On-Chip Glucose Sensor With a Microstructure Gap for Sensitivity Enhancement

On-chip photonic glucose sensors are important for future development in biosensing, disease diagnosis, and environmental monitoring, where a compact and high-sensitivity sensing head is the key component. In this paper, we demonstrate a high-sensitivity sensing head for glucose concentration monitoring using a Mach-Zehnder Interferometer (MZI) formed polymer waveguides with a microstructure gap on the sensing arm. By optimizing the length and gap of the sensing arm, the sensor achieves a sensitivity of glucose concentration of 2.37 nm/(g/L) (corresponding to 2651 nm/RIU) with a gap length of only 50 μm. To validate the idea, we fabricate the on-chip sensor using an in-house microfabrication process. The fabricated sensing chip shows a sensitivity of glucose concentration of 2.32 nm/(g/L) (corresponding to 2554 nm/RIU) with low-temperature crosstalk, as the temperature sensitivity is only 31 pm/°C. The proposed on-chip sensor offers high sensitivity, low crosstalk, and low cost, making it a promising candidate for detection applications requiring a high-sensitivity sensing head.