The Development And Experimental Study On Implantable Biofuel Cell For Medical Devices

The implantable devices have been widely used in the medical and medicine fields, and most of them take the lithium cell as the power source, however, there are some shortcomings of this type of cells, such as insecurity of implantation and non-renewable. This prompted national researchers to study and development the new alternative cells. At present, there are a lot of plans, but the most concerned one is the implantable medical bio-fuel cell that uses the physiological body fluid as the fuel.Concerning about the design of this type of implantable bio-fuel cell for medical devices, the plate structure and the drum-type structure have been presented, and respectively studied the top-bottom assembly structure and the left-right assembly structure of the plate electrodes, and the single-walled vertical semicircle assembly structure, the single-walled horizontal semicircle assembly structure and the multi-walled concentric assembly structure.Considering the electrode processing and the test result, the top-bottom assembly structure of the plate structure has been finally determined. This structure enables the electrode catalase and the electrolyte (glucose reaction solution) to contact sufficiently, and it is also easier to process the electrode and experiment. Then, prepared the experiment electrode, comparing the performance of the materials of the electrode, such as ceramic, the non-corrosive metal, the carbon electrode that has reliable performance, low cost and easier to make was finally chosen. In order to achieve the small-scale design of the electrode device, the traditional proton exchange membrane has been canceled, instead, between the anode and cathode, the insulation hydrophobic membrane has been put into it, which is able to prevent the short circuit by direct contact of the two electrodes, and filter the plasma in the reaction solution selectively. This type of fuel cell makes use of the human body fluid (mainly of blood) as the basic reaction solution, so the basic condition of the body fluid must not be neglect, generally, in the human body, the content of the blood glucose is 0.1% -0.2% , the body temperature is about 37 o C, and the pH value of the body fluid is 7.34-7.45. Without considering the influences of other factors of the blood, the feasibility of"generating electricity"in the human body fluid has been theoretically confirmed.Generating electricity by human body fluid, the main cost is the glucose in the blood, so choosing the reaction enzyme is the important to the study. The considerations of the choosing the enzyme are as the following: first, this enzyme should be harmless to the human body; second, the product of the chemical reaction between the enzyme and the glucose should be harmless to the human body; at last, it is easier to compose and purchase. According to these points, the glucose oxidase (GOx) was made as the anodic catalase, and the bilirubin oxidase (BOD) was made as the cathodic catalase. The equation of the anode is: D - glucose(→|(GOx))δ-gluconolactone+2H⁺ +2e^-, and the equation of the cathode is: O₂ + 4H⁺ +4e^-→H₂O. The glucose in the blood was oxidized by the Gox of the anode, and its production glucolactone can be decomposed by the metabolism. The bilirubin can be deacidized by the BOD of the cathode, and its production biliverdin can also be decomposed by the metabolism. After determining the enzyme, the electro-catalytic layer on the surfaces of the electrodes should be taken into the consideration, theoretically, the electro-catalytic layer on the surface of the anode is consist of GOx, Redox Polymerâ… , and PEGDGE, and their weight percentages were 39.6% ,59.5% and 0.9% . there are two plan of choosing the electro-catalytic layer of the cathode, one is Mv-BOD plan , whose weight percentages were 44.6% Mv-BOD, 48.5% Redox Polymerâ…¡, and 6.9% PEGDGE; the other one is Tt-BOD plan, whose weight percentages were 44.4 % Tt-BOD, 49 % Redox Polymerâ…¡, and 6.6% PEGDGE.Based on the theoretical research, the invitro test can be conducted,the dicyclopentadienyl iron has been made as the substitute for it as the cathode. Use the polyamide gelatin mixture as the gap materials of the electrodes, and the plastic board was made as the packing of the electrodes. The purpose of the experiment is measuring the output current and output power of the fuel cell, meanwhile the continuous generation time should be also recorded, which is the preparation for the single factor test. According to the result of the basic test, divide into 3 groups into the single factor test, and observe the influence of the different concentrations of the glucose reaction solution on the output current and output power, in the cases of the concentrations of 0.1% , 0.2% , 2% , and 5% , then observe the influence of the different temperatures of the glucose reaction solution on the output current and output power, in cases of the temperatures of 36 o C, 36.5 o C, 37 o C, 37.5 o C, 38 o C, 38.5 o C, 39 o C, 39.5 o C, 40 o C, 40.5 o C, 41 o C, 41.5 o C, and 42 o C, and then observe the influence of the different pH values of the glucose reaction solution on the output current and output power, in cases of the pH values of 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, and 7.4. Finally, classify the above experiment datum, and the current and the power curves were plotted, analyze the experiment datum, and the got its changes. It is special to explain that the influence of the physical characteristics of the glucose oxidase on the output current and output power must be taken into the consideration.The theory and the test result of this subject is the initial step for the systematic study on the medical fuel cell, with the in-depth study, there would be more better design and test for it; and with the design optimization, the vitro simulation experiment could be conducted in the vitro blood of organisms, such as the bovine blood, human blood; the subcutaneous implantation test can be conducted in the living animal; and finally achieve to implant into the human body as the power supply.