Mohamed A. Ziai

Temporary On-Skin Passive UHF RFID Transfer Tag

A passive UHF RFID tag design is presented in the form of a transfer patch similar to a temporary tattoo that is mountable directly onto the skin surface. The transfer tag is suitable for monitoring of people over time in mission critical and secure environments. The antenna reactance is first calculated to conjugate match the measured RFID chip reactance and then full wave simulation is used to design the tag with good performance on a human flesh model. Finally the tag read range is measured on different parts of a volunteers body and compared to simulated read range values for the entire RFID bands.

Towards inkjet-printed low cost passive UHF RFID skin mounted tattoo paper tags based on silver nanoparticle inks

The present work describes the inkjet printing and low temperature sintering of silver nanoparticle inks onto transfer tattoo paper. Our approach results in silver features of excellent resolution and conductivity and, subsequently the first passive UHF RFID transfer tattoo tags functional mounted on human skin of improved performance when compared to screen printed passive UHF RFID transfer tattoo paper tags. Moreover, inkjet printed passive UHF RFID transfer tattoo tags show similar performance to copper etched passive UHF RFID tags on plastic substrates. This study compares the image quality (resolution) and electrical performance of two commercial silver nanoparticle inks inkjet printed on transfer tattoo paper. The optimal printing and sintering parameters to obtain high resolution features of resistivities 20 to 57 times the resistivity of bulk silver (1.59 × 10−6 ohm cm) are described. We demonstrate how, by selectively depositing ink in specific areas of the antenna, read distance of passive UHF RFID tags can be increased from 54 to 68 cm whilst decreasing the amount of ink used by 33%. Furthermore, this approach results in inkjet printed passive UHF RFID tattoo tags with larger read distance than silver screen printed passive UHF RFID tattoo tags, 45 cm, and similar to copper etched passive UHF RFID plastic tags, 75 cm. Moreover, inkjet printed passive UHF RFID tattoo tags in this work are considerably thinner (1–5 μm) than screen and etched passive UHF RFID tags (tens of micrometers) hence, making the former more appealing to the end user. In addition to this, inkjet printing is compatible with large area manufacturing techniques and has the potential to evolve as one of the most promising RFID mass-production techniques. Therefore, this work represents a step towards the commercialization of on-body transfer tattoo paper passive UHF RFID tags.

Swelling of PDMS networks in solvent vapours; applications for passive RFID wireless sensors

The relative degree of swelling of a poly(dimethylsiloxane) (PDMS) network in organic vapours is demonstrated to be related to the chemical and physical properties of the organic compounds. The swelling ratio, based on volume change, QV, is directly correlated with the Hansen solubility parameters, δd, δp and δh and the vapour pressures of the organic vapours employed. A practical use for such PDMS networks in combination with an understanding of the relationship is demonstrated by the use of PDMS as a mechanical actuator in a prototype wireless RFID passive sensor. The swelling of the PDMS displaces a feed loop resulting in an increase in transmitted power, at a fixed distance.

UHF RFID tag antenna design for on-body applications

This paper addresses the antennas design for passive UHF rfid applications involving the human body as the object to be tagged. Novel antenna geometry is proposed for conjugate impedance matching to the complex impedance of the rfid transponder. The proposed tag is capable of achieving high read range directly attached to a human thorax or in free space.

Switchable disposable passive RFID vapour sensors from inkjet printed electronic components integrated with PDMS as a stimulus responsive material

A route to cheap and disposable sensors for the chemical sensing market, with potential applications including monitoring of food spoilage, is reported herein. The sensor is the result of the direct integration of a stimuli-responsive material, poly(dimethylsiloxane) (PDMS), with an electronic component. The printing and sintering of colloidal silver ink solutions onto PDMS was optimized to allow the printing of conductive silver feed loops, which are the active sensing component in antennas for passive (battery-free) Radio Frequency Identification (RFID) tags. The response of these devices is related to the degree of swelling of the PDMS, which, in turn, has been shown to be correlated to the Hansen solubility parameters and the vapour pressures of the corresponding volatile organic compounds (VOCs). When exposed to solvent vapour the printed feed loop fractures, increasing resistance and ultimately breaking conductivity, leading to a change in the transmitted power and read range of the wireless device. Remarkably upon removal from the vapour, the fractured feed loops reassemble and become conductive again, making them switchable and “multi-use”. This work paves the way to a fully inkjet printed RFID substrate for vapour detection.

RCS and read range of a UHF RFID tag

The development of a novel RFID tag operating at 869 MHz and its performance evaluation using simulated Radar Cross Section (RCS) are presented. The RCS variations of the tag antenna are evaluated over azimuth and elevation angular ranges for three cases of load: short, matched load and open. The tag exhibits appreciably good differential RCS between its switching states over wide azimuth angular ranges and over the entire elevation angular ranges. The measured read range variations over the azimuth and elevation angular ranges are also presented to validate the simulated results.

Smart radio-frequency identification tag for diaper moisture detection

A passive smart tag is described that responds to dampness in diapers once a pre-defined threshold value is reached. A high-frequency (HF) system at 13.56 MHz is used as this allows operation through water or human tissues with less absorption that would occur for an ultra-HF signal. A circular spiral coil and swelling substrate facilitate a reaction to dampness that can be detected without contact to the diaper wearer. A prototype design is simulated and measured results are provided together with a demonstration of a tag integrated into a worn diaper.

Developing inkjet printing to enable low cost UHF RFID transfer tattoo tags

This paper demonstrates the use of inkjet printing as a digital fabrication tool for the cost effective manufacture of radio frequency identification (RFID tags on low-cost flexible and porous substrates. The design presented in this work is a thin, substrate tolerant UHF RFID tag that can be mounted directly onto the skin surface in the form of a transfer patch in the same way that a temporary tattoo is applied.

RFID TAGs as transfer tattoos

A range of designs are presented illustrating how RFID tags can be realized as temporary transfer tattoos for use in applications such as medical and security systems. The prototype tags work at the RFID UHF band (867MHz) and have read ranges from about 50cm to 2.75m.

Effect of skin dielectric properties on the read range of epidermal ultra-high frequency radio-frequency identification tags

This Letter presents an investigation of the effect of human tissue conductivity and permittivity on the performance of epidermal transfer tattoo ultra-high frequency radio-frequency identification (RFID) tags. The measurements were carried out on 20 individuals and the variations in the measured dielectric properties correlate well with variations in the measured tag read range on the individuals and to a lesser extent with their body mass index values. Simulation results also showed the effects of permittivity and conductivity on the designed resonance frequency of the RFID tag.