Femtosecond Laser Ablation Assisted NFC Antenna Fabrication for Smart Contact Lenses

Smart contact lenses (SCLs) have drawn substantial interest for continuous health monitoring applications. Even though most of the reported works utilize near-field communication (NFC) or inductive coupling for wireless powering and data transmission, developing a scalable and rapid fabrication technique for annular ring antennas confined in a small contact lens area is still an unsolved challenge. Here, femtosecond laser ablation is employed for the first time as a simple, single-step, and highly precise fabrication technique for NFC antennas using conventional flexible printed circuit board materials. Antenna lines with depth and width of 9 and 35 mu m are achieved, respectively. The antenna with a footprint of 19.5 mm(2) is characterized in biological solution followed by aging, and bending tests, and a frequency deviation of less than %1 is recorded. A real-life application is demonstrated by fabricating an SCL embedded with the antenna, an NFC chip, and an electrochemical sensor for wireless monitoring of glucose in artificial tear solution by a smartphone. The device could successfully quantify biologically relevant glucose concentrations ranging from 0.2 to 1 mM with a limit-of-detection of 66 mu M. In addition, device response to interfering molecules is less than +/- 1 nA, and the spike-and-recovery test is successfully demonstrated.