400 MHz kalınlık uzama modu rezonatörü kullanarak kan pıhtılaşması zaman ölçümleri

This thesis presents a novel blood coagulation time measurement methodology which requires as low as 1uL of whole blood. The method performs measurements using whole blood without plasma separation. In this regard, the whole blood sample is placed on the top surface of a fused quartz plate (glass substrate) where an ultrasonic transducer (operating in thickness mode) is fabricated on the bottom surface. The transducer utilizes a short burst of 400MHz compressional acoustic waves along the thickness of glass substrate. The location of the blood sample is aligned with the transducer; therefore, the reflected acoustic waves from the blood/quartz interface are captured and converted to electrical signals by the transducer. A Mason modeling of the transducer in frequency domain was expressed to show the changes of resonance frequency of the transducer for different samples, like air, water, and blood, alongside with a numerical modeling to show amplitude of acoustic waves propagating inside the transducer in time domain. The acoustic impedance of the blood changes due to the coagulation process. This affects the reflection coefficient and amplitude of the reflected waves from the blood/quartz interface. A theoretical model was developed to show dependency of the acoustic waves amplitude to the reflection coefficient. Thus, the blood coagulation time was determined by monitoring the reflected acoustic waves amplitude. The transducer was made of 8um thick of sputtered Zinc Oxide (ZnO) thin-film that is operating at approximately 400 MHz TE (Thickness Extensional) mode. In the experiments, whole blood sample was used without any preparation. The method was tested using citrated blood with calcium chloride and activated partial thromboplastin (aPTT) reagents. We observed that aPTT coagulation times lengthen from 25 sec. to 47 sec. with the addition of heparin. The proposed method has a potential to be used in a disposable low cost portable coagulation time measurement cartridge for patient self-testing. The measurements were performed by collecting the amplitude of the reflected waves versus the time at specific frequency (400MHz); however, another possible way could be using a simple oscillator and a digital counter to track the resonance frequency and quality factor of the transducer versus the time. This will further reduce the cost and size of the proposed method. Nevertheless, this transducer has a potential to be used for characterizing liquid samples' parameters like viscosity, if it is operated in frequency domain and the input impedance is being tracked. This could be used for the applications where the lower volume of an expensive drug or chemical to be tested, is mostly desired.