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Design of a Microfluidic System for Continuous Glucose Measurement, as well as Fabricating and Experimentally Testing the Biosensor

Najmi, Armita |

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53070 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Saeedi, Mohammad Saeed; Kazemzadeh Hannani, Siamak; Shahrokhian, Saeed
  7. Abstract:
  8. Diabetic patients, unlike other people whose blood glucose vary in a limited and normal range, encounter hyperglycemia and hypoglycemia, so their glucose level should be measured periodically and kept in the normal range. The aim of this research is to design an implantable integrated microfluidic system in order to regularly measure the glucose level in the human body, using the microdialysis method. The main compartments of this system are a micropump, array of hollow microneedles at the base of them located semipermeable membranes, the channels of dialysis fluid and an electrochemical sensor for measuring the glucose level. The micropump of this system is designed and simulated based on piezoelectric type of actuation. The selected materials and the dimensions of the compartments of this micropump are adopted and designed in a manner that the micropump can supply the necessary flow rate with the lowest needed electrical potential, also the size and thickness of the micropump to be so small not to bother the patient. An array of hollow microneedles with the penetration depth of 150μm is considered to sample the glucose of the human body. Since the penetration of these microneedles are less than the depth of the location of nerve tips from the skin surface, they do not cause any pain to the patient. By modeling the porous texture of the skin and the simulation of a two-phase fluid flow, it is concluded that, inserting the microneedles into the skin, interstitial fluid flows upward in the needles due to the surface tension and reaches to the semipermeable membranes. Glucose of the interstitial fluid diffuses into the dialysis fluid through semipermeable membranes. The arrangement and the number of microneedles, the dimensions of dialysis fluid microchannels, the flow rate of dialysis fluid and the thickness of the membranes were selected so that the greatest possible recovery factor can be achieved while system's size, time delay and the consumed dialysis fluid kept at the best minimum possible. It was also tried to select the dimensions of microchannels entrances so that the flow rate of the dialysis fluid can be kept the same in all of them. In the design and fabrication of the nonenzymatic sensor, it was taken into consideration, first the deposition of nanostructures on the glassy carbon electrode and experimental tests by arranging this electrode in the three-electrode cell. It was tried to achieve the optimum electrical potential and the optimum time necessary for depositing the nanoparticles of Pt-Ni alloy on the surface of the working electrode using the electrochemical method. The effect of nanocarbon sublayers such as using of carbon nanotubes and graphene, as well as the optimum ratio of Pt-Ni alloy were investigated by accomplishing the experimental tests of cyclic voltammetry and amperometry in order to increase the sensitivity of the sensor. Finally, depositing the optimum nanostructure on the screen printed electrode and finding the optimum electrical potential for amperometry measurement, the calibration curve of the electrical current versus glucose concentration was achieved by flowing the dialysis fluid into the microchip containing three working, counter and reference electrodes. Having high sensitivity and wide linear range as well as noninterference with other existing electroactive species inside the interstitial fluid are the properties of this sensor. The fabricated sensor also has high repeatability and reproducibility and preserves its stability by time passing
  9. Keywords:
  10. Glucose ; Nonenzymatic Sensor ; Semi-Permeable Membrane ; Dialysis Fluid ; Interstitial Fluid ; Hollow Microneedles ; Piezoelectric Micropump

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