Research On Targeting Magnetic Field Generator

Magnetic targeted drug delivery system is one of targeted drug delivery systems,and is becoming a hotspot in recent years. Magnetic targeted drug delivery system is designed to make the magnetic particles arrive at the target area and oscillate release.Guide magnetic is requested to has a certain magnetic field intensity and magnetic field gradient as well as distribute in space ,so that it is in favour of the magnetic drug oscillation absorption. The magnetic field gradient is not very hight in the current targeted magnetic field generator research,and it only exists in both targeted poles,not in spatial distribution. For this reason,the paper proposes a research plan of magnetic field generator which has good magnetic field gradient and spatial distribution.The work of this paper are mainly as follows:①The paper expounds various ways of producing magnetic field ,and finds that the electromagnetic coils is more suitable for targeting researches by comparative analysis.②By the understand of the characteristics of magnetic materials and analysis of the requirements for the soft magnetic materials , the paper proposes to use industrial silicon steel sheet as magnetic pole materials and pure iron as magnetic yoke materials.③Based on the requirement of magnetic field gradient , the paper proposes to use capacitance to clamp the front edge and trailing edge of transmitting coils.Because of the requirment of fast shutoff,the paper use the faster shutoff speed power field effect transistors MOSFET as switch. The volume of storage battery is big and not convenient for moving,so we design a voltage source circuit which has a output current about 5 amp. The paper uses PSIM simulation software to analysis the main circuit,verifies the feasibility of the main circuit.④The paper designs the drive circuit.Because the top bridge arm in main circuit is floating ground,so the circuit requires independent power supply.For the purpose of reducing number of supply power sources, the paper proposes the solution of bootstrap drive circuit. The bootstrap capacitance is very important in bootstrap circuit,so we analyse and calculate the value of bootstrap capacitance.The experiments were performed for the designed drive circuit,and the waveform of measurement complies with the driver requirements of power field effect transistors MOSFET.⑤The paper designs the contorl circuit.In order to make the output pulse signal duty cycle arrive at fifty percent,the paper uses D flip-flop to design half frequency circuit and realizes the corresponding drive control signals. The paper also designs the corresponding program flowchart to realize that switches control frequence tap position and the coil controlled ports conduct successively.⑥The paper gives a comparison analysis for different sorts of current waveform,and determines the dual polarity delay square-wave to be more suitable for targeted therapy. The paper gives a qualitative analysis to the magnetic particles movement and force analysis in dual polarity delay sqare-wave,and knows why the dual polarity delay sqare-wave is in favour of the drug oscillation release. The paper applys Protel software to design PCB board ,and debugs the experimental board. The test results prove that the designed magnetic field generator in this paper solves the problem of low magnetic field gradient, which provides a better base for the product ulterior exploitation.⑦Finally, the summarization and prospect of this study are proposed.