Development of electrical powerless system for blood separation and coagulation time measurement

Background: In recent years, developing low-cost point-of-care diagnostics for the areas where the spread of disease is fast, and where resources are limited, is becoming a vital topic of research. In this study, a blood separation and the determination of blood condition without using power was studied. A powerless centrifuge using finger spinner for Red blood cell separation and a self-powered plasma coagulation time measuring device have been developed. The finger spinner was designed and made by 3D printer. After cells are separated, the plasma will be obtained. A self-powered micro-channel device which is able to generate electrical signals by using triboelectric phenomenon was developed. When fluid flows through a solid surface, potential difference between the liquid and the solid surface is generated by friction. The device can be used to determine the coagulation time of the plasma. When the coagulation happens, the induction potential will be decreased. Combined the finger spinner centrifuge and a self-powered micro-channel, a blood condition detecting system without power can be obtained. Methods: This study used 3D computer aided design (CAD) to design the finger spinner, and used 3D printer to make a four-arm finger spinner centrifuge to achieve blood separation without electricity. Then we used the triboelectric effect between solid and liquid, and combined with the design of the micro-channel and the gold electrode to form a system that can detect self-powered electrical signal when plasma flow in microfluidic channel. First, the sample was loaded in a syringe, and a stable flow rate is supplied through a syringe pump into the device. When the fluid flow in the micro-channel flow, because of the triboelectric effect, the charge is generated and accumulated at a thin dielectric layer covering on the electrode and channel wall. The voltage difference between electrode and the fluid was measured. In this study, we use different kinds of fluid to test, such as deionized water, glycerin with different concentrations, plasma, and plasma mixed thrombin. In the end, we collect different electrical signals by changing different viscosity to summarize the utility of the measurement wafer. Results: The results show that the four-arm finger spinner centrifuge has a better effect to centrifuge than the dual-arm finger spinner centrifuge. Through the result of glycerin with different concentrations and plasma mixed thrombin, the increase in viscosity and plasma coagulation leads the decrease of the voltage difference. Conclusions: In this study, the increase of the moment of inertia by weight design was investigated to improve the centrifuge effect for blood separation. For triboelectric effect at liquid-solid interface, the increase of the viscosity resulted in decrease of voltage difference. When plasma start to coagulate, the viscosity of plasma will decrease, and the voltage difference decrease.