Study Of Minimally Invasive Glucose Meter By Interstitial Fluid Transdermal Extraction

Blood glucose monitoring is the prerequisite and foundation for diabetes therapy. Compared with invasive blood glucose monitoring, minimally invasive blood glucose monitoring does not require invasive blood sampling. Meanwhile, it is closer to clinical application than non-invasive blood glucose monitoring. The minimally invasive glucose monitoring technologies include two types, implantable glucose sensors and glucose monitoring methods based on transdermally extracted interstitial fluid. The implantable glucose sensors’lifetime is short and their measurement results are not accurate. The minimally invasive blood glucose monitoring meter based on transdermally extracted interstitial fluid is studied in this thesis.The amount of interstitial fluid extracted by the minimally invasive blood glucose monitoring method is very small. In order to measure the glucose concentration, the collection, volumetric measurement, transport, and concentration measurement of the interstitial fluid with tiny volume are required. The miniaturized, integrated and automated glucose monitor based on transdermally extracted interstitial fluid is studied in this thesis utilizing a microfluidic chip for transdermal interstitial fluid extraction and a micro-mechanical glucose sensor which were developed by our group.The major achievements of this work are as follows:(1) The overall structure of the minimally invasive glucose meter based on transdermally extracted interstitial fluid is designed. At first, low-frequency ultrasound is used to increase the skin permeability. And then the interstitial fluid is transdermally extracted and collected from the subcutaneous by vacuum. Finally, the glucose concentration of the obtained interstitial fluid is measured.(2) The interface features of the minimally invasive glucose meter based on transdermally extracted interstitial fluid are designed. The gas channels and the control circuit interface of the micro-Venturi tube, the micro-volume sensor with four pairs of electrodes and the pneumatic valves are designed. In addition, the circuit interface of the micro-glucose sensor is designed.(3) The hardware of the minimally invasive glucose meter based on transdermally extracted interstitial fluid is designed. Digital Operations controller circuit, analog signal acquisition and processing circuit are designed, including power supply circuit, keyboard circuit, display circuit, signal acquisition and control circuits.(4) The software of the minimally invasive glucose monitor based on transdermally extracted interstitial fluid is designed. The program is written to realize the automatic control of the microfluidic chip and the micro-glucose sensor. Utilizing the program, the interstitial fluid transdermal extraction, volumetric measurement and collection functions, the defined volume of normal saline injection function, and the glucose concentration measurement function of the diluted interstitial fluid are realized. The functional modules of the program include the initialization module, LCD display program, keyboard program, AD collection procedures, data storage procedures, USB communication procedures, micro-pump and micro-valve control program.(5)The interstitial fluid transdermal extraction device is tested through pig skin. The performance and the measurement accuracy of the interstitial fluid transdermal extraction device are verified. The maximum relative deviation of the concentration measurement results is 16%.