Future welfare and healthcare applications require wearable radio-frequency identification (RFID) tags where the tag antenna is an integral part of clothing and endures repeated stretching. In this study, wearable passive ultra-high-frequency (UHF) RFID tag antennas were fabricated from silver-plated stretchable fabric and by screen printing them on non-conductive, stretchable fabric. The reliability of the tags was studied by stretching them repeatedly from the initial length of 10 cm to 13.5 cm, up to 200 stretching cycles. According to our results, the electro-textile tags achieved read ranges of 6.5 meters, also after the 200 harsh stretches. The screen-printed tags initially achieved read ranges of 9.5 meters and after the 200 stretches the read ranges were only 2.5 meters shorter, that is, still about 7 meters. These measurement results and the strengths and weaknesses of both types of wearable tags are discussed in this paper.

We present a wearable passive UHF RFID tag based on a slotted patch antenna comprising only textile materials (e-textile, textile substrate, and conductive yearn). As a novel manufacturing approach, we realize the patch-to-ground and antenna-to-IC interfaces using only conductive thread and a sewing machine. We outline the electromagnetic optimization of the antenna for body-worn operation through simulations and present a performance comparison between the e-textile tag and a tag produced using regular electronics materials and methods. The measured results show that the textile tag achieves the electrical performance required in practical applications and that the slotted patch type antenna provides stable electromagnetic performance in different body-worn configurations.

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.

We present embroidered antennas and interconnections in passive UHF RFID textile tags and test their strain reliability. Firstly, we fabricate tag antennas on two different stretchable fabric substrates by five different embroidery patterns and choose the most stretchable ones for testing. Next, the tag ICs are attached by sewing and gluing, and the tag reliability during repeated stretching cycles is evaluated through wireless measurements. Initially, the chosen tags achieve read ranges of 6–8 meters and can strain up to 140–150% of their original length. After 100 stretching cycles to 80% of their maximum strain, the read ranges of the tags with glued interconnections are similar to the initial values. In addition, also the read ranges of the tags with sewed interconnections are still more than 70%–85% of their initial values. However, some challenges with the reproducibility need to be solved next.

We present the possibilities of 3D direct-write dispensing in the fabrication of passive UHF RFID graphene tags on a textile substrate. In our method, the graphene tag antenna is deposited directly on top of the IC strap, in order to simplify the manufacturing process by removing one step, that is, the IC attachment with conductive glue. Our wireless measurement results confirm that graphene RFID tags with printed antenna-IC interconnections achieve peak read ranges of 5.2 meters, which makes them comparable to graphene tags with epoxy-glued ICs. After keeping the tags in high humidity, the read ranges of the tags with epoxy-glued and printed antenna-IC interconnections decrease 0.8 meters and 0.5 meters, respectively. However, after drying, the performance of both types of tags returns back to normal.

Passive RFID technology enables versatile energy-and cost-efficient wireless platforms. We present passive UHF RFID tags integrated into normal work gloves for wearable RFID applications. The tags were designed to be functional throughout the global UHF RFID frequency range. The use environments of work gloves are challenging, for example due to moisture and mechanical stresses, which means the glove-integrated solutions have unique reliability issues to consider. We introduce 3D printing of a flexible thermoplastic material directly onto the glove and embed electro-textile antennas and RFID microchip components inside the 3D-printed structure. This manufacturing method solves the above-mentioned reliability challenges and enables the practical use of glove-integrated passive RFID tags. The performance of the fabricated glove-tags is firstly evaluated on a male test subject in an EMC room and in an office environment. Based on the wireless measurement results, the read ranges of the glove-tags are around 2-3 meters throughout the frequency range of 800-1000 MHz. These results meet the requirements of many practical applications of glove-tags. Further, these glove-tags are found to endure extreme moisture and mechanical stresses, which supports their use in versatile use environments. Finally, the developed glove-tags are successfully tested in actual use situations for identification and access control. These results are very promising, especially considering the cost-effectiveness and the easiness of tag integration into different types of gloves.