Development of Robust Transparent Conformal Antennas Based on Conductive Mesh-Polymer Composite for Unobtrusive Wearable Applications

© 1963-2012 IEEE. In this paper, a detailed investigation of the realization of conformal wearable transparent antennas by integrating conductive mesh with polymer has been presented. The proposed realization method is much simpler and more cost-effective than the existing realization methods of transparent antennas, and the prototype fabricated from the selected composite materials is more flexible and robust in bending operations than other transparent antennas. In this paper, the mechanical, electrical, and optical characteristics of the proposed composite material have been investigated to analyze its suitability for transparent flexible antenna realization. For concept demonstration, a prototype of a dual-band antenna operating at 2.33-2.53 GHz and 4.7-5.6 GHz has been fabricated and tested. These frequencies cover both the instrument, scientific, and measurement (ISM) and the wireless local area network (WLAN) bands. Full ground plane is utilized in the antenna design for on-body operations. The suitability of the antenna for wearable applications has been investigated by measuring its performance under physical deformation and testing its performance on phantom. Next, the RF performance of the antenna has been improved by using two layers of conductor to form the radiating element. Although transparency is slightly compromised, the double-layer element improves the gain and efficiency of the antenna

A Low Profile, UWB Circular Patch Antenna with Monopole-Like Radiation Characteristics

a simple ultra-wideband antenna with monopolelike radiation pattern is presented in this paper. The structure of this low profile antenna with height of the 7 mm (0.65 ;min) is based on annular-ring circular patch. To improve the antenna's bandwidth, the main annular-ring circular patch is loaded with two concentric rings and two rectangular slots. The result shows the antenna achieves a 10 dB return loss bandwidth from 2.85 GHz to 8.6 GHz. The monopole-like radiation pattern is maintained throughout the frequency bands by combining four propagation modes of TM01, TM02, and TM03

Flexible and Transparent Circularly Polarized Patch Antenna for Reliable Unobtrusive Wearable Wireless Communications.

This paper presents a circularly polarized flexible and transparent circular patch antenna suitable for body-worn wireless-communications. Circular polarization is highly beneficial in wearable wireless communications, where antennas, as a key component of the RF front-end, operate in dynamic environments, such as the human body. The demonstrated antenna is realized with highly flexible, robust and transparent conductive-fabric-polymer composite. The performance of the explored flexible-transparent antenna is also compared with its non-transparent counterpart manufactured with non-transparent conductive fabric. This comparison further demonstrates the suitability of the proposed materials for the target unobtrusive wearable applications. Detailed numerical and experimental investigations are explored in this paper to verify the proposed design. Moreover, the compatibility of the antenna in wearable applications is evaluated by testing the performance on a forearm phantom and calculating the specific absorption rate (SAR)

Polydimethylsiloxane-Embedded Conductive Fabric: Characterization and Application for Realization of Robust Passive and Active Flexible Wearable Antennas

© 2013 IEEE. We present our study on polydimethylsiloxane (PDMS)-embedded conductive fabric, which we propose as a simple yet effective solution to the challenging issue of poor PDMS-metal adhesion, allowing for a relatively easy realization of robust flexible antennas for wearable applications. The method combines the use of conductive fabric as a radiator with PDMS, which acts as the substrate and a protective encapsulation simultaneously. For the first time, a holistic study on the mechanical and electrical properties of the proposed combination of materials is presented thoroughly using a number of fabricated samples. As concept demonstrations, a microstrip patch and a reconfigurable patch antenna are fabricated using the proposed technique to validate the idea. The inclusion of a PDMS-ceramic composite as part of the antenna's substrate, which leads to over 50% reduction in the size compared with a pure PDMS, is also demonstrated to showcase further the versatility of the proposed technique. The fabricated antennas are tested in several wearable scenarios and consistent performance including reconfigurability is obtained even after the antennas are exposed to harsh environments, i.e., extreme bending and machine-washing

Flexible Transparent Antennas: Advancements, Challenges, and Prospects

Optically transparent electronic devices have attracted enormous interests in recent years. The development of transparent electronics emerges a lot of new industrial applications in variety of fields, such as displays, glasses, solar panels, satellite communications, terrestrial communications, integrated circuits, and sensors where optical transparency is required for unobtrusive placement of electronic devices on the surface. Over the last couple of years, there have been notable advancements in the development of transparent wireless electronics due to the emerge of new materials and fabrication technologies. Among transparent electronic devices, transparent antennas attract tremendous interests due to their widespread applications in healthcare industry, security sector, defence, sports, smart city, Internet of Things (IoTs) and many more. Many of these applications require antennas that are concurrently transparent and flexible. A transparent and flexible antenna can be easily integrated with displays, windows, solar cells and optoelectronic modules, thus, reducing the space in the integrated circuits. However, still the development of flexible-transparent electronics is associated with some challenges which continue to impede the progress of this emerging field. Among them are the contradictory relationship between the electrical conductivity and optical transparency of the transparent conductors, costly and complex processing of the transparent materials and unavailability of the appropriate materials. In this paper, we discuss current advancements in the development of flexible transparent antennas, including potential applications, various enabling materials and manufacturing approaches, technical hurdles, as well as prospects

