Self-healing functional polymers, composites, and blends have the potential to provide cutting-edge solutions for advancing fully soft, elastic electronics, antennas, and sensors. In this letter, we present the first prototype and performance evaluation of a slot type passive UHF RFID tag antenna made of self-healing insulative elastomer substrate and self-healing conductive laser cut PEDOT:PSS-based blend film. The measured maximum read range of the self-healing tag varied from 1.7 to 1.8 meters within the frequency range of 860-960 MHz, which covers the UHF RFID bands used worldwide. Taking into account the current conductivity of the self-healing polymer (150 S/m), this is a promising result and demonstrates, for the first time, a completely self-healing polymer-based UHF RFID tag antenna. In addition, we have demonstrated direct attachment of the RFID IC strap to the radiator without any additional adhesives. Moreover, the good agreement between the simulated and measured data confirms the applicability of the antenna modelling approach to the fully self-healing elastomer-based antenna. The work presented in this paper provides proof-of-concept in development of self-healing antennas, sensors and electronics. One of the most important aspects for future work is increasing the conductivity of the self-healing polymer.

We present the development and optimization of a quad-band meandered implantable Planar Inverted-F Antenna (PIFA) for wireless brain health monitoring. The design of an implantable antenna is of prime importance in implantable wireless biomedical telemetry systems for establishing wireless data connection. Through numerical optimization based on the full-wave EM simulations, we have achieved operation on four central wireless communication bands for healthcare systems: Medical Device Radiocommunication Service (MedRadio) band (401–406 MHz), Wireless Medical Telemetry Service (WMTS) band (1427–1432 MHz), and Industrial, Scientific, and Medical (ISM) bands (902.8–928 MHz, 2400–2483.5 MHz), with reflection coefficient below −10 dB. The meandered miniaturizing technique is deployed to compact the size of the antenna. A shorting pin is introduced for shorting the radiating part to the ground plane, the biocompatible silicone coating is used to prevent the direct contact of the antenna with the body, and the high-permittivity substrate Rogers RO3210 is used. For the full-wave electromagnetic field simulation, the 7-layer human head model is utilized, and the antenna is implanted at the depth of 13.25 mm of the cranial cavity in the cerebrospinal fluid (CSF) layer. The antenna volume is 11 × 19.8 × 1.8 mm 3 including the silicone coating.

Self-healing functional polymers, blends, and composites provide a compelling approach for fully soft, elastic electronics and wireless sensing technologies. In this paper, we present a numerical analysis of an RFID tag antenna employing a self-healing substrate and conductor with conductivity of similar to 150 S/m. Despite the lower conductivity comparison with the metallic conductors (similar to 60 MS/m), the flexible tag antenna achieves sufficient radiation performance in the UHF band ranging from 868 MHz to 920 MHz for a functioning RFID tag readable at 2.4 meters distance from the reader. To our knowledge, this is the first self-healing UHF RFID tag for versatile applications including healthcare, wireless communication systems, biomedicine, logistics, and different fields in the manufacturing industry.

We compare the radiation performance and the specific absorption rate (SAR) of two brain-implantable PIFAs operating in the Medical Device Radiocommunication Service (MedRadio) band (401-406 MHz), Wireless Medical Telemetry Service (WMTS) band (1427-1432), and Industrial, Scientific and Medical (ISM) bands (902-928 MHz and 2400-2483.5 MHz). The two antennas have the same total thickness and occupy the same volume, but one is based on a single substrate layer and the other also includes superstrate. A feature shared by the two antennas was that the maximum SAR occurred at the interface between the biocompatible encapsulation layer and the surrounding tissues, whereas neither antenna performed superior to the other in terms of SAR or the radiation performance considering all four operating frequencies.

The electrochemical analysis is one of the most popular implementations of a dopamine-sensing brain implant. Its performance depends significantly on the interaction between the dopamine molecule and the working electrode. Carbon nanofiber is an allotrope of carbon nanotube and is effective in increasing the contact surface with dopamine molecules. Considering its simple fabrication protocols using photolithography, physical vapor deposition, and electrochemical deposition, this material is suitable for in-vivo implementation. COMSOL simulation confirms that carbon nanofiber implementation increases the redox current while maintaining its linearity to the user-controlled dopamine concentration.

