John C. Batchelor

A passive UHF RFID tag is proposed to monitor the growth of skin organoid cultures. The tag consists of three main components: a dipole antenna, a Magnus S2 transponder, and a sensing structure that electromagnetically couples energy to a split-ring resonator (SRR) embedded within a skin culture inside a Petri dish. The tag is optimized through simulations to achieve sufficient sensitivity while maintaining acceptable transmission performance. A skin phantom composed of 1 mm thick ham layers was used to emulate the progressive growth of the dermal tissue. The dielectric properties of the phantom are experimentally measured and confirmed to be suitable for mimicking human skin. Practical measurements are carried out using a fabricated tag and a Voyantic Tagformance Pro reader. The measured sensor code detects tissue growth up to 3 mm with a resolution of 0.5 mm. The tag also exhibits a consistent read range of approximately 8 m at 868 MHz, confirming reliable wireless communication and stable sensing performance throughout the measurements. The RFID tag system offers applications for non-invasive monitoring of tissue development in organoid cultures.

Medical implants are routinely colonized by microbial biofilms especially yeast biofilms such as those formed by Candida albicans . As medical implants move towards smart technology and IoT, it is more important than ever to understand the electrical properties of biofilm formation. Here we present an attempt at understanding how C. albicans biofilm formation effects sensor technology. We propose that as the biofilm matures, it becomes increasingly hydrophobic and undergoes a reduction in effective dielectric constant and ionic conductivity. This results in an impedance mismatch that disrupts capacitive coupling between the sensor and surrounding media, this effect that can be reliably detected. We show that a C. albicans biofilm changes its dielectric properties during maturation and, once mature, can be equated to a thin dielectric insulator. We demonstrate that these properties can be used to enable constant monitoring of a C. albicans biofilm using passive RFID, offering a new detection methodology that may be applied to surfaces known to be readily colonise.

This paper introduces a novel close-coupling guided lens technique for gravity-triggered pattern-reconfigurable antennas for aerial vehicles and communication systems. The proposed technique utilizes purposefully designed curved containers where a lens can freely slide with gravity, serving as a versatile add-on for existing aerial devices. In a basic configuration with a cylindrical container and a centered half-wavelength dipole antenna, directivity increases by 3.1 dB, enabling 360$^{\circ }$ beam steering. In a more application-based set up using dielectric resonator antennas (DRAs) with semi-cylindrical/ semi-spherical lenses 1D/ 2D beam steering is achieved, effectively covering half-space areas. A continuous beam steering of $\pm 35^{\circ }$ is demonstrated for these applications. Both solid and liquid lenses have been employed flexibly, offering a broader range of options in practical applications, and extending the viability of the proposed concept. Furthermore, only a small volume of material ($< $ 7 cm³) is needed for the lens. A good agreement between the simulated and measured results for both liquid and solid lenses has been observed, proving the feasibility of the idea. This study provides a potential low cost, energy efficient, light weight solution for inclined static platforms such as aerial vehicles, communication balloons, or simply in vehicular scenarios involving anticipated tilts or rotations.

Printed electronics using flexible substrates are an emerging area, allowing next-generation electronics to conform and flex with different surfaces, from human skin to clothing. In the hybrid integration, or sea-of-rigids, approach, conventional microchips are mounted onto (generally) plastic substrates such as polyethylene naphthalate (PEN), with (typically) printed silver tracks for interconnections between components. An ongoing research direction is to replace plastic substrates with biodegradable substrates and to replace silver tracks with non-heavy metal-based tracks. While the substrates and tracks form only part of an overall system, replacing them is a step towards increased sustainability and helps to meet net-zero goals for printed electronic systems. Previously, several papers have investigated printed carbon tracks for low-frequency analog sensing applications. This paper explores the feasibility of using printed carbon tracks on biodegradable substrates for high-frequency applications such as digital signaling over a Serial-Peripheral Interface (SPI). We investigate the printability, thermal stability, and electrical conductivity of carbon ink screen-printed onto six commercially available sustainable and flexible substrates. Our results demonstrate that multi-layer screen printing substantially reduced the electrical resistance of carbon tracks, enabling SPI communication at frequencies up to 16 MHz with three layers of carbon ink. A Natureflex™ substrate provided the best balance of printability, thermal stability, and electrical performance. Substrates such as greaseproof paper and ClearFilm PU showed potential for flexible electronics, but require further optimization. This study provides valuable insights into selecting and optimizing biodegradable substrates for high-frequency digital systems, supporting the move towards more sustainable printed electronics.