Recent developments and state of the art in flexible and conformal reconfigurable antennas

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. 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

Advancements, Challenges, and Prospects of Water-Filled Antennas

In the group of liquid antennas, water antennas have attracted tremendous popularity due to the excellent electrical and mechanical properties of water. Pure water is a high permittivity dielectric liquid which comprises high dielectric constant and very low electrical conductivity. While the electrical conductivity of pure water is very low, salt-water has good electrical conductivity. The electrical conductivity of salt-water can be controlled by adjusting the ratio of salt content (salinity) in the water solution. Both pure water and salt water has excellent optical transparency, liquidity, flexibility and easy availability, thus, become excellent candidates in antenna manufacturing. Pure water is utilized as the dielectric component of the antenna and generally used in the development of dielectric resonator antennas, whereas salt-water is used as the conductive part of the antenna replacing metallic conductors. Some antennas have also utilized both the pure water and salt water for improved performance. In the literature, different classes of antennas can be found that have been developed by utilizing water. In this review paper, we have highlighted the state-of-the-art designs of water-filled antennas, highlighted the major challenges towards the development of water-filled antennas and presented the novel applications and prospects of water-filled antennas

Tunable terahertz filter/antenna-sensor using graphene-based metamaterials

In this paper, a novel tunable graphene-based bandstop filter/antenna-sensor is presented. This structure is an integrated module that can be used to combine filtering and high-gain radiation performance. The initial design of the unit cell consists of four U-shaped stubs loaded, resembling the arms of a ring and a sensing layer in the substrate. The reflection and transmission spectra are obtained for various graphene's chemical potentials and refractive index of sensing layer (Ns) of structure in the range of 1.3–1.6 THz. The proposed structure exhibits the attributes of both dual-band filter and single-band antenna-sensor. The conductivity of graphene and its structural parameters are studied to optimize the component performance. In filtering mode, the first bandstop is from 1.23 to 1.6 THz equal to 26% of fractional bandwidth (FBW) at 1.415 THz. The second stopband is centered at 3.12 THz with FBW of 14% for Ns = 1.6 and 0.6 eV chemical potential. In the antenna mode, a single band of the antenna-sensor is centered at 1.95 THz for the same Ns and same chemical potential. It is shown that a sensitivity of 0.145 THz/RIU is achieved at Ns = 1.5 and chemical potential of 0.6 eV. Additionally, the performance of the proposed filter/antenna-sensor module is investigated for different wave polarizations and oblique angles

Design and Analysis of GO Coated High Sensitive Tunable SPR Sensor for OATR Spectroscopic Biosensing Applications

In this paper, we numerically debrief an ultra-high sensitive surface plasmon resonance (SPR) biosensor utilizing thin layers of graphene oxide (GO) that have not been addressed adequately till now. By the deposition of GO on top of the metal-dielectric heterostructure, our proposed sensor can achieve higher sensitivity and higher Quality Factor (QF) simultaneously which has not been possible by the existing models to our knowledge. Because of its large surface area and sp2 inside of an sp3 matrix which is capable of confining π electrons, GO can form strong covalent bonds with biomolecules and hence enhanced light-material interaction that made researchers contemplate to achieve increased sensitivity and figure of merit. Both the transfer matrix method and finite element method are exploited to perform extensive numerical analysis for optimizing the structure considering its sensitivity, full width half maximum (FWHM), and QF. This paper examines six different configurations of multilayer heterostructure containing prism-adhesive-metal-BaTiO3/BP-Gr/GO/MXene-sensing medium, and a noticeably enhanced performance is achieved using GO with a maximum sensitivity of 372 deg/RIU and QF of 88.11 RIU-1 in the range of refractive index (RI) 1.330 to 1.353. Moreover, the possibility of designing a tunable SPR sensor to operate at a broader range of analyte's RI is investigated, and 414 deg/RIU with 119.27 RIU-1 QF at 1.407 RI is achieved. The Electric field distribution, effects of different layers, and fabrication feasibility of the proposed sensor are explored, it is envisaged that this can be an appropriate apparatus for highly sensitive, rapid, and noninvasive label-free biosensing useful in experimental sensing protocols