In this letter, we establish a new type of passive ultrahigh-frequency (UHF) radio frequency identification (RFID) technology-based sensor with a referenced readout for moisture. We introduce the sensor system, which consists of a sensor tag and a reference tag. In a highly moist environment, the sensor tag, which is fabricated by embroidery and three-dimensional (3-D) printing, permanently changes its shape from flat to curved, which then influences its wireless performance. By recording the backscattered powers of the sensor tag and the unaffected reference tag, the presence of moisture could be detected. Based on our preliminary results, when the mean value of ΔP% was higher than 0.8, the sensor system indicated exposure to a high-moisture environment. Our moisture sensing system can provide cost-effective zero-energy monitoring of moisture exposure for versatile application fields.

This paper introduces a prototype of ClothFace technology, a battery-free textile-based handwriting recognition platform that includes an e-textile antenna and a 10 × 10 array of radio frequency identification (RFID) integrated circuits (ICs), each with a unique ID. Touching the textile platform surface creates an electrical connection from specific ICs to the antenna, which enables the connected ICs to be read with an external UHF (ultra-haigh frequency) RFID reader. In this paper, the platform is demonstrated to recognize handwritten numbers 0–9. The raw data collected by the platform are a sequence of IDs from the touched ICs. The system converts the data into bitmaps and their details are increased by interpolating between neighboring samples using the sequential information of IDs. These images of digits written on the platform can be classified, with enough accuracy for practical use, by deep learning. The recognition system was trained and tested with samples from six volunteers using the platform. The real-time number recognition ability of the ClothFace technology is demonstrated to work successfully with a very low error rate. The overall recognition accuracy of the platform is 94.6% and the accuracy for each digit is between 91.1% and 98.3%. As the solution is fully passive and gets all the needed energy from the external RFID reader, it enables a maintenance-free and cost-effective user interface that can be integrated into clothing and into textiles around us.

We present a passive ultra-high frequency (UHF) radiofrequency identification (RFID)-based strain sensor, which is designed for simple and efficient body movement monitoring. This RFID platform is fabricated from electro-textile materials and can thus be seamlessly integrated into our everyday clothing. The sensor platform has an integrated reference tag, in order to avoid the effects of reflections or external disturbances on the sensor tag performance. This sensor platform prototype has an on-body read range of 1 meter in a normal office environment with an off-the-shelf RFID reader. The wireless performance of the sensor tag has a significant change caused by arm elongation. Thus, the sensor functionality can be based on variation of the sensor tag's backscattered power percentage (P %). Based on the preliminary results achieved in this study, this passive and cost-effective sensor platform could be an efficient future way to turn human gestures into inputs for digital devices.

In this paper, we establish a new type of passive ultra-high-frequency (UHF) radio frequency identification (RFID) technology-based moisture sensor. The sensor system consists of a sensor tag and a reference tag to indicate exposure to moisture. The sensor tag is fabricated on a cotton substrate from conductive silver yarn and water-soluble polyvinyl alcohol (PVA) yarn. When the sensor is exposed to water, the PVA yarn will melt, which causes a permanent change to the tag antenna body and to the wireless performance of the sensor tag. By measuring the backscattered power strength difference, ΔP, the presence of moisture can be detected and recorded. When ΔP is below 0, the sensor system shows that it has been in a highly moist condition. Our PVA-based moisture-sensing system can provide cost-effective and maintenance-free monitoring of moisture exposure for versatile application fields.

This paper introduces a prototype of a low-energy high-temperature exposure sensor, which is a temperature-sensitive passive UHF RFID tag that bends forward when exposed to warm air. This “Bending Tag” design is based on a simple dipole antenna fabricated from an electro-textile material. The antenna has a 3D-printed substrate, which is constructed from a commercial Thermo Reactive Filament that gets soft when exposed to 50°C for 30 seconds, causing the tag to bend forward and curve. The sensor tag initially has a read range of more than 6 meters throughout the global UHF RFID frequency band. After bending, there is a significant decrease in the read range (to around 2–3 meters), which is caused by the changed backscattered power of the sensor tag. In an office environment, the backscattered power changes from −36 dBm to −43 dBm. The change in a sensor tag-reference tag system as dP% is approximately 70%. Based on these initial results, our bending tag can be further developed to work as a cost-effective low-energy sensor for monitoring high-temperature exposure.