize metasurface material selection, microstructure design, fabrication processes, and THz-TDS system stability to mitigate resonance drift caused by fabrication errors and environmental disturbances.
Develop dynamically tunable and specific sensors: Introduce external stimuli (electric/thermal/optical/mechanical) for active resonance regulation, enabling multi-channel, multi-index detection; advance antibody-modified interfaces, molecular absorption enhancement, and fingerprint reconstruction to upgrade from label-free sensing to high-sensitivity specific recognition.
Build intelligent sensing systems: Deeply integrate AI and deep learning into metasurface design (microstructure optimization) and data processing (signal denoising, feature extraction, concentration prediction), forming an automatic closed loop of "structure design–signal acquisition–data analysis–analyte identification" to promote intelligence and practicality.
2. Microwave Wireless Communications
Overcome hardware imperfections: Develop low-cost, high-precision, low-loss RIS units to address non-ideal phase shifts, unit coupling, and manufacturing errors, shifting focus from theoretical limits to practical deployment.
Validate real-world performance: Establish standardized testing platforms and strengthen interdisciplinary collaboration to verify metasurface performance in complex scenarios (e.g., dynamic user movement, harsh environments).
Advance high-integration systems: Integrate power amplifiers, adaptive control modules, and ambient wave modulators into RIS for multi-functionality; exploit time/space-division multiplexing and beamforming encryption to enhance physical-layer security, positioning RIS as a programmable infrastructure element for efficient, secure, intelligent 6G systems.
Construct intelligent sensor networks: Integrate vision, acoustics, and electromagnetic sensing for robust perception and collaborative decision-making; leverage deep learning for autonomous learning and dynamic control, enabling large-scale environmental perception and intelligent control.
Metasurface technologies, by bridging THz biosensing and microwave communications, are poised to drive innovations in biomedical diagnostics, 6G networks, IoT, and beyond, becoming a core platform for integrating biological and engineering systems.
The complete study is accessible via DOI:
10.34133/research.0820