Published papers

© 2018 IEEE. This paper describes automation of planar lipid bilayer formation by introducing a stepping motor to a microfluidic device. Planar lipid bilayers or lipid vesicles are useful to understand biological reactions and to investigate the interaction between lipids and proteins. Therefore, to acquire large amount of the information, high-throughput production of planar lipid bilayers or giant vesicles (GVs) is necessary. The droplet split-and-contact method, which enhances the efficiencies of both planar lipid bilayer formation and GV generation, needs to be automated for increasing the throughput. Previous droplet split-and-contact devices were manipulated manually; hence, the influence of manipulation on planar lipid bilayer formation was not evaluated quantitatively. First, to develop an automated system for generating asymmetric planar lipid bilayers, a stepping motor, which allows to control the angular speed of the rotor, is integrated into the droplet split- and-contact device (Fig. 1({b)). Next, we assessed planar lipid bilayer generation at various angular speeds and found the speed limit for bilayer formation. Finally, we generated asymmetric planar lipid bilayers that have different lipid composition on outer and inner leaflets using this automated device and confirmed the asymmetry of the planar lipid bilayers by generating GVs.

© 2018 Japan Institute of Electronics Packaging. Despite today's race for IoT application dedicated to home care, and healthcare service, remote analysis of urine, one of the best bio-marker, remains quite challenging and can be improved. This paper demonstrates an automatic urine monitoring device using the capillarity effect inside a channel and cross-selectivity principle to create a modular and daily analysis solution. The developed device was tested on simulated urine and successfully determined its basic composition (ionic concentration and color). We finally proposed a realistic use-case for heatwave prevention in Japan by connecting our device with a ESP32 module to bring the daily result to a healthcare application.

© 2018 IEEE. Here, we demonstrate, for the first time: the self-digitization, i.e. spontaneous formation, of microdroplets during the imbibition of paper; the on-demand merging of individual microdroplets in paper; and the on-demand ejection of individual microdroplets from the paper. Two technical novelties underlie these novel functions: the formation of free-standing synthetic microfluidic paper, i.e. a porous matrix of slanted and interconnected micropillars without bottom layer; and the hydrophobic surface modification of the paper. The ease of manipulation and the direct access to the microdroplets from the environment makes this an extremely versatile tool, with potential applications in liquid sample digitisation and microparticle generation.

© 2018 IEEE. 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.

© 2018 IEEE. This paper describes the development of a handheld device for long-term nanopore-based biosensing. Recently, membrane protein reconstituted in bilayer lipid membrane (BLM) has been applied for bio/chemical sensors because membrane protein intrinsically has a superior amplification mechanism. For mobile use of such devices, however, the bilayer requires mechanical robustness. Here, we propose a handheld BLM device aiming for a nanopore-based mobile sensor. BLM is formed at the tip of a glass capillary, which is contained in the solution trapped in a cup-like reservoir. This format achieved (i) formation of a sufficiently robust BLM for mobile use, (ii) solution exchange without rupturing BLM, and (iii) sustaining the small number of nanopores in the bilayer for accurate and long-term sensing. The handheld device successfully detected DNA translocations through the nanopores continuously for 75 minutes using 5 nanopores.

© 2018 IEEE. In this report, we experimentally investigated the blood hemofiltration capacity of a nanoporous dialysis membrane (poly(ether sulfone), PES) whose surface was modified with fluorine-doped diamond-like carbon(f-DLC). Surface modification of the nanoporous membrane without clogging the nanopores is challenging. In vitro experiments revealed that the modified membrane successfully exhibited water permeability of one-tenth of the untreated. In vivo experiments with ultra-small hemofiltration devices composed of f-DLC PES membranes using SD rats were also conducted for the first time. The results proved that the f-DLC coated PES membrane can be used for hemofiltration, which will extend the lifetime of microfluidics-based implantable artificial kidney.

© 2018 IEEE. We have developed a novel liquid metal based electrodes micro-array for the electrical stimulation of biological tissues with a direct liquid metal - biological tissue contact surface. This work presents for the first time an effort to introduce Gallium based liquid metal components to the field of implantable electrical stimulation systems. The electrical performance and overall integrity of the liquid metal open micro-channel electrodes were fully characterized and analyzed in regard of the properties of the liquid metal used, the surrounding environment, and the stimulation signal. Stable direct contact stimulation electrodes down to a width of 50 μm were successfully produced and tested in-vitro.

© 2018 Japan Institute of Electronics Packaging. Evaluations for the enfold connecting system of system is developed to reduce and simplify the maintenance surgery of the artificial organ.The connector is designed not to contact the blood directly and the artificial blood vessel enfolds metal pipe in connector. Thanks to this design, the biocompatibility of the connector is comparable with an artificial vessel. We confirmed the blood coagulate protein which form a thrombus at the joint point of the connector with SEM. And we also measured a potential of blood coagulation by activated partial thromboplastin time (APTT). We didn't find the remarkable increase of blood coagulation on the connecting point for 72 hours. And APTT decreased a little in the experiment of a blood circulation system with the connector but we can't conclude that the connector causes a blood coagulation from results for 120 minutes. Additionally, we measured a potential of blood coagulation by APTT about the micro dialysis device which is developed in our group. We conducted the micro dialysis device experiments as with the same method of the connector experiments of APTT. We did not observe the remarkable disease of APTT for 120 minutes about the micro dialysis device as well. However, we found that the hemolysis was possible to be occurred in the micro dialysis device.

© 2018 Japan Institute of Electronics Packaging. In this study, we successfully reduced the parasitic capacitance of PDMS-based flexible tactile sensors by decreasing the dielectric constant of PDMS. UV exposure changes Si-CH3 bonds in PDMS to Si-O, which leads to the low dielectric constant. This simple but effective method can be readily applicable to improve signal-To-noise ratio of PDMS-based flexible sensors.