Blood-Separating Device Without Energy Source for Implantable Medical Devices

Coagulation of blood inside the implanted medical device is quite a critical problem to limit the lifetime. In this paper, we propose a microfluidic blood separating device using curved and branched channels. It utilizes centrifugal force on curved flow and separates blood flow into blood cell rich and blood cell poor ones at the bifurcation. Though it cannot separate the plasma from blood cells completely, the blood with small concentrations of blood cells will have low coagulatibity and extend the lifetime of the implant medical device. The device does not require any external pumps or valves, i.e., the system does not need any power sources but the blood pressure. We conducted experiments with a titanium foil which contacted to human whole blood with different hematocrit values for 7 days. The device was experimentally characterized with respect to the channel design. The former experiments suggested that lower concentration of blood cells helps avoiding blood coagulations, and the latter showed that the separation by our device is mainly affected by the flow rate and channel curvature.

A Precise Sampling Strip with Microstructures

This paper presents a precise sampling microstructure formed as a paper strip. We have been developing dialysis system that can be implanted into a human body as an artificial kidney. For the safe use of our artificial kidney, the patients' urine needs to be constantly monitored to detect the abnormal value of ion concentration essential for human life. We are conceiving the monitoring system based on sampling by a paper strip. In this study, we fabricated the strip consisting of slanted and interlocked micropillars for the sampling, known as synthetic microfluidic paper. The paper-like substrate can be fabricated with a well-controlled geometry and subsequently enables precise sampling. Through the conducted experiments, it was shown that synthetic microfluidic paper had better mechanical properties, showed more precision in sampling than paper filter as well as corresponding liquid holding capability to the paper filter. Our proposed paper-based sampling system is expected to lead to the development of minimally invasive ion monitoring system with quantitative sampling strip.

Enfold-type connecting system of artificial blood vessels for micro implantable dialysis device

This paper reports the connecting mechanism for the artificial blood vessels along with the recent development of the micro implantable dialysis device. Our group has been studying the micro implantable dialysis device, which will drastically improve the quality of life of dialysis patients. We expect to replace the device every couple of years, which will involve surgery. In order to simplify the surgery to reduce the load to the patients, we develop a connector for the artificial vessels, which allows the exchange of the device by low invasive surgery. The connector needs to be designed not to induce blood coagulation. We designed a connecting mechanism that enfolds the artificial vessels to allow blood to contact only to the surface of the artificial vessels. In order to verify effectiveness of the proposed connecting mechanism, we investigated the connector surfaces with SEM after blood circulation tests. Then, we evaluated blood coagulation capacity of the connecting system as well as the set of the connecting system and the micro dialysis device with respect to the activated partial thromboplastin time (APTT). No remarkable increase of blood coagulation at the connecting point was observed after 72 hours of blood circulation tests. Short-term experiments for 120 minutes to evaluate APTT showed a small decrease of APTT, which needs to be further investigated in a longer-term experiments.