# Direct-Write Spray Coating of a Full-Duplex Antenna for E-Textile Applications
## 4 Conclusions  
In this work, a flexible textile-based full-duplex antenna that employs both knit and nonwoven fabrics was demonstrated. The dielectric constant of the flexible knit fabric assembly was enhanced by a direct-write spray coating of BT nanoparticle dielectric ink, making it suitable for integration into a textile-based antenna. This has demonstrated the potential of using BT dielectric ink and spray coating to manipulate the dielectric properties of porous materials. The resultant flexible antenna is dual-mode (i.e., able to simultaneously operate in transmit and receive modes with very high isolation), is robust to bending, and exhibited a gain of 9.12 dB, which is better than typical textile antennas. The textile antenna in this work shows great promise for use as a multifunctional flexible antenna in E-textile systems. In future studies, we propose exploring additional knit structures that can further reduce the porosity of this layer as well as more dielectric nks, which can aid in increasing the dielectric constant beyond what is reported in this work. In terms of manufacturing, we also propose the use of alternative direct ink writing technologies, such as inkjet printing, in order to enable more customized design. Finally, the incorporation of these devices into textile panels that can be easily implemented in standard cutting and sewing processes would enable their application. The following are available online at [[http://www.mdpi.com/2072-666X/11/12/1056/s1](http://www.mdpi.com/2072-666X/11/12/1056/s1)]([http://www.mdpi.com/2072-666X/11/12/1056/s1](http://www.mdpi.com/2072-666X/11/12/1056/s1)): Figure S1: Images of radiation measurements in an anechoic chamber: (a) front view and (b) side view, Figure S2: Schematic diagram of the experimental setup for the antenna radiation test. Conceptualization, J.S.J. and Y.Z. ; methodology, Y.Z., S.S., I.K., Y.W., D.H.W., and H.S., software, S.S.; formal analysis, Y.Z., S.S., B.M.L., I.K., Y.W., H.S., D.H.W., and J.S.J. ; writing--original draft preparation, Y.Z. and S.S.; writing--review and editing, B.M.L., I.K., Y.W., H.S., D.H.W., and J.S.J. ; supervision, J.S.J. and D.H.W. All authors have read and agreed to the published version of the manuscript. This study was supported by the US National Science Foundation through the Nanosystems Engineering Research Center for Advanced Self-Powered Systems for Integrated Sensors and Technologies under Grant EEC 1160483. The authors thank [PERSON] and Professor [PERSON] for the assistance in the SPDR test. This work was performed in part at the Analytical Instrumentation Facility (AIF) at North Carolina State University, which was supported by the State of North Carolina and the National Science Foundation (Award No. ECCS-1542015). The AIF is a member of the North Carolina Research Triangle Nanotechnology Network (RTNN), a site in the National Nanotechnology Coordinated Infrastructure (NNCI). The authors also acknowledge the US Department of Defense (DoD) and the Air Force Research Laboratory (AFRL) for provision of the Science, Mathematics, and Research for Transformation (SMART) scholarship to [PERSON]. The authors declare no conflict of interest.