Abdul Jabbar

Terahertz spectral region, as a part of the electromagnetic spectrum, is an emerging field of technology for a future generation biomedical sensing applications thanks to the strong sensitivity to water, and its non-ionizing nature that guarantees safety for repeated uses on biological tissues. In this work, we propose a dual-band, tunable metasurface biosensor based on graphene that could be used for early in-vivo skin cancer detection. The sensor is designed to operate at two resonance frequencies: 1.092 THz and 3.18 THz. The double Debye framework was used to model optical properties of basal cell carcinoma (BCC). The sensor's performance on the test sample showed a full width half maximum (FWHM) of 48 GHz and a resonance shift of 36 GHz. The sensitivity, figure of merit (FOM), detection limit and quality factor (Q) are found to be 0.2389 THz/RIU, 4.93 RIU⁻¹, and 21.7, 0.19 RIU respectively. Tunability of the sensor is obtained by varying graphene’s chemical potential or Fermi voltage from 0.8 to 1 eV. The design of biosensor was simulated in CST Microwave Studio, and its equivalent circuit model was developed. Thus, the numerically simulated results of the biosensor under sample testing confirm that the proposed design can be considered a label free promising candidate for THz biosensing applications.

This manuscript demonstrates a comprehensive analysis of a low-profile dual-band flexible omnidirectional wearable antenna, designed for Wireless Body Area Network (WBAN) applications. The proposed antenna is designed and fabricated on a commercially available semiflexible RT/duroid 5870 substrate. The antenna prototype is composed of a circular radiating patch with a star-shaped slot at the center, providing dual-band operations that resonates at the 2.45 GHz ISM band and 5.2 GHz WLAN band. Meanwhile, two truncated arc-shaped slots at the top and bottom edges of the radiating patch and the partial ground were utilized to improve the reflection coefficients (S ₁₁ ) and impedance bandwidth of the antenna. The proposed antenna has a compact footprint of 47×30×0.787 mm ³ (0.38 λ0 × 0.25 λ0 × 0.006 λ0 at 2.45 GHz), with measured impedance bandwidth of 48% and 38.5% at 2.45 GHz and 5.2 GHz respectively. Moreover, the designed antenna has an omnidirectional and bidirectional radiation feature with the estimated gain of 2.5 dBi, 4.63 dBi and numerical efficiencies of 98.5% and 95% at 2.45 GHz and 5.2 GHz respectively. Furthermore, a comprehensive investigation encompassing a specific absorption rate and an exploration of bending aspects validated the effectiveness of the suggested design in adhering the SAR threshold and its remarkable robustness, when confronted with the demands imposed by human body loading and structural deformations. Consequently, both the numerical and measured results strongly endorse the significance of the suggested design for lightweight, body-worn wearable devices within the Wireless Body Area Network applications.

Broadband Terahertz (THz) metamaterial absorbers with tunable absorption characteristics have been attracting a lot of attention due to their high demand and utilization in advanced optical systems. Therefore, we propose a single-layer graphene-supported metamaterial absorber with a combination of square, circular and cross-shaped meta-resonators, exhibiting an outstanding absorption of more than 90% from 2.3 THz to 6.4 THz. The overall size of the unit cell is 15 × 15 μm ² , which holds graphene-based meta-resonators etched over a lossy dielectric substrate, backed by a 0.2 μm thick gold as a perfect reflector. This design architecture achieves the ultra-broadband absorption features by continuous design evaluation and optimization. The graphene-based metamaterial absorber (GMMA) reveals a polarization-insensitive response, and it also provides above 70% absorption for obliquely incident angles over the large operating bandwidth (2.3-6.4 THz). The polarization conversion ratio (PCR) also approached zero over the wideband of 4.1 THz and its maximum value of 16% was recorded at 4 THz. Furthermore, the amplitude spectra of the proposed GMMA is modulated from 19% to above 90% by stimulating the chemical potential of graphene from 0 eV to 0.7 eV. The simplified design configuration, broadband absorption features, and tunable capability of the GMMA provide the pathway to develop high-speed optical switches, THz detectors, and other opto-electronic devices