Design and characterization of a cotton fabric antenna for on-body thermotherapy

As a non-invasive therapeutic modality, microwave hyperthermia has gained increasing prominence in recent breast cancer research. In microwave hyperthermia, the temperature of a cancerous lesion is raised to 39–45°C by microwave irradiation to shrink tumors. Currently available applicators in clinics are aperture antennas (or waveguides) that are bulky and stationary; as such, patients are required to stay in an uncomfortable position for an extended period of time. On this account, this paper introduces the design and characterization of a novel cotton fabric antenna for a truly wearable and patient-friendly breast hyperthermia therapy. The developed antenna, consisting of cotton and copper-plated polyester fabrics, offers flexibility, tenacity, moisture-absorbing properties and breathability desirable for potential integration into intimate apparel. On the other hand, the use of cotton fabric brings about a major concern: moisture is documented to alter the dielectric properties of cotton fabrics and hence could impact the antenna performance. Therefore, for the purpose of concept and design validation, this research investigated the impedance matching and heating performance at three levels (20%, 65% and 80%) of relative humidity (RH). From both simulations and measurements, the RH was found to shift the resonant frequency slightly, but did not critically affect the impedance matching and the heating performance – the measured temperature rises were 4.7–4.9°C and 2.3–2.5°C at the depths of 5 mm and 15 mm, respectively. These theoretical and experimental insights cast light on the feasibility and benefits of moisture-absorbing, cotton-based medical textiles for administration of highly patient-friendly breast hyperthermia.