Mechanical Deformation of Electronic Textile Antennas: Approaches and Validation

Abstract

In this dissertation, we explore the intentional and unintentional mechanical deformation of electronic textile (e-textile antennas) as a means of either reconfiguring their performance or sustaining their original performance despite any structural changes. State-of-the-art techniques used for mechanically reconfiguring flexible antennas employ fragile conductive inks and/or copper tape. By contrast, our approach brings forward enhanced robustness and durability as attributed to the inherent strength of the e-threads. To facilitate folding along the creases while also providing Radio-Frequency (RF) performance close to that of copper, a graded embroidery process is brought forward. The grading scheme uses a density of 7 e-threads/mm on the antenna and a reduced density around the creases (as few as 1 e-thread/mm). Additionally, by embedding conductive e-threads inside programmable hard-magnetic soft substrates, we can programmably actuate the antennas using DC magnetic field. Antenna deformations that rely on magnetic actuation are a promising alternative to conventional complicated and labor-intensive reconfiguration approaches due to their design, fabrication, and operation simplicity. By embedding gls{ndfeb} particles in soft silicone and by further coating e-thread antennas with the resulting flexible material, novel prototypes are brought forward that are characterized by a programmable polarity, stable magnetic properties, untethered actuation, a response speed that cannot be captured with a high speed camera (60 frames per second), reversible deformation, light weight, and extreme mechanical/thermal tolerance. Moreover, the state-of-the-art on wearables acknowledges that flexible antennas crumple and typically recommends placement on flat body areas to eliminate deformation. Here, we propose the first folding-independent e-textile antennas which (as opposed to folding-dependent antennas) maintain their performance despite underlying deformations. We, finally, compare the RF and gls{sar} performance of folding-independent vs. folding-dependent antennas across a wide frequency range (0.915 to 5.8 GHz).