Search

Traditionally, radio frequency detection or ambient spectrum sensing has required high-performance spectrum analyzers and RF signal analyzers, leading to relatively high costs due to the need for a local oscillator and signal mixer. To overcome this challenge, we propose a low-cost, substantially simplified solution utilizing a stretchable rectenna, a microcontroller unit (MCU), and feedback control systems. By exploiting the dynamic correlation between the resonant frequency and the tensile ratio of the stretchable antenna, the incoming frequency can be determined by recording the maximum rectifier DC power output as a function of the electromechanically controlled tension ratio of the stretchable antenna. Our measured results indicate that a frequency measurement range of 1.8 GHz to 2.5 GHz can be achieved through careful design of the stretchable antenna and broadband rectifier. We have experimentally demonstrated an over-the-air far-field frequency sensing system based on this concept, showcasing significant advantages in power consumption, cost-effectiveness, and simplicity when compared to state-of-the-art RF spectrum analyzers.

The manuscript presents a novel approach to designing and fabricating a stretchable patch antenna designed for strain sensing and the wireless communication of sensing data at the same time. The challenge lies in combining flexible and stretchable textile materials with different physical morphologies, which can hinder the adhesion among multiple layers when stacked up, resisting the overall stretchability of the antenna. The proposed antenna design overcomes this challenge by incorporating a lattice hinge pattern into the non-stretchable conductive e-textile, transforming it into a stretchable structure. The innovative design includes longitudinal cuts inserted in both the patch and the ground plane of the antenna, allowing it to stretch along in the perpendicular direction. Implementing the lattice hinge pattern over the conductive layers of the proposed patch antenna, in combination with a 2 mm thick Polydimethylsiloxane (PDMS) substrate, achieves a maximum of 25% stretchability compared to its counterpart antenna without a lattice hinge design. The stretchable textile antenna resonates around a frequency of 2.45 GHz and exhibits a linear resonant frequency shift when strained up to 25%. This characteristic makes it suitable for use as a strain sensor. Additionally, the lattice hinge design enhances the conformability and flexibility of the antenna compared to that of a solid patch antenna. The realized antenna gains in the E and H-plane are measured as 2.21 dBi and 2.34 dBi, respectively. Overall, the presented design offers a simple and effective solution for fabricating a stretchable textile patch antenna for normal use or as a sensing element, opening up possibilities for applications in the communication and sensing fields. [ABSTRACT FROM AUTHOR]

The manuscript presents a novel approach to designing and fabricating a stretchable patch antenna designed for strain sensing and the wireless communication of sensing data at the same time. The challenge lies in combining flexible and stretchable textile materials with different physical morphologies, which can hinder the adhesion among multiple layers when stacked up, resisting the overall stretchability of the antenna. The proposed antenna design overcomes this challenge by incorporating a lattice hinge pattern into the non-stretchable conductive e-textile, transforming it into a stretchable structure. The innovative design includes longitudinal cuts inserted in both the patch and the ground plane of the antenna, allowing it to stretch along in the perpendicular direction. Implementing the lattice hinge pattern over the conductive layers of the proposed patch antenna, in combination with a 2 mm thick Polydimethylsiloxane (PDMS) substrate, achieves a maximum of 25% stretchability compared to its counterpart antenna without a lattice hinge design. The stretchable textile antenna resonates around a frequency of 2.45 GHz and exhibits a linear resonant frequency shift when strained up to 25%. This characteristic makes it suitable for use as a strain sensor. Additionally, the lattice hinge design enhances the conformability and flexibility of the antenna compared to that of a solid patch antenna. The realized antenna gains in the E and H-plane are measured as 2.21 dBi and 2.34 dBi, respectively. Overall, the presented design offers a simple and effective solution for fabricating a stretchable textile patch antenna for normal use or as a sensing element, opening up possibilities for applications in the communication and sensing fields.

Herein, a wireless and soft smart contact lens that enables real‐time quantitative recording of cholesterol in tear fluids for the monitoring of patients with hyperlipidemia using a smartphone is reported. This contact lens incorporates an electrochemical biosensor for the continuous detection of cholesterol concentrations, stretchable antenna, and integrated circuits for wireless communication, which makes a smartphone the only device required to operate this lens remotely without obstructing the wearer's vision. The hyperlipidemia rabbit model is utilized to confirm the correlation between cholesterol levels in tear fluid and blood and to confirm the feasibility of this smart contact lens for diagnostic application of cholesterol‐related diseases. Further in vivo tests with human subjects demonstrated its good biocompatibility, wearability, and reliability as a non‐invasive healthcare device. [ABSTRACT FROM AUTHOR]

Abstract Herein, a wireless and soft smart contact lens that enables real‐time quantitative recording of cholesterol in tear fluids for the monitoring of patients with hyperlipidemia using a smartphone is reported. This contact lens incorporates an electrochemical biosensor for the continuous detection of cholesterol concentrations, stretchable antenna, and integrated circuits for wireless communication, which makes a smartphone the only device required to operate this lens remotely without obstructing the wearer's vision. The hyperlipidemia rabbit model is utilized to confirm the correlation between cholesterol levels in tear fluid and blood and to confirm the feasibility of this smart contact lens for diagnostic application of cholesterol‐related diseases. Further in vivo tests with human subjects demonstrated its good biocompatibility, wearability, and reliability as a non‐invasive healthcare device.

