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To examine the effect of early mobility (EM) on functional recovery after hip fracture surgery, and to investigate the potential factors that delay mobility.In this retrospective observational study, 110 hip fracture patients were divided into two groups according to the days between surgery and mobility referred to as the EM and the delayed mobility groups. Demographic data, perioperative data, functional outcomes, and discharge destination were compared statistically between the groups using univariate analysis and logistic regression analysis. As a sensitivity analysis, the factors associated with the timing of physiotherapy were also assessed.The EM group had significantly better walking ability and Barthel index (This study demonstrated that EM after hip fracture surgery was associated with improving functional recovery and home discharge rate, and early physiotherapy intervention was associated with EM.Early mobility on the first day after hip fracture surgery was associated with improving walking ability and independence of daily activities on postoperative days 7 and 14, as well as on the time to discharge to own home.Early mobility was specifically associated with the timing of physiotherapy intervention, the days from admission to surgery and the medical condition including perioperative anemia. In particular, patients who received surgery on the day before any holiday were significantly delayed in physiotherapy intervention.

A patient-specific phantoms, which are equivalent to human tissues, is needed in the experimental dosimetric verification before radiotherapy treatments. Most of the shape of gel phantoms have been structurally limited because of the fabrication method using mold technique. The present study focuses on direct freeform fabrication of gel phantom with the customized optical 3D gel printing system. Life-sized gel phantoms were replicated using conventional mold techniques, the 3D printer with two-step sequential free-radical polymerization process and inter cross-linking network gels as 3D printing materials. The gel phantoms are ultraviolet light-sensitive instead of radiation. The ultraviolet sensitivity of the gel phantoms (using mold techniques) with different molar ratios were experimentally evaluated with transmittance measurements, and were theoretically estimated by curve fitting to the observed data. This measurement gave us the insight that more vinyl monomers in the gel phantoms caused rapid polymerization and visibly opaque as well as conventional gel dosimeters. We confirmed that inter cross-linking network gel was 3D printable with the customized 3D printer, with resolution of fabrication 500 μm, as pre-finger-shaped phantom. The cross section of 3D printed gel phantom showed the distribution of opacity, that is, the distribution of UV irradiation. We expect that the 3D printer specialized gel materials and ICN gels are feasible for practical fabrication method of 3D gel phantom.

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.

Recently, 3D printers are being used in Medical field. We had developed 3D Gel Printer known as SWIM-ER. However, it is capable of only printing monochrome gels. In this work we present development of a new 3D printer which is capable of 3D printing pigment based color gels. In order to develop this new full color 3D Gel Printer we selected three pigments: cyan, magenta and yellow. We made gel palettes to find target color of gel easily. We found that by mixing three different colors we can obtain wide color spectrum for our Full Color 3D Gel Printer. However, it was also found that wet can not obtain black and white color gels. Therefore, there is a need to select black and white pigment. We will develop color gel database by which a recipe for the target color can be obtained.

Crosslinkers play essential role in determining physical properties of gels. Using cray substance, Laponite (Rockwood Additive Ltd, USA), as the crosslinker, we made N-isopropylacrylamide(NIPA) gels. We found, if we count one Laponite crystal as one crosslinker, that NIPA gels crosslinked with Laponite gelled at much lower fraction (1/2000) of crosslinker than the gel crosslinked with popular N,N'-methylenebisacrylamide(BIS). This result indicates that Laponite is extremely multifunctional crosslinker. Though the volume changes of the NIPA-Laponite gels were continuous one, the volume change itself was much larger than that of the NIPA-Bis gels, and we observed the hysteresis loop as well as the miner loops just like magnetic system. We will discuss about the possible mechanism of such hysteresis loops.

