1. Design and Fabrication
A WEARABLE CONTINUOUS GLUCOSE MONITORING SYSTEM WITH ELECTROCHEMICAL SENSOR MODIFIED BY GRAPHENE
Zhihua Pu1, Ridong Wang1, Jianwei Wu1, Haixia Yu2, Kexin Xu1 and Dachao Li1*
1State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, China,
2Tianjin Key Laboratory of Biomedical Detecting Techniques and Instruments, Tianjin University, China
Background
Experimental Results
Implantable enzyme electrode sensors are invasive and the life of them is short due to the foreign body reaction.
Glucose cannot be measured accurately by the implanted sensors due to the signal drift caused by the bioelectricity of human body.
It is still a big challenge to detect the hyperglycemia by the implantable enzyme electrode glucose sensors in clinics.
Effect of graphene
Objective
A novel wearable system including a microfluidic interstitial fluid (ISF) extraction chip and a three-electrode electrochemical sensor is fabricated for continuous glucose monitoring.
The system detects glucose externally which overcomes the drawbacks of the measurement inside the human body by the implantable enzyme electrode sensors.
Glucose measurement by the sensors with and without AuNPs when graphene is absent
Glucose measurement by the sensor with graphene and AuNPs
The reaction current signals of glucose in low levels cannot be distinguished by the sensors with or without AuNPs if graphene is absent, while it can be well identified when graphene is present.
Design and Fabrication
Effect of gold nanoparticles
Design and fabrication of microfluidic ISF extraction chip
A Venturi to provide driving force for both ISF extraction and fluid manipulation
Pneumatic valves to control the ISF extraction and collec-tion processes
Fabricated from five PDMS layers using micromolding techniques
Design and fabrication of the electrochemical sensor
3.6 times enhancement of the sensor sensitivity is obtained by depositing AuNPs onto the graphene layer, demonstrating the big improvement of the sensitivity of the sensor by depositing AuNPs.
Evaluation of the glucose sensor
The linearity range of glucose measurement by the electro- chemical sensor is 0~162mg/dL, and the limit of detection (LOD) is 1.44mg/dL (S/N=3).
The proposed electrochemical glucose sensor exhibits the potential of hypoglycemia detection in clinics.
10nm chromium and 100nm platinum were sputtered and patterned on the glass to form the three-electrode substrate.
Ag/AgCl RE: immersing the electrodes into 50mM FeCl3 for 50s after electroplating silver onto the middle electrode surface.
Surface modification of the working electrode
Graphene and AuNPs was employed to modify the WE surface to improve the glucose measurement resolution.
Conclusions
A wearable microsystem including a ISF extraction chip and an elec- trochemical sensor was fabricated for continuous glucose monitoring.
Graphene and AuNPs were employed to modify the WE surface of the sensor to improve the glucose measurement resolution.
The sensor can precisely measure glucose in the linearity range of 0~162mg/dL with the LOD of 1.44mg/dL (S/N=3), which exhibited the potential of hypoglycemia detection in clinics.
A single-layer graphene was transferred onto the WE surface.
AuNPs were electrodeposited onto the graphene layer.
GOD was electrochemical polymerized onto the surface finally.