The role of front-end electrode sensors for dopamine-detection brain implants is significant for the entire measurement process. The electrode material determines the sensitivity, selectivity, and longevity of the implant. Carbon-based electrode induces better dopamine adsorption due to π-interaction. We tested carbon fiber microelectrode (CFME) on a set of dopamine solution concentrations (1 mM to 0.01 mM) to determine its limit of detection and its reliability for quantitative analysis. The raw signal is processed using ∆Σ-converter and the concentration is estimated using a linear regression technique. The wireless feature is incorporated with a triple-band antenna at frequencies of 402, 902, and 2450 MHz for data communications, wireless power transmission, and switching control.

This research work is aimed at studying different rock types and the effect of their mineral contents on an active 434 MHz RFID card’s radio signal attenuation. This research was done at the ONKALO nuclear waste storage facility using radio frequency identification (RFID) equipment. First, the studied area and research plan, including the used system and equipment, are explained. After this, the researched areas of rock types and their effects on radio signals are presented. This work focused mainly on occupational safety, but it also investigated whether it would be possible to use RFID technology in producing mines as well, especially in the boundary layer of the ore body. This research can help the design of communication frequencies for autonomous devices.

In Parkinson's disease (PD), dopamine neurons degenerate in the Substantia Nigra, and there is a reduction of dopamine in the caudate-putamen. The diagnosis of PD is principally clinical, although specific investigations (such as PET scans) can help the differential diagnosis from other forms of parkinsonism. A brain implant that enables continuous dopamine monitoring would be helpful for Parkinson's disease patients. We address an RFID-based solution for data transmission and power transfer that facilitate the implementation of a fully implantable and batteryless brain implant. The wireless operation takes place on three frequency bands of 402, 902, and 2400 MHz for data telemetry, power transfer, and switching control, respectively.

In this paper and presentation, we will focus on different aspects of backscattering-based wireless communication and power transfer to small biomedical implants. We will present three different antenna topologies for data and power transfer through tissue, in vitro and in vivo studies on implantable intracranial pressure (ICP) sensors and give insight and analysis on wireless link reliability in tissue environment. We will also present radio frequency identification (RFID) -based implant platform and communication method. Moreover, we will focus on differences and challenges of in vivo environment compared to laboratory phantoms and tissue models. In our studies, different types of implantable antennas have been tested to investigate reliability, accuracy and sensitivity of the brain implants: a hybrid near field-far field system with a piezoresistive sensor for ICP monitoring, a UHF band spilt-ring resonator system and LC tank based miniature implantable antenna. This paper will present these implant antennas and wireless power transfer in tissue environment present in human head.

Motoric symptoms in Parkinson’s disease (PD) patients are caused by low level of dopamine (DA) concentration in the brain. Facilitating daily real-time and portable DA monitoring can improve the life quality of the patients. Miniaturized wireless brain implant can accommodate this purpose. The realization of this device requires compatible design on DA sensor, signal processing, and the wireless technology. For the sensor, the electrochemical method, Fast Scan Cyclic Voltammetry (FSCV), enables the sub-millisecond DA concentration measurement. Coupling this sensing method with RF technology and wireless power transfer can increase the device miniaturization and implantability. From our numerical analysis, the FSCV electrode with planar area approximately one square centimeter can accommodate the low-level DA concentration detection.

This article presents a study of the tunable impedance matching to our recently reported compact self-matched triple-band brain-implantable planar-inverted-F antenna (PIFA). It operates at Medical Device Radiocommunication Service (MedRadio) band (401–406 MHz) and Industrial, Scientific, and Medical (ISM) bands (902–928 MHz and 2400–2483.5 MHz). To achieve this, we investigated the optimal reflection coefficient characteristics of PIFA at desired frequencies by employing four $\pi$ - and T-type matching circuits. Our results show that a T-type circuit selected for further assessment provides suitable fine-tuning possibilities for all combinations of desired upwards and downwards frequency-tuning of the three operating frequencies to ensure reliable wireless implant communications.

This article presents a method of obtaining an equivalent lumped element circuit to model the electrical connector-line transitions in the ultra-high frequency (UHF) band. First, the scattering matrices of two microstrip transmission lines that are otherwise identical but have the physical lengths of dd and 2d2⁢d are measured. Next, the theoretical model of the lines cascaded with the connector-line transitions modeled as lumped element circuits is established. The selection of the line lengths to be dd and 2d2⁢d results in an over determined system of equations that links the circuit component values to the two-port network parameters of the cascaded system. Finally, the least-squares data fitting procedure yields the best-fit component values. The results show that in our tested scenario, 3-component reactive circuit models well the transitions. Compared with the previous methods, the proposed approach does not require knowledge of the dielectric properties of the substrate of the measured transmission lines. This property integrates the method with our previous work on estimating a microstrip line substrate’s relative permittivity and loss tangent. The obtained transition circuit model is also validated through the testing of two quarter-wave transformers. The lines and transformers are implemented on a textile substrate to highlight the method’s applicability to wearable textile-based electronics.

