Recently our group developed 3D gel printer named "SWIM-ER" (soft and wet industrial material -easy realizer). Here we aim to improve the gel materials used for SWIM-ER system about the problems around free-shaping, transparency, and mechanical strength. To overcome these problems, we tried to use UV absorbers, AS150 (Nippon Kayaku Co.,Ltd.) and KEMISORB11S (CHEMIPRO KASEI Co.,Ltd.) and found the latter absorber kept transparency well. We improved the maximum tensile stress about 2 times and the maximum tensile strain about 4 times by changing the kind of cross-linker from methylene bis-acrylamide (MBAA) type to diethylene glycol dimethacrylate (DEGDMA) type. We also found that the maximum tensile stress was improved about 1.3 times by changing the blend ratio of 1st gel powder and 2nd gel solution in the preparation of particle-double network gels (P-DN gel). Based on these two improvements, we 3D-printed the transparent and hollow structure of the high strength gels with the maximum tensile stress of 0.5 MPa, which will be comparable to the maximum tensile stress of living organs like the stomach and small intestine in our body.
Submersible research vehicles and autonomous underwater vehicle (AUV) have been used for observation of underwater conditions, in addition to the technique of fixed-point observation. However, such research vehicles and conventional AUV are difficult to control, are expensive, and are usually made with nonbiodegradable materials such as metals. In contrast, jellyfish is the most efficient swimmers, traveling for long distance with saving energy by drifting in the ocean, its body can be decomposed after death, and safe for surrounding creatures. Therefore, we are developing the jellyfish-mimic AUV. In this study, we report a silicone-based hydraulically-driven soft actuator that can make a bending motion of umbrella-shaped bell of artificial Jellyfish. The behavior of the actuator in salt water was evaluated by image analysis, and the shrinkage factors of gel robots were compared with that of real jellyfish. Consequently, we have concluded there is a possibility that this actuator can reproduce jellyfish movement.
Medical doctors use artificial blood vessels and organ models, which are usually made of plastic, to explain operations to students, or patients awaiting treatment. However, there are some problems such as the high cost of making the model and there is not a realistic feel because the model is hard. These problems can be solved using soft and wet material for instance gel. Gels are materials with unique properties such as transparency, biocompatibility, and low friction. In recent years, high strength gel has been developed and is expected to be applied in medical fields in the future. Artificial models of gel can be produced by 3D gel printers. Our group has been developing a 3D gel printer with 1mm precision in printing, but the shape, size and mechanical strength are not sufficient for medical models. In this study, we overcome these problems and make a gel model which is transparent, mechanically strong with a fine shape. The strength and molding accuracy is improved by changing and preparing the cross linker and ultraviolet absorber. We conducted mechanical and molding tests to confirm that the gel material properties improved.
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