| Stretchable RFID tag is an emerging electronic device combined stretchable electronic technology with RFID technology, and has been broadly used as stress sensors in various fields such as biomedical applications and tire condition monitoring. When stretched, outside stress change causes electric signal changes of the tag antenna, which makes it a sensitive stress sensor. The challenge is how to make a stretchable RFID tag with stable working frequency and excellent electrical properties during stretching. UHF RFID tag is one of the most widely used tags, by improving the structure of the tag antenna, a stretchable UHF RFID tag with stable working frequency has been designed and fabricated using liquid metal material. Finite element simulation is used to confirm the accuracy of the antenna design. The major work can be summarized as follows:As the most commonly used antenna type in UHF RFID tag, dipole antenna is chosen for the research. Serpentine structure has been proposed for the dipole antenna design to achieve stable resonant frequency during stretching. Finite element simulation is conducted to verify the design.Liquid metal is chosen as conductive material for fabricating the dipole antenna, multiple groups of stretchable serpentine dipole antennas with different aspect ratio have been prepared, their electrical properties under different mechanical stress is tested to study effects on the antenna properties caused by change of the aspect ratio. Besides, influence of other factors on the antenna frequency change has also been studied.A method for designing stretchable tag antenna is proposed, effects on the tag performance of the number of serpentine dipole antenna units is studied. According to the calculated range of the aspect ratio, specific deign parameters is acquired by simulating the working frequency change of the tag antenna. Ultimately, a stretchable RFID tag is fabricated, it can maintain relatively stable working frequency even if tensile strain approaches to 50%.In summary, an improved structure for the stretchable liquid metal dipole antenna has been put forward. Influence of other different parameters on the frequency change of the dipole antenna when stretched has been researched as well. The improved dipole antenna structure is applied in design of the RFID tag antenna, a stretchable RFID tag with stable working frequency is finally obtained. |
