Purpose: Currently available hyperthermia technology is not well suited to treating cancer malignancies in the intact breast. This study investigates a microwave applicator incorporating multiple patch antennas, with the goal of facilitating controllable power deposition profiles for treating lesions at diverse locations within the intact breast. Materials and methods: A 3D-computational model was implemented to assess power deposition profiles with 915 MHz applicators incorporating a hemispheric groundplane and configurations of 2, 4, 8, 12, 16 and 20 antennas. Hemispheric breast models of 90 mm and 150 mm diameter were considered, where cuboid target volumes of 10 mm edge length (1 cm³) and 30 mm edge length (27 cm³) were positioned at the centre of the breast, and also located 15 mm from the chest wall. The average power absorption (αPA) ratio expressed as the ratio of the PA in the target volume and in the full breast was evaluated. A 4-antenna proof-of-concept array was fabricated and experimentally evaluated. Results: Computational models identified an optimal inter-antenna spacing of 22.5° along the applicator circumference. Applicators with 8 and 12 antennas excited with constant phase presented the highest αPA at centrally located and deep-seated targets, respectively. Experimental measurements with a 4-antenna proof-of-concept array illustrated the potential for electrically steering power deposition profiles by adjusting the relative phase of the signal at antenna inputs. Conclusions: Computational models and experimental results suggest that the proposed applicator may have potential for delivering conformal thermal therapy in the intact breast.

The microwave dielectric properties of cotton fabrics in the fabric thickness direction are investigated in relation to the fabric construction, thread count and solid volume fraction (SVF) under the five different relative humidity (RH) conditions. The dielectric constants of the fabric samples exhibits increasing trends with RH, and this is primarily due to more abundant free water in the samples. For most of woven and knitted samples, an increase in thread count results in a higher dielectric constant and this is associated with the increase in SVF. By comparing the woven and knitted samples of the same SVFs, it is found that the woven fabrics tend to have higher dielectric constants than the knitted samples at near 2.45 GHz. This observation of the dielectric properties of cotton fabrics clearly indicates that although the SVF is primarily responsible for the resulting dielectric properties of fabrics, other structural parameters must also be considered in dielectric analysis. Based on in-situ analysis of yarn orientations in the given samples, we claim that the yarn orientation plays an important role in the microwave dielectric properties of cotton fabrics.

Breast hyperthermia is a non-invasive cancer treatment, where breast temperature is mildly elevated by a localized electromagnetic (EM) irradiation to deactivate and damage cancer cells. The emerging needs associated with this medical modality include the development of a highly wearable microwave applicator with a low power requirement to enable a more patient-friendly and continuous hyperthermia therapy. As a potential solution, we propose a textile antenna that consists of a copper-plated woven polyester fabric as a radiating patch and a ground plane and a woven polyester fabric as a dielectric substrate and a padding layer. The porous nature of these textile materials enables construction of a lightweight and flexible antenna with a low dielectric loss for a more comfortable hyperthermia treatment. By incorporating a synthetic breast tissue for a model study, the temperature rises were measured to be 3.3 °C and 1.9 °C at 5 mm and 15 mm depths, respectively, after 15 min of heating (input power of 1 W). This suggests that the textile-based approach could be an effective solution for comfortable and long-term applications of breast hyperthermia therapy.

With the development of smart and multi-functional textiles, conductive yarns are widely used in textiles. Conductive yarns can be incorporated into fabrics with traditional textile techniques, such as weaving, knitting and sewing. The electromechanical properties of conductive yarns are very different from conventional yarns, and they also affect the processability during end-product manufacturing processes. However, systematic evaluation of the electromechanical properties of commercial conductive yarns is still elusive. Different conductive materials and production methods for making conductive yarns lead to diverse electromechanical properties. In this work, three types of conductive yarn with different conductive materials and yarn structures were selected for electromechanical characterization. A total of 15 different yarns were analyzed. In addition, the change of resistance with strain was tested to simulate and predict the possible changes in electrical properties of the yarn during weaving, knitting, sewing and other end uses. It was found that Metal-based yarns have good electrical properties but poor mechanical properties. The mechanical properties of Metal-coated yarns are similar to conventional yarns, but their electrical properties are relatively poor. The data shown in this research is instructive for the subsequent processing (weaving, knitting, sewing, etc.) of yarns.

A fabrication and characterization procedure is detailed for a flexible planar antenna integrated into textiles by interfacing thin metal-coated fabric sheets on a polyester fabric substrate. From the full-wave electromagnetic simulations and measurements, it is observed that the low dielectric dissipation in the porous woven polyester enables the fabric antenna to achieve a high gain of 8.4 dBi. It is comparable to other antennas fabricated with engineered substrates of low-loss polymer composites. Using this antenna, the impact of cylindrical concave bending deformation is observed in terms of the impedance matching and radiation performance. The simulated and measured results agree reasonably well. A 1.2% frequency shift is observed when the antenna is bent concavely along its length, while bending along its width showed only a marginal impact. On the other hand, the gain is reduced by as much as 1.0 and 0.5 dB when the antenna is bent along its length and width, respectively. The impact of padding layers was also investigated when placed above the radiating patch and below the ground plane. Because the textile padding layers have complex permittivity closer to air due to their highly porous structure, it is expected to observe only small influence on the radiation performance. However, the simulations and measurements show that padding the radiating patch lowers both the operating frequency and the realized gain by up to 1.6% and by up to 0.9 dB, respectively, due to dielectric loading and dissipation.