3D-printed thermoplastic polyurethane for wearable breast hyperthermia

Microwave breast hyperthermia is a class of cancer treatment, where breast temperature is elevated by a focused electromagnetic (EM) radiation to impair cancer cells. While the current mainstream in microwave breast hyperthermia is centered on bulky and rigid systems, wearable antennas would offer considerable benefits such as superior conformity to individual patient anatomy and better comfort. In this proposition, this paper presents 3D-printed flexible antenna prototypes for wearable breast hyperthermia applications. Since the dielectric properties are expected to dominate the antenna gain but could be influenced by the solid volume percentage, this work first investigates the relationship between the dielectric properties and solid volume percentage of a 3D-printed flexible filament. From this, it is found that with decrease in the solid volume percentage, the dielectric constant decreases following the classic theory of dielectric mixture. Based on this observation, optimal antennas are designed for substrates in different infill levels by running a 3D full-wave EM simulator and fabricated by 3D printing a polyurethane filament. Temperature elevations in a synthetic breast tissue are measured by a thermometer and are ~ 5.5 °C and ~ 3.2 °C at the 5 mm- and 7 mm-deep locations, respectively. The infill percentage makes little difference in the heating efficacy. Based on these findings, this translational study sheds light on the possibility of wearable breast hyperthermia with the 3D-printed flexible and conformal antennas.

Synthesis of High Directivity Beams for Conformal Sources

<p>The<b> </b>role of the source geometry in the the radiation of focusing beams by conformal antennas is examined by the comparison of their directivity functions at different maximum directions. An inverse source problem approach is adopted, where solutions stable with respect to data uncertainties are to be found by relying on the analysis of the pertinent operator by the Singular Values Decomposition. This general framework allows to connect the mean value of the mazimum directivity function to the Number of Degrees of Freedom of the conformal source, which depends only on its electrical length. For each source geometry the focusing far field ensuring the maximum directivity for every pointing direction and the corresponding source current are obtained. The comparison with the ones achieved by the usual phase compensation technique of the source current reveals their optimal behavior. The usefulness of the approach as a tool in antenna synthesis is shown by comparing different geometries for those applications where identical beams are required to be rdiated for the coverage of a larga angular domain.</p>

Synthesis of High Directivity Beams for Conformal Sources

<p>The<b> </b>role of the source geometry in the the radiation of focusing beams by conformal antennas is examined by the comparison of their directivity functions at different maximum directions. An inverse source problem approach is adopted, where solutions stable with respect to data uncertainties are to be found by relying on the analysis of the pertinent operator by the Singular Values Decomposition. This general framework allows to connect the mean value of the mazimum directivity function to the Number of Degrees of Freedom of the conformal source, which depends only on its electrical length. For each source geometry the focusing far field ensuring the maximum directivity for every pointing direction and the corresponding source current are obtained. The comparison with the ones achieved by the usual phase compensation technique of the source current reveals their optimal behavior. The usefulness of the approach as a tool in antenna synthesis is shown by comparing different geometries for those applications where identical beams are required to be rdiated for the coverage of a larga angular domain.</p>

Inverse Source on Conformal Conic Geometries

This manuscript has been accepted for publication on IEEE Transactions on Antennas and Propagation.<br><br><div>Abstract:</div><div>The paper adopts an inverse problem approach to examine the role of some 2D geometries in the source reconstruction from far zone data. It aims at evaluating the number of independent pieces of information, i.e. the number of degrees of freedom (NDF), of the source and pointing out the set of far zone fields corresponding to stable solutions of the inverse problem. Some of the results are relevant to the synthesis problem of conformal antennas, since a general comparison of different source geometries in providing radiation pattern specifications is proposed.</div>

Inverse Source on Conformal Conic Geometries

This manuscript has been accepted for publication on IEEE Transactions on Antennas and Propagation.<br><br><div>Abstract:</div><div>The paper adopts an inverse problem approach to examine the role of some 2D geometries in the source reconstruction from far zone data. It aims at evaluating the number of independent pieces of information, i.e. the number of degrees of freedom (NDF), of the source and pointing out the set of far zone fields corresponding to stable solutions of the inverse problem. Some of the results are relevant to the synthesis problem of conformal antennas, since a general comparison of different source geometries in providing radiation pattern specifications is proposed.</div>

Recent Developments and State of the Art in Flexible and Conformal Reconfigurable Antennas

Reconfigurable antennas have gained tremendous interest owing to their multifunctional capabilities while adhering to minimalistic space requirements in ever-shrinking electronics platforms and devices. A stark increase in demand for flexible and conformal antennas in modern and emerging unobtrusive and space-limited electronic systems has led to the development of the flexible and conformal reconfigurable antennas era. Flexible and conformal antennas rely on non-conventional materials and realization approaches, and thus, despite the mature knowledge available for rigid reconfigurable antennas, conventional reconfigurable techniques are not translated to a flexible domain in a straight forward manner. There are notable challenges associated with integration of reconfiguration elements such as switches, mechanical stability of the overall reconfigurable antenna, and the electronic robustness of the resulting devices when exposed to folding of sustained bending operations. This paper reviews various approaches demonstrated thus far, to realize flexible reconfigurable antennas, categorizing them on the basis of reconfiguration attributes, i.e., frequency, pattern, polarization, or a combination of these characteristics. The challenges associated with development and characterization of flexible and conformal reconfigurable antennas, the strengths and limitations of available methods are reviewed considering the progress in recent years, and open challenges for the future research are identified.

Radiation of a Circular Arc Source in a Limited Angle for Non-uniform Conformal Arrays

Conformal antennas lack of general analysis methods of their radiation properties. For a circumference source, we examine the role of the angular width of the observation domain both in far and near zone in determining the set of radiated fields. By an inverse problem approach, the evaluation of the number of independent pieces of information, i.e. the number of degrees of freedom (NDF), and the analysis of the reconstructions of point-like sources allow to introduce optimal array configurations. The results are relevant to the radiation pattern synthesis problem and to array diagnostics applications.

Radiation of a Circular Arc Source in a Limited Angle for Non-uniform Conformal Arrays

Conformal antennas lack of general analysis methods of their radiation properties. For a circumference source, we examine the role of the angular width of the observation domain both in far and near zone in determining the set of radiated fields. By an inverse problem approach, the evaluation of the number of independent pieces of information, i.e. the number of degrees of freedom (NDF), and the analysis of the reconstructions of point-like sources allow to introduce optimal array configurations. The results are relevant to the radiation pattern synthesis problem and to array diagnostics applications.