This article focuses on the fabrication and characterization of stretchable interconnects for wearable electronics applications. Interconnects were screen-printed with a stretchable silver-polymer composite ink on 50-μm thick thermoplastic polyurethane. The initial sheet resistances of the manufactured interconnects were an average of 36.2 mΩ/◽, and half the manufactured samples withstood single strains of up to 74%. The strain proportionality of resistance is discussed, and a regression model is introduced. Cycling strain increased resistance. However, the resistances here were almost fully reversible, and this recovery was time-dependent. Normalized resistances to 10%, 15%, and 20% cyclic strains stabilized at 1.3, 1.4, and 1.7. We also tested the validity of our model for radio-frequency applications through characterization of a stretchable radio-frequency identification tag.

Abstract-This paper presents a novel inkjet-printed humidity sensor tag for passive radio-frequency identification (RFID) systems operating at ultrahigh frequencies (UHFs). During recent years, various humidity sensors have been developed by researchers around the world for HF and UHF RFID systems. However, to our best knowledge, the humidity sensor presented in this paper is one of the first passive UHF RFID humidity sensor tags fabricated using inkjet technology. This paper describes the structure and operation principle of the sensor tag as well as discusses the method of performing humidity measurements in practice. Furthermore, measurement results are presented, which include air humidity-sensitivity characterization and tag identification performance measurements.Index Terms-Inkjet, radio-frequency identification (RFIF), relative humidity (RH), sensor.

Abstract-Passive UHF RFID tag consists of a microchip attached directly to an antenna. Proper impedance match between the antenna and the chip is crucial in RFID tag design. It directly influences RFID system performance characteristics such as the range of a tag. It is known that an RFID microchip is a nonlinear load whose complex impedance in each state varies with the frequency and the input power. This paper illustrates a proper calculation of the tag power reflection coefficient for maximum power transfer by taking into account of the changing chip impedance versus frequency.

No abstract

This paper presents an inkjet printing capacitive microwave sensor for toxic vapor detection. The designed sensors were presented and fabricated with success. The experiments show sensitivity to ethanol vapor according to the S parameters. It is equal to 0.9 kHz/ppm and 1.3 kHz/ppm for the sensors based on 5 and 50 sensitive layers respectively. This sensor will be integrated into real-time multi-sensing platforms adaptable for the Internet of Things (IoT).

No abstract

Purpose -The purpose of this paper is to develop a wireless strain sensor for measuring large strains. The sensor is based on passive ultra high-frequency radio frequency identification (RFID) technology and it can be embedded into a variety of structures. Design/methodology/approach -Silver ink conductors and RFID tags were printed by the screen printing method on stretchable polyvinyl chloride and fabric substrates. The development of the strain-sensitive RFID tag was based on the behavior of the selected antenna and substrate materials. Performance of the tags and the effect of mechanical strain on tag functioning were examined. Findings -The results showed that large displacements can be successfully measured wirelessly using a stretchable RFID tag as a strain-sensitive structure. The behavior of the tag can be modified by selection of the material. Research limitations/implications -New tag designs, which are more sensitive to small levels of strain and which have a linear response will be the subject for future work. Tag performance under cyclic loading and in a real environment will also be investigated. Future work relating the investigation of practical applications and the system designing for the strain sensor will also be required. Practical implications -Printing is fast and simple manufacturing process which does not produce much waste or material loss. The sensor is a new application of printed electronics. It also provides new opportunities for system designers. Originality/value -The paper provides a new kind of wireless strain sensor which can be integrated into many structures (i.e. clothes). The sensor is a new application of printed electronics and it is made from novel materials.

No abstract