Study On Integrated Microfluidic Biosensing System Based On Giant Magnetoimpedance Effect

Giant magnetoimpedance(GMI)effect is a kind of magnetic sensing effect driving by alternating current(AC)with the advantages of high sensitivity,low power consumption,small size,fast response speed,and no hysteresis.Nowadays,GMI effect has been applied into target detection,aerospace,electronic compass,magnetic anomaly detection and so on,besides,it has potential applications in the field of target biological sample detection in clinical medicine.Point-of-Care Testing(Po CT)enables detection and diagnosis of diseases rapidly and accurately using miniaturized devices.Designing and fabricating a Po CT equipment with high detection sensitivity,fast detection speed and portability is a development requirement for clinical medical diagnostic equipment.GMI biosensor has the advantages of high detection threshold and high detection sensitivity.There have been a few reports in biomarkers detection using GMI biosensors,but these detection methods have the disadvantages of complicated operation steps,large test errors and hard in achieving test repeatability,which is difficult to meet Po CT requirements.Integrated microfluidic biosensing chip has the property of small volume,simple operation and short detection time,therefore,it is necessary to design and fabricate an integrated magnetic microfluidic biosensing chip based on GMI effect to complete the detection of target biomarkers,which is possible to further realize Po CT by using GMI effect.The main researches of this thesis are as follows:1.Establish the theoretical model of contact measured meander-structure GMI sensor and non-contact measured GMI sensing system based on the theory of contact measured and non-contact measured GMI effect.The influences of magnetic permeability of magnetic core and the structure parameters of non-contact measured sensing system on the output response of non-contact measured GMI sensing system were calculated.Increasing the width of magnetic core,decreasing the thickness of magnetic core and increasing the turns of solenoid can improve the output response and sensitivity of non-contacted GMI sensing system.2.The fabrication process of meander-structured GMI sensor based on contact measurement was optimized.The fabrication technique of GMI sensor by using ultraviolet laser cutting method was proposed,which made the geometric parameters and performance of GMI sensor more uniform and reduced production time.The methods for contact measured GMI effect enhancement were investigated.The influence of magnetic field anneal direction was discussed.GMI effect achieved better in GMI sensor fabricated by longitudinal magnetic field annealed Co-based ribbon,and the magnetic field sensitivity reached higher after reducing the line width of GMI sensor.The meander structure GMI sensor fabricated by longitudinally magnetic annealed Co-based ribbon with the line width of 200?m achieved the optimal GMI effect under the applied magnetic field of 7 Oe and the maximum GMI ratio was 209.7%.3.The property and output response of non-contact measured GMI sensing system were experimental studied under different external field intensities and different driving AC frequencies.The influence of width and thickness of magnetic core,as well as the turns of solenoid on the output response of GMI sensing system were measured.The calculation results in theoretical model were verified by practical experiment,as a result,the magnetic properties and fabrication feasibility of non-contacted measured GMI sensing system were verified.A three-dimensional micro-solenoid GMI sensing system was microfabricated by Micro-electromechanical Systems(MEMS)technology.The output signal response difference between measured by contact method and non-contact method was discussed.In comparison with GMI effect measured by traditional contact method,the output response of integrated GMI sensing system was significantly enhanced.In addition,the influences of driving AC frequency,external magnetic field intensity and direction on the output response of GMI sensing system were measured.GMI sensing system had higher magnetic sensitivity under longitudinal external magnetic field and the optimum GMI ratio was 4360%.4.MB manipulation systems based on planar micro-coil and permanent magnetic array were designed and fabricated.Among them,micro-coil can apply a wide range and easily changed external magnetic field on MB,therefore,MB with different flow rates,types,geometrics and concentrations can be captured in the microchannel.Besides,permanent magnet array can apply a larger magnetic field strength and a large magnetic gradient,as a result,the capturing force of the MB in the microchannel is larger.An integrated microfluidic GMI sensing system was designed and fabricated to manipulate and detect MB based on the principle of MB trapping by planar coil.The trapping efficiency was measured with MB flow rate ranged from 2.5?L?min^-1 to 20?L?min^-1.The variation rules of output impedance,resistance and reactance ratio of GMI sensor were measured and analyzed before and after MB trapping,and the relationship between the concentration of MB and output signal was fitted.Furthermore,an integrated magnetic microfluidic chip based on the principle of MB trapping by permanent magnet array was designed and fabricated by MEMS technology.This chip has excellent magnetic properties and can capture and detect different concentrations of magnetic beads.As a resllt,the chip provides a basis for the measurement of magnetic beads labeled biomarker samples.5.A peelable biomarker detection method was proposed and fabricated based on the commonly used methods for biomarker detection using GMI biosensor.This method has the advantages of reusable,short distance between target biomarker and GMI sensor,simple fabrication and low price.Prostate specific antigen(PSA)was used as a target biomarker to complete immunoassay and detection in integrated magnetic microfluidic biosensing chip.The detection limitation was 0.1 ng?m L^-1 and the detectable concentration ranged from0.1 ng?m L^-1 to 20 ng?m L^-1.This integrated chip decreased redundant reaction steps,avoided manual intervention,reduced reaction time,improved the effectiveness of immunoassay response,reduced test error,and can be potentially applied to future Po CT diagnosis.