Development of optically transparent, flexible and robust antennas by using conductive-mesh-polymer composites
Optically transparent and flexible antennas are becoming increasingly useful due to their potential applications in wide range of areas, especially in wireless wearable technologies where virtually imperceptible antennas are highly demanded. Concurrently, the demands for new antenna designs, new materials and realization techniques for antenna fabrication are in need to develop flexible transparent antennas using inexpensive methods. This thesis is dedicated to the development of novel transparent antennas by utilizing conductive-mesh-polymer composite which is highly transparent, flexible, robust and inexpensive. The proposed transparent conductive mesh is VeilShield from Less EMF Inc., USA and the proposed polymer is polydimethylsiloxane (PDMS), which is optically transparent, flexible, heat resistant and easily available.
The first analysis of this thesis is a detailed investigation of the morphology, optical and electrical characteristics of the flexible-mesh-polymer composite. The feasibility of the composite for the development of flexible, robust and transparent antennas has been studied by fabricating a microstrip patch antenna and measuring its RF performance in multiple times of bending cycle. After a thorough investigation of the characteristics of the composite, several antennas have been designed, analysed, fabricated and experimentally tested.
The developed first antenna is a dual-band transparent wearable antenna operating at 2.4 and 5 GHz Industrial, Scientific, and Medical (ISM) bands. The performance of the antenna has been tested in both free space and on phantoms. Moreover, for improving the gain and efficiency of the antenna, a novel approach of attaching two conductive-mesh sheets to realize the radiating patch has been demonstrated.
The second antenna is a new water-based flexible and transparent antenna, which has very high optical transparency, flexibility, robustness and good RF performance. In this design, a planar dipole radiator is backed by a water reflector to alter the bidirectional radiation pattern of the dipole to unidirectional pattern. The explored method is simple and inexpensive and is useful for the production of optically transparent, flexible, durable and low-cost antennas, as well as RF/microwave components.
The demonstrated third antenna has explored the design approach of compact and transparent wearable antennas and further investigated new methods to increase the transparency of wearable antennas by using defected ground planes. The performance of the demonstrated antennas have been measured in free space and on phantoms.
In the fourth design, a circular polarized (CP), conformal and transparent ultra-high frequency (UHF) radio frequency identification (RFID) tag antenna has been developed. The read range and axial ratio (AR) performance of the tag antenna have been measured in both at and various bending states, which show promising performance as compared to rigid opaque CP tag antennas.
After investigating four different antennas, this thesis explicitly exhibits that the proposed transparent and flexible conductive-mesh-polymer composite can be implemented for low-cost production of flexible transparent antennas and other RF devices for broad range of applications where optical transparency, flexibility and cost are prime requirements of the systems.
