A Differential Capacitive Viscometric Sensor for Continuous Glucose Monitoring
The development of glucose micro sensors for clinical use is driven by the aim of automatic blood glucose normalization in diabetic patients. An improved affinity viscometric sensor for continuous glucose monitoring (CGM) is presented by using a micro-ele
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Abstract The development of glucose micro sensors for clinical use is driven by the aim of automatic blood glucose normalization in diabetic patients. An improved affinity viscometric sensor for continuous glucose monitoring (CGM) is presented by using a micro-electro-mechanical system (MEMS) with a differential capacitor. A numerical model using Reynolds equation is used to simulate the dynamic response under different viscosities, and the relationship between capacitance and viscosity is revealed. Compared to the previous version presented by Columbia University, the sensor designed in this paper has enhanced the capacitor by introducing a differential capacitance, which also avoided volume changes of the air and polymer solution chambers during the vibration, increasing the linear range of the sensor. In addition, the simulation results show that the sensor can be driven by a Gaussian Pulse resulting in a significant power saving, when compared to a sinusoidal excitation. Keywords Continuous glucose monitoring • Biosensor • Differential capacitance • Viscometer
1 Introduction The development of glucose sensors for clinical use is driven by the aim of blood glucose normalization in diabetic patients [1]. Close monitoring of daily blood sugar levels reduces the risk of diabetes-related complications by allowing timely identification and correction of hyperglycemia as well as hypoglycemia, a condition that typically results from excessive insulin uptake or inadequate glucose intake.
Z. Yang (*) • M. Wang • Y. Bai • X. Chen School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou, China e-mail: [email protected] W. Wang (ed.), Mechatronics and Automatic Control Systems, Lecture Notes in Electrical Engineering 237, DOI 10.1007/978-3-319-01273-5_111, © Springer International Publishing Switzerland 2014
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This can be most effectively achieved by continuous glucose monitoring (CGM), which involves continuous measurements of physiological glucose levels. There are two types of CGM devices that have been developed. The first one is an electrochemical method, including enzymatic or non-enzymatic reactions [2]. Electrochemical methods are capable of sensitive and specific glucose detection. However, the irreversible consumption of glucose in the electrochemical detection induces a potential change in the equilibrium glucose concentration in the tissue and thus affects the actual measured glucose level. In addition, the rate of glucose consumption is diffusion limited [3]. This lack of reliability has been severely hindering CGM applications in relation to practical diabetes management. Another type of CGM is a physical method, in which the glucose is not consumed. More importantly, affinity sensing is considerably more stable, as the deposition of biological material on the implanted sensor surface results only in an increased equilibrium time, without any changes in the measurement accuracy. A widely used affinity sensing technique is based on concanavalin A (Con A
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