Sensor-laden wearable systems that are capable of providing continuous measurement of key physiological parameters coupled with data storage, drug delivery and feedback therapy have attracted huge interest. Here we report a stretchable wireless system for sweat pH monitoring, which is able to withstand up to 53% uniaxial strain and more than 500 cycles to 30% strain. The stretchability of the pH sensor patch is provided by a pair of serpentine-shaped stretchable interconnects. The pH sensing electrode is made of graphite-polyurethane composite, which is suitable for biosensor application. The sensing patch validated through in-depth electrochemical studies, exhibits a pH sensitivity of 11.13 ± 5.8 mV/pH with a maximum response time of 8 s. Interference study of ions and analyte (Na + , K + and glucose) in test solutions shows negligible influence on the pH sensor performance. The pH data can be wirelessly and continuously transmitted to smartphone through a stretchable radio-frequency-identification antenna, of which the radiating performance is stable under 20% strain, as proved by vector network analyzer measurement. To evaluate the full system, the pH value of a human sweat equivalent solution has been measured and wirelessly transmitted to a custom-developed smart phone App. [ABSTRACT FROM AUTHOR]

This article describes the implementation of a wireless human motion detection with interference resistance to untargeted deformations based on a stretchable patch antenna with fractal design. By rationally incorporating the Hilbert fractal pattern in the conductive patch and ground plane, the patch antenna shows a mechanical stretchability of ∼40% and a maximum gain of 2.95 dB at 2.5 GHz. Furthermore, the influence of the fractal order on the mechanical stretchability and radiation properties of the stretchable patch antenna is discussed. The resonant frequency of the stretchable fractal antenna demonstrates highly selective sensitivity to different deformations; i.e., it remains almost unchanged with bending deformations and is linearly dependent on the tensile strain. Remote detection of joint motions is experimentally verified by a wireless on-body strain sensor based on the fractal design-based stretchable microstrip antenna.

A simple soluble salt-driven matrix swelling method was developed for fast fabrication of a silver nanoparticle-based conductive elastomer. Taking advantage of the synergistic effects of silver trifluoroacetate and methanol, the swelling capability of an elastomeric block copolymer polystyrene- block -polyisoprene- block -polystyrene (SIS) was greatly enhanced. The interaction of silver ions and double bonds of the copolymer enables fast infiltration of soluble salt into the polymer network, resulting in a high-content loading of silver ions, which is a prerequisite for fabrication of a highly conductive polymer. In-situ reduction was performed under a swollen state to allow the reducer to effectively penetrate into the polymer matrix, thoroughly reducing the silver salt into silver nanoparticles. A three-layered conductive elastomer was obtained, with a high concentration of silver nanoparticles formed on both surfaces of SIS copolymer. Typically, the conductivity of the reduced SIS elastomer was measured to be > 2 × 10 5 S/m when ε = 0, and can maintain to be over one seventh of its initial value even at a 200% elongation. The conductive elastomer can withstand over 1000 stretch-release cycles under a strain of 100%. A radio-frequency antenna was prepared with the conductive elastomer, which gives the ability of dimension tuning, to realize high-quality frequency-selective radiation at a wide bandwidth of larger than 2.6 GHz. [ABSTRACT FROM AUTHOR]

A new process is presented to fabricate stretchable and flexible wire antennas using conductive fibers (E-fibers). Stretchability and flexibility are important for wire antennas that operate in environments subjecting them to shape deformation (e.g., automotive, wearable, implantable applications, etc.). The concept is to embroider the wire antenna using E-fibers and embed it into a stretchy polymer. This also preserves the integrity of the textile threads and protects them from corrosion. A key challenge is to remove the non-stretchable fabric on which the textile antenna was embroidered while still preserving its original shape. To validate our technology, we fabricate and test a stretchable and flexible wire antenna operating at 915 MHz. The E-fiber prototype is found to achieve excellent performance, comparable to that of its non-stretchable and non-flexible copper-wire counterpart. A future goal is to embed such antennas into hostile environments, such as a truck tire, for collecting automotive data. [ABSTRACT FROM AUTHOR]

A frequency-reconfigurable microstrip patch antenna is implemented using a stretchable silicone TC5005 substrate. The stretchable patch is fabricated by injecting liquid metal alloy Galinstan into a square reservoir fabricated in the silicone elastomer substrate. An aperture-coupled feeding method is presented to enhance the strain by separating the fixed feed element from the stretched radiating element. The implemented prototype is demonstrated to be stretchable by a strain of up to 300% (and the material has the potential for more). The electrical length of the patch antenna varies with the stretching, and we demonstrate frequency tuning from 1.3 to 3 GHz. A maximum radiation efficiency of 80% is measured for the antenna. The fabrication process of the antenna system and experimental results for impedance and radiation pattern are presented. [ABSTRACT FROM AUTHOR]

• 3-D LM composite with high electrical conductivity of 105–106 S/m is fabricated. • Soft antennas with ultimate strain of 300% are achieved based on 3-D LM composite. • The antenna presents a strain-independent reflection coefficient of around −30 dB. • The antenna exhibits stretch-tuned resonant frequency over wide frequencies. • Both softness of LM and protection from stiff layer contribute to the performance. We develop a class of stretchable dipole antennas based on embedding three-dimensional liquid metal network into an elastically soft elastomer as conductive branches, which can be highly stretched up to a strain of 300% while presenting high-quality reflection coefficient around −30 dB and a wide range of tunable resonant frequency from 1.55 to 0.45 GHz simultaneously. Neither mechanical damage nor performance degradation was observed during 100 stretch-release cycles under 100% strain for the antennas. The high electrical conductivity and deformation reversibility of the liquid metal, super stretchability of the soft elastomer and protection from the rigid layer are responsible for such a unique performance, enabling potential application for wireless strain sensors. [ABSTRACT FROM AUTHOR]