Flexible Graphene Sheet Loaded Curved Patch Applicator for Superficial Hyperthermia Treatment Planning Utilizing Ripple Effect of Armchair and Zigzag Bending

Abstract

Background: Non-invasive microwave hyperthermia approaches suffer from several limitations, such as maximum energy localization in the target tissue, reduced unwanted hotspots, less penetration time at specific penetration depth, and maximum directivity of applicators. For conformal body structures, curved patch applicators avoid mismatch losses and provide circular polarization to achieve maximum power deposition at the target tissue. At microwave frequencies, graphene also exhibits good absorption properties and utilizing graphene strips on both sides of a curved patch offers potential benefits of enhancement of gain, directional radiation pattern, and suppressed sidelobes. Objective: Designing a flexible graphene sheet-loaded curved patch for a non-invasive microwave hyperthermia applicator resonating at 2.45 GHz is the prime objective of current work. The proposed work is based on utilizing the absorbing properties of graphene sheets with hybrid hexagonal boron nitride (hBN) under various bending conditions on both sides of a curved patch. Methods: Graphene-loaded curved design offers structural flexibility due to the presence of ripples on the surface and their alignment in armchair configuration (ARC) and zigzag configuration (ZGC). The bending flexibility along the two configurations alters the electronic properties and opens the band gap. Thus, the FEM model has been developed for coupling bio-electromagnetic problems of human body phantom with graphene-loaded curved patch applicator by bending it in two different configurations. Results: For both ARC and ZGC antenna design, parameters, such as return loss and realized gain, have been investigated. The proposed design achieved a maximum return loss value of -30 dB and gain of 7.1 dBi for ARC configuration since it provides the maximum difference in valance band and conduction band in band gap structure, while these values are relatively less in the case of ZGC. The implementation of the design on cylindrical body phantom is realized for ARC with a maximum Efield value of 80.2 V/m at a maximum penetration depth of 40 mm. Further simulations are performed for evaluation of penetration time and fractional tissue damage due to necrosis, and it has been observed that 10 W of input power is sufficient to achieve maximum temperature range and tissue necrosis in a duration of 15 minutes. Conclusion: The results show that a curved graphene patch applicator provides a potential solution for targeted heating in hyperthermia applications.