Johanna Virkki

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We present the simulation-based design of UHF RFID tags based on electro-textile antennas and analyze the impact of recurrent washing on their performance through measurements. The antennas were fabricated from silver plated stretchable fabric made of nylon and elastic fibers. We coated half of the tested samples with acrylic spray to compare the influence(More)
The embedding of radio frequency identification (RFID) tags into plywood boards will enable the identification and tracking of individual plywood boards and end products of plywood. Even more benefits can be achieved by adding sensing functions into these tags. We present tags that are embeddable inside plywood by direct inkjet-printing on pure birch(More)
Material choices in electronic devices have a huge impact on the environment. The use of environmental-friendly processes and renewable materials is a growing trend. We present the inkjet-printing of antennas for passive UHF RFID tags on wood, paper, and cardboard. We printed the prototype antennas without surface treatments. We evaluated the performance of(More)
This study focused on the reliability testing of tantalum capacitors. The objective was to develop efficient tests to examine the effects of temperature cycling on capacitor maximum voltage. A test according to the standard JESD22-A104D overlooks the fact that temperature changes often occur while the voltage is on. Capacitors were first tested according to(More)
Radio frequency identification (RFID) provides great potential for different Internet of Things (IOT) applications. In the future, material choices in these IOT devices will have a huge effect on the environment and thus use of renewable materials is a growing trend. In this paper, passive ultra high frequency (UHF) RFID tags were inkjet-printed directly on(More)
This study focused on the use of accelerated testing to find out why tantalum capacitors fail. Stress effects of humidity, temperature, and ripple voltage were examined in different combinations. Results show that a standard 85/85 test with combined enhanced moisture and temperature does not result in failure of tantalum capacitors in 2500 h. However, with(More)
In this paper, the parameters for inkjet-printing and photonic sintering of silver and copper nanoparticle inks on flexible polyimide substrate were studied by manufacturing simple line patterns. The results were then utilized to manufacture passive ultra high frequency (UHF) radio frequency identification (RFID) tag antennas on polyimide substrate. The(More)
Nowadays there is an increasing interest to add functionality in various products and versatile electronics manufacturing methods are needed for different applications. In this study, brush-painting of silver nanoparticle UHF RFID tag antennas directly on wood veneer and polyimide film substrates was examined. Two sintering methods, heat and photonic(More)