I. Introduction
Continuous glucose monitoring (CGM) is essential for diabetes patients to keep glucose balance and prevent hypoglycemia which is a dangerous condition of low blood glucose level. Therefore, many systems have been designed to ensure low-cost and painless CGM. CGM systems integrated on contact lenses [1]–[3] to monitor tear glucose levels are preferable owing to low invasiveness and a good correlation between tear and blood glucose concentration. Some RFID-based prior studies [1], [3], employed wireless RF power transfer to operate the systems on a contact lens. However, an external device, such as smart glasses transmitting power at a distance of 15 cm [1] or 1 cm [3], is required, which degrades the comfort and eye health of the users.