Wireless intracranial implantable microsystems are believed to potentially innovate the management of brain disorders and the treatment of neurological diseases. The fundamental challenge in the development of the wireless implantable system is the attainment of miniature antennas achieving adequately high efficiency for signaling and wireless power transfer in the presence of the dissipative intracranial tissues. Here, we demonstrate and evaluate an effective approach that utilizes the coupled split rings to develop the miniature implantable antenna. With the proposed approach, the antenna size can be decreased to π × (3 × 1.5) × 1 mm 3 which is less than 2% of the operating wavelength at 915 MHz, while the antenna maintains the gain of -25 dBi when placed 16 mm deep in the anatomical human head model. As a proof of concept, we developed RFID tags based on the proposed antenna and verified their performance with tissue mimicking liquid and in vivo experiment with rats. The measured maximum read range of the tags reaches 0.7 and 1.1 m when immersed 30 mm in the tissue mimicking liquid and implanted 6 mm in a rat's cranial cavity, respectively.

We optimize and characterize our latest reported small triple-band implantable planar inverted-F antenna (PIFA) resonating at Medical Device Radiocommunication Service (MedRadio) band (401–406 MHz), and Industrial, Scientific, and Medical (ISM) bands (902–928 MHz and 2400-2483.5 MHz) for wireless brain implants. To this end, we used a numerical 7-layer human head model to assess the impact of the substrate and superstrate properties on the peak gain of the antenna. Our results have demonstrated the gain improvements of 2 dB and up to 4.4 dB in the MedRadio and ISM bands, respectively, by optimizing the substrate properties and removing the superstrate.

In this study, a moisture-stimulated three-dimensional printing filament was printed onto an elastic band. The created textile platform changes its shape permanently after exposure to a high-moisture environment. Three main manufacturing parameters – that is, the printed pattern’s infill percentage, the printed pattern’s thickness, and the textile stretch – were tested to study their effects on the platform curving process. It was observed that an increase of the printed pattern’s infill density from 20% to 80%, or the printed pattern’s thickness from 1.3 to 1.7 mm, resulted in reduced curvature, whereas an increase in the elastic band’s stretch extent from 120% to 130% of its original length increased the curvature. The achieved results can be very useful in the design and development of future four-dimensional printed structures, as well as in optimizing and programming moisture sensor performance, as several sensor manufacturing parameters can be modified according to the application and use environment.

The major challenge in developing a wireless brain implant is to establish a stable and efficient trans-cranial wireless link with an integrated implantable antenna. This chapter discusses the challenges in developing the intracranial implantable antennas and compares different techniques for wireless power transfer in the presence of human body tissues. It provides a summary of the most recent miniature implantable antennas and inductive power transfer systems for implantable applications. Next, the chapter compares the merits of different methodologies to build the computational head models for implantable antenna development. A comparison of the human head models with different complexity is provided. Then, the chapter discusses the development and the performance of a wirelessly powered intracranial pressure sensing system integrating near- and far-field antennas in the human head environment. Two far-field radio-frequency identification antennas for intracranial wireless communication are demonstrated and evaluated. Finally, the chapter discusses the antenna performance and the tuning parameters through a parametric analysis.

We present a quasi-Yagi antenna mounted on a periodic surface for a wearable UHF RFID reader operating in the UHF RFID frequency band centered at 915 MHz. The periodic surface was co-optimized with the antenna to enhance the launching of surface waves to enable the end-fire radiation along the forearm so that a user can identify objects by pointing her/his hand towards them. In addition to the radiation pattern modification, the ground plane of the periodic surface serves the second purpose of isolating the antenna from the human body. We optimized the antenna in a full-wave EM simulator using a simplified cylindrical model of the forearm and in the simulation, it achieved the end-fire directivity of 5.9 dBi along the forearm. In the wireless testing, the quasi-Yagi antenna provided the read range of 3.8 m for a typical UHF RFID tag having 0 dBi gain when the reader's output power was 32 dBm that corresponds with EIRP =0.56 W and SAR =0.191 W/kg in our simulations. Considering both, the RFID emission regulations with EIRP = 3.28 W or 4 W and the SAR limit of 1.6 W/kg averaged over 1 gram of tissue, the read range could be further enhanced for reader units with higher output power.