Recently high-strength and high-functional gels have been developed and are expected to be used in industrial and the medical fields. However, the research of gel application has not made much progress from the reason why an environmental range to use being small and properties of matter evaluation are not performed enough. To control the surface friction of gel mechanical materials by the electric field, here we study the effect of the applied voltage on the frictional properties of double-network gel (DN gel) with high strength. We found that impressed voltage on the gel has an ability to control the frictional force of the hydrogel. The results of the tensile and compression tests showed that the behavior of the DN gel was similar to a rubber, and effective data as mechanical materials were obtained. The results of friction measurement using reciprocating friction tester showed that the coefficients of friction depend on the sliding velocities. In the case of the cathode measurement ball, the coefficients of friction decreased with increase in voltage in the range of 0.0–3.0 V and increased with increase in the applied voltage in the range of 3.0–5.0 V. In the case of the anode measurement ball, the coefficient of friction increased with increase in the voltage. The current value measurement was performed in a measurement ball and a stainless-steel plate, and the electric current flowed at approximately 2.5 V and above. It is considered that the applied voltage controls the thickness of water lubricant layer and change the coefficient of friction of the gel. These findings provide a new insight into our understandings of application of the high-performance gels device as well as the development of high-performance gel materials.

Hydrogels are known as a soft and water-rich material, and they are widely applied in the medical and industrial fields. On the other hand, when a liquid material is poured into a mold to make a gel, it is generally difficult to form a complicated shape due to the shape restriction included in the mold. To overcome this challenge, we have independently developed the 3D gel printer "SWIM-ER". This gel printing can make very complex structures that is unable to create by the hydrogel molding process. The our previous works includes soft robots for teaching, research, and surgical simulation and applications of 3D-printed organ models in hydrogel. However, it should be pointed out that due to the high economic cost, this printer is not popular. This study proposes an inexpensive gel printing technology using a commercially available stereolithography 3D printer equipped with liquid crystal display (LCD) or digital light processing (DLP) technology for UV irradiation. The price of a commercial 3D printer for general use ($500) is much cheaper than the price of a 3D gel printer. We have confirmed that our proposed method can perform three-dimensional modeling of gel by photopolymerization reaction under excitation of 405 nm. Figure 1

Soft hydrogel, which contains a amount of water and also has a unique touch feeling, will be required for practical applications around soft-matter robotics including the medical field because it has an unique softness that is close to the living body and has a biocompatibility. Among them, our SWEL developed RepRap SWIM-ER, a desktop type 3D gel printer that enables 3D free-formation of soft hydrogels. The RepRap SWIM-ER is a device that can shape the soft hydrogels into a desired shape by moving a laser pointer as the light source and irradiating the gel solution in the bathtub with ultraviolet light for photo-induced gelation. This 3D gel printer can be realized at low cost because it utilizes the results of the RepRap open source project to design the device and control it with software. Furukawa established the “Soft 3D Co-creation Consortium” (URL: https://soft3d-c.jp) in April 2018. Considering the members of this consortium as test users, we will provide a desktop type 3D gel printer RepRap SWIM-ER. First, in the field of research and development, we will use the 3D printing of soft hydrogel materials and share the practical use cases among the consortium members At the same time, we are planning to standardize the several methods concerning both the material design of 3D gel printers and the evaluation of shaped objects. Figure 1

