A 0.5 mm2 0.31 V/0.39 V 28 nW/144 nW 65 nm CMOS Solar Cell-Powered Biofuel Cell-Input Biosensing System with PIM/PDM LED Driving for Stand-Alone RF-Less Continuous Glucose Monitoring Contact Lens

This work presents the first solar cell (SC)-powered biofuel cell (BFC)-input biosensing system with hybrid pulse interval modulation (PIM) and pulse density modulation (PDM) LED driving capability for stand-alone RF-less continuous glucose monitoring (CGM) contact lenses, which allows diabetes patients to obtain CGM level information without any external devices. Power supply from on-lens SCs can eliminate the necessity of wireless power delivery, and LED implementation can eliminate the necessity of wireless communication. By employing the BFC-input approach instead of using a power-hungry potentiostat, power consumption was reduced. The measured power of 28 nW/144 nW at PIM/PDM mode with a 0.31 V/0.39 V supply voltage can be managed by the on-lens SCs, enabling a fully stand-alone operation under office-room ambient light.

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.