Maximizing Energy Harvesting in Flexible NFC Antennas for Wearable Electronics
Discipline: Technology and Engineering
Subcategory: Electrical Engineering
Session: 2
Room: L'efant Plaza
Kevin Ahmad Moone - Norfolk State University, Virginia
Co-Author(s): Jarvis Turner, Norfolk State University, Virginia; Harikrishnan Muraleedharan Jalajamony, Norfolk State University, Virginia
Near Field Communication (NFC) technology has become a promising option for wearable electronics in recent years due to its ability for energy harvesting and secure short-range communication. NFC uses a loop antenna to communicate with nearby NFC-enabled devices or a dedicated reader through a 13.56 MHz RF communication frequency. Along with data transmission, the NFC tag’s energy-harvesting feature allows it to generate voltage from the magnetic field produced by the NFC reader. Low-power microcontrollers and sensors can be powered by this voltage, enabling battery-less applications.The design of a loop antenna plays a significant role in the energy harvested voltage and data transmission distance. We studied the energy harvesting properties of custom-made flexible antenna for maximum energy harvesting voltage and transmission distance. A custom-made flexible square loop NFC antenna was designed and simulated using Anysis HFSS software before fabrication. The antenna was fabricated on a flexible polyamide using silver ink, which has a dimension of 40 mm2, with 3 loops and a trace width and spacing of 1mm. The study was conducted with an ST25RX-NUCLEO-NFC06A1 NFC reader board and a custom-designed ST25DV16K NFC tag. The energy harvested voltage of the NFC tag was measured with different antenna reader pairing distances and antenna bending angles. A maximum of 3.4 V was measured when the antenna and reader touched each other. The harvested voltage decreased with increased pairing distance and became 0 after 7 cm. A bend test was conducted to study the possibility of a flexible antenna in wearable devices, where the NFC tag is needed to power low-power sensors and microcontrollers. The study reveals that the harvested voltage decreases when the antenna is bent from 0 to 90o. During this bending stage, the antenna was able to generate more than 2 V, which is sufficient for most low-power sensors and microcontrollers like ATSAMD21G18, which can work as low as 1.8 V. These studies reveal the feasibility of using flexible antennas in NFC-based battery-less applications. This flexible antenna design holds promise for various bendable wearables, such as smart masks and smart bandages, leading the way for innovative and energy-efficient wearable electronics. We are currently exploring the possibilities of fabricating suitable NFC antennas for wearable devices to maximize the data transmission distance and harvested voltage.
Funder Acknowledgement(s): This work was funded in part by the NSF grant # 2112595 CREST Center for Research and Education in Quantum Leap Science and Technology (CREQS). This project is also supported by the National Science Foundation: Award Number 2100930.
Faculty Advisor: Renny Edwin Fernandez, refernandez@nsu.edu
Role: I designed and tested the antenna part, which includes measuring the harvested voltage of ST25DV16K with the antenna. The harvested voltage was measured when changing the antenna pairing distance. I also tested the performance of the antenna at different bending angles.