The dissemination of sensors is key to realizing a sustainable, ‘intelligent’ world, where everyday objects and environments are equipped with sensing capabilities to advance the sustainability and quality of our lives—e.g. via smart homes, smart cities, smart healthcare, smart logistics, Industry 4.0, and precision agriculture. The realization of the full potential of these applications critically depends on the availability of easy-to-make, low-cost sensor technologies. Sensors based on printable electronic materials offer the ideal platform: they can be fabricated through simple methods (e.g. printing and coating) and are compatible with high-throughput roll-to-roll processing. Moreover, printable electronic materials often allow the fabrication of sensors on flexible/stretchable/biodegradable substrates, thereby enabling the deployment of sensors in unconventional settings. Fulfilling the promise of printable electronic materials for sensing will require materials and device innovations to enhance their ability to transduce external stimuli—light, ionizing radiation, pressure, strain, force, temperature, gas, vapours, humidity, and other chemical and biological analytes. This Roadmap brings together the viewpoints of experts in various printable sensing materials—and devices thereof—to provide insights into the status and outlook of the field. Alongside recent materials and device innovations, the roadmap discusses the key outstanding challenges pertaining to each printable sensing technology. Finally, the Roadmap points to promising directions to overcome these challenges and thus enable ubiquitous sensing for a sustainable, ‘intelligent’ world.

This paper presents a minimally invasive battery-less microcontroller enabled implant that utilizes near-field communication technology to both power and transfer data to and from the implanted device. The implant has been designed around a cylindrical glass vial for its housing, of the type found in pet and livestock identification. Requiring just an injector assembly for implantation it can be deemed as minimally invasive. The prototype tag incorporates a near-field communication front end, providing data transfer and power to a microcontroller and a light emitting diode array, with a maximum measured read range of ~ 5 mm off the skin surface. Although light technology can be used for neural stimulation here it is used as a proof of concept before enabling further sensing modalities. The tag is proposed for use as a wireless platform for patient health monitoring in both clinical and home environments using a smartphone as the reader. It could also have applications in general wellbeing monitoring or sports.

This paper describes the development of a Direct Driven Resonant Radiator (DDRR) antenna for an ultra-low power UHF RFID tag system, integrating an accelerometer for movement tracking using a passive backscattering communications link. An outline of a system intended for healthcare applications involving wireless movement detection, such as therapeutic recovery exercises is described. The tag comprises of a UHF RFID transponder connected to a 4 cm (0.115λ) diameter, 1 mm thick (0.0028λ) skin-mounted antenna. Offbody read ranges of 3.6 m with 1 kB/s data communication are achieved. The DDRR radiation pattern is a limiting factor in movement tracking, offering only limited angles of detection, which could be improved with spatial diversity in the reader antennas.

Growing interest in Internet of Things (IoT) and health care pushes the exploration of innovative solutions for connecting our bodies to external systems. The need for devices interoperability combined with data rate considerations, and low-power consumption make 5G backscattering-based communications a promising opportunity, especially in the low sub-6 GHz band. Starting from a monolithic array, this communication proposes a skin-mountable miniaturized antenna suitable for 3.6 GHz body-centric backscattering communications. The array is an improved version of the comb-line antenna, which simultaneously optimizes size and radiation features. The horizontal segments are folded such to place the radiating dipoles closer and increase the radiation efficiency of the structure by co-phasing a single component of the surface currents. Parametric analysis obtains optimal configurations in terms of gain and size. Compared to conventional layout, the miniaturized array has an efficiency 6 dB higher and an area 80% smaller while the improved structure provides a theoretical read distance of more than 4 m. Measurements on a volunteer corroborate the improved performance.

Capacitive loading due to human tissue can lead to low efficiency for implantable Passive Radio Frequency Identification (RFID) antennas. The presented passive UHF antenna sensor provides read distances above 0.5 meters (within a body phantom) by utilizing a convoluted half-wave dipole design. It is able to detect simulated early to mature Candida albicans biofilm growth when mounted upon a voice prosthesis (up to a 30 μm biofilm thickness). Depending on the propagation frequency of interest, as early 4-hour growth (5 to 10 μm biofilm thickness) equivalent could be detected and before any device failure could occur due to the colonization. This was accomplished by utilising thin layers of polyurethane to decouple the saliva from the presented UHF sensor (biofilm growth is known to increase layer hydrophobicity). This presented sensor has better functionality within the U.S. UHF frequency band as it detects changes above 5 μm. If there is a need for implantation within additional tissues with variable dielectric properties, a shunt capacitance of 2.6 pF could allow the system functionality within the permittivity range of 21 to 58. Allowing for immediate medical intervention before medical prosthesis failure.