Research On Prothrombin Time Detection System Based On The QCM Sensor

Recent years, QCM sensors become a research focus of biosensors field. Thebasic principle is that the sensitive components quartz crystal are highly respondedto the changes of the surface mass adsorption (Mass Effect) and the physicproperties of reaction system, such as viscosity, density, conductivity and so forth(Non-Mass Effect). A piezoelectric biosensor with a nanogram sensitivity could beconstructed through a reasonable structure designing and biological processing to thequartz crystal．In recent research, it has been widely used in many research fieldssuch as clinical diagnostics, molecular recognition, surface properties research,molecular film-forming process, poison research and so on. The coagulation systemis an important part of the blood system and its function is to maintain thephysiological hemostasis. Generally, coagulation system abnormalities accompanywith a variety of diseases such as hemophilia, stroke and so on. Therefore, in clinicalpractice, the coagulation system function inspection is necessary. There is a wideprospective application in coagulation time research using QCM sensors because ofits advantages such as real-time detection, high sensitivity, small occupying, low costand so forth.This research focuses on the development of the QCM sensor detection systemand has been built two sets of hardware system for analysis and comparison. Thefirst set of hardware system uses a microcontroller as the control module and adedicated timer for frequency measurement, dividing and beating10MHz QCM basefrequency signal, then by detecting the final difference frequency signal (about450KHz) to obtain the experimental result, This approach indirectly reduces theQCM-based frequency and then reduces the requirements for measuring instruments.The second set of hardware system uses FPGA as both control and frequencymeasuring module, directly measures10MHz QCM base frequency signal to obtainthe experimental result, this approach avoids the accumulated error generated fromdividing and beating QCM base frequency. Both of the two sets of hardware systemuse nixie tubes to display the real-time frequency variation and upload the data to thehost computer, and use MATLAB to draw a curve to observe frequency variation trends. Using VS2008development environment provides a humane interface toimprove the efficiency of experiments and make the system more integrity at thesame time.In this research, for the first set of hardware system, in gas phase, frequencystability could be±3Hz, in liquid phase, frequency stability could be±30Hz; thenfor the second set of hardware system, in gas phase, frequency stability could be±200Hz, in liquid phase, finally, frequency stability could be±200Hz; for the twosystems, conducting coagulation tests abtained the same trend, basically verified thefeasibility of the program.