Polymer gels containing a large amount of water have biocompatibility and appropriate softness close to living biological tissue. For this reason, many studies focus on how to use the polymer gels in medical field. The generally organ model is made of a silicone resin and is transparent and hard. Therefore, excellent in confirming the position of blood vessels and the like. But it is not suitable for practice or simulation using medical device. So, we aim to develop the gel organ model that overcomes these problems. We developed the desktop type 3D gel printer “RepRap SWIM-ER” which enables three-dimensional(3D) free printing of gels. RepRap SWIM-ER can move a light source at 405nm and form gels in the desired shape by localized photopolymerization. This gel printer irradiates a gel solution layer by layer with UV light. In the conventional printing process of RepRap SWIMER, it was difficult to change the photo polymerization reaction locally because constant speed, scan time and so on. There was also problem that it could use only one gel solution because it was bathtub type 3D gel printer. Here, we developed new printing process of RepRap SWIMER that can change the transparency and mechanical properties of printed gels locally by changing the printing parameters such as the scan times of UV light. It can control gel turbidity which was previously only printed in a single color. This method can print two types of gel (transparent and white) only using RepRap SWIM-ER. By changing the printing conditions with RepRap SWIM-ER, a transparent gel with length and breadth of 20 mm, thickness of 2 mm and a white gel lattice can be printed at about 10 minutes. The transmittances of printed transparent gels and white gels were measured by a spectrophotometer to examine the color change (Figure 1). It can be seen from Fig.1, The white turbidity of the gel changes when the printing conditions are changed. This result showed that the appearance of color varied depending on the concentration of the hydrophobic initiator TPO used in the gel solution. At the prototype, we tried to print using kidney data. From previous research, we have known that the gel prepared by soaking in pure water swells 1.5 to 2.0 times. In consideration of this result, when printing kidney data using RepRap SWIM-ER, it was printed at 70% of the size of the data, the color was entirely white. After swelling, this model became to be about the same size as the actual data. The kidney 70% data can be printed at 2h30min. We can create new gel organ models by using RepRap SWIM-ER and the above gel printing method. Gel organ models makes it possible to use medical devices and makes the touch feeling more realistic. For example, soft-transparent gel (organ model) and hard-white gel (blood vessel, tumor) can make the model with high precision and complexity. In addition, this technology can let the production spend lower cost and less time. Figure 1

Hydrogels are three-dimensional polymeric networks capable of absorbing large amounts of water or biological fluids. Due to their high water content, porosity and low friction they closely simulate natural living tissue. The properties of a polymer gel depend on the chemical structures of the component molecule and can be controlled or tuned by external stimuli such as heat, optics, solvent, and pH. Shape-memory gels (SMGs) are unique materials that have the ability to return from a temporary deformed state to their permanent i.e. original shape induced by an external stimulus like temperature change. Poly(dimethyl acrylamide-co-stearyl acrylate) (DMMA-co-SA)-based SMGs show such behavior with high mechanical strength, transparency and moderate water content (≈30wt%). In this work, we applied stereolithography process to fabricate DMMA-co-SA SMGs and printed sample models like gel sheets and tubes. However, printing a transparent SMG was not an easy task due to several problems like sample turbidity, swelling during printing and shape deformation. We critically maintained these uses and compared the properties of 3D printed SMGs with that of conventionally synthesized SMGs. Finally, we analyzed the limitation and potential of 3D printing process and discussed a suitable approach for application of 3D printed SMGs as an actuator.

Gels, soft and wet materials, have unique properties such as transparency, biocompatibility, and low friction. In recent years, high strength gel has been developed. Various studies take advantage of these characteristics has proceeded, we research to use high strength gel. High-strength gels are expected to be put to practical use in various situations. For example, gel organ models and gel artificial blood vessels are required at a medical site. Also in the field of robotics, soft materials are drawing attention. To put a high-strength gel into practical use, it is necessary to free-form a gel using a 3D gel printer. We developed a 3D gel Printer "SWIM-ER", has enabled modeling of complex shapes of the gel. However, this is expensive. Therefore not all of the gel researchers and the companies have such a device. “RepRap” is the abbreviation for “Replicating rapidly prototyper”, the open source 3D printer. Most of the RepRap parts are made of a resin, and the 3D digital data of the parts and its firmware are posted on the internet. Therefore, we can easily create another 3D printer by building the parts with a 3D printer and programing the firmware on an inexpensive electronic substrate like the “Arduino”. In this research, we aimed to develop a low-cost 3D gel printer which can be used by anyone.

The aim of developing a multi-material 3D printer is to print an object with a different kind of soft and hard material in a single run. It is expected that the combination of printing soft and hard material will be a new kind of 3D printer. The main printing material for this printer is the conductive based soft filament made by our laboