Impedance Analysis of Blood Coagulation by Prothrombin Time Assay in a Miniature Device

In this paper, we present a microscale impedance-based technique for detecting different levels of blood plasma coagulation triggered by tissue factor thromboplastin. Impedance-based detection relies on measuring changes in the ac impedance between two electrodes due to the formation of favorably insoluble fibrin after treated with thromboplastin. Both gold and carbon parallel electrodes were tested and the optimum operating frequency for most sensitive coagulation detection was investigated. Micro fabricated gold electrodes could be used to detect the impedance difference between different levels of plasmas and the result was compared with optical measurement. A peculiar conductance maximum occurs at the optimal frequency for carbon electrodes and is a sensitive indicator of blood coagulation. Our optimized small electrode sensors are ideal for point-of-care applications.