We present the performance evaluation of a wearable quasi-Yagi RFID reader antenna fabricated using a 2mm thick flexible Ethylene Propylene Diene Monomer (EPDM) foam substrate, exhibiting end-fire radiation properties along the human body surface. The designed antenna operates for Wireless Body Area Networks (WBAN) and UHF RFID reader applications at 915MHz frequency. The quasi-Yagi antenna comprises the Yagi-type radiator, a periodic surface that launches a surface-wave to achieve the end-fire radiation properties, and a ground plane that provides isolation between the radiating element of the antenna and the human body. In a full-wave EM simulator, the wearable antenna achieved the end-fire directivity of 5.9dBi, when mounted on a homogenous cylindrical body model. The relative size of the quasi-Yagi antenna is $0.22 \lambda_{o} \times 0.33 \lambda_{o}$ with an overall thickness of 4mm. The cording to the theory of transformation acoustics and its performance of the wearable antenna is evaluated at various locations of the human body i.e., on the head, the shoulder, and the back, and also under different bending scenarios. The results show that the antenna is robust towards these variations and retains its impedance matching under the bending scenarios that can be expected in the application. We also measured the realized gain of the antenna using a dipole UHF RFID test tag with a gain of 0dBi at 915MHz frequency. The wearable antenna shows realized gain of -6.7 dBi for the head, - 6.9 dBi for the shoulder, and -7.6 dBi for the back of the human body. Overall, the antenna shows promising results for the wearable WBAN and UHF RFID reader applications.

We present a meandered triple-band planar-inverted-F antenna (PIFA) for integration into brain-implantable biotelemetric systems. The target applications are wireless data communication, far-field wireless power transfer, and switching control between sleep/wake-up mode at the Medical Device Radiocommunication Service (MedRadio) band (401–406 MHz) and Industrial, Scientific and Medical (ISM) bands (902–928 MHz and 2400–2483.5 MHz), respectively. By embedding meandered slots into the radiator and shorting it to the ground, we downsized the antenna to the volume of 11 × 20.5 × 1.8 mm3. We optimized the antenna using a 7-layer numerical human head model using full-wave electromagnetic field simulation. In the simulation, we placed the implant in the cerebrospinal fluid (CSF) at a depth of 13.25 mm from the body surface, which is deeper than in most works on implantable antennas. We manufactured and tested the antenna in a liquid phantom which we replicated in the simulator for further comparison. The measured gain of the antenna reached the state-of-the-art values of −43.6 dBi, −25.8 dBi, and −20.1 dBi at 402 MHz, 902 MHz, and 2400 MHz, respectively.

In the growing efforts of promoting patients’ life quality through health technology solutions, implantable wireless biomedical telemetry systems have been identified as one of the frontrunners. In these systems, the design of implantable antennas is of prime importance in establishing the wireless data link. Small multitasking implantable antennas are an evolving wireless health technology for monitoring medical conditions. These implantable antennas are intended for different functions including wireless data transmission at Medical Device Radiocommunication Service (MedRadio) band (401-406 MHz) and Wireless Medical Telemetry Service (WMTS) bands (1395-1400, and 1427-1432), wireless power transfer, and control signals between sleep/wake-up modes at Industrial, Scientific, and Medical (ISM) bands (902-928 MHz and 2400-2483.5 MHz), respectively. In this paper, we present a meandered quad-band planar inverted-F antenna (PIFA) for wireless brain care. Employing the meandering miniaturizing technique, shorting the radiator to the ground plane, and high-permittivity substrate/superstrate layers (Rogers RO3210; $\varepsilon_{r}=10.2, \tan \delta=0.003, h=0.635 mm$) lead to downsizing the antenna volume greatly to $11 \times 20.5 \times 1.8 mm^{3}$ that includes the biocompatible silicone coating. We developed and characterized the proposed antenna numerically utilizing a 7-layer human head model in full-wave electromagnetic field simulation, where the antenna was implanted in the cerebrospinal fluid (CSF) layer at the depth of 13.25 mm in the cranial cavity. Overall, we achieve a compact quad-band implantable PIFA with -42.3 dBi of gain with a radiation efficiency of 0.003 % at 402 MHz, -22.7 dBi gain with a radiation efficiency of 0.1 % at 902 MHz,-23.7 dBi gain with a radiation efficiency of 0.1 % at 1430 MHz, and -29.7 dBi gain with a radiation efficiency of 0.02 % at 2450 MHz. To our knowledge, this is the first self-matched quad-band antenna proposed for wireless implant communications.