Integer-PSO-Optimized Checkerboard Dual-Band Terahertz Metamaterial Absorber for Biomedical Sensing Applications

This paper presents a checkerboard-patterned terahertz (THz) metamaterial absorber engineered for wide-band, dual-band absorption. The absorber consists of a gold metal layer patterned on a polyimide substrate, forming a unit cell structure with dimensions of 85 µm × 85 µm. At the core of the design is a square metal patch of 67 µm × 67 µm, which is divided into a 5 × 5 grid of 25 smaller cells. An integer-coded Particle Swarm Optimization (PSO) algorithm is employed to generate the pattern, where an input value of ‘1’ retains the metal in a cell, and a ‘0’ results in the removal of metal from that cell, resulting in a digitally optimized checkerboard pattern. The substrate height is also optimized and fixed at 7 µm to enhance resonance characteristics. The PSO algorithm is run for 50 iterations, with the fitness function defined as the number of frequency points at which the absorption exceeds 90%. The finalized design achieves two distinct absorption peaks with high efficiency: 99.53% at 3.434 THz, with a 90% absorption bandwidth of 212 GHz; and 99.35% at 3.823 THz, with a bandwidth of 177 GHz. While the absorption performance is already significant, it can be further improved by increasing the number of PSO iterations, albeit at the cost of higher computational complexity. The proposed absorber demonstrates strong potential for biomedical sensing, as validated through its ability to differentiate between cancerous and non-cancerous breast and blood cells. This work paves the way for fully automated, algorithm-driven metamaterial design strategies in the THz regime, particularly for applications in non-invasive biomedical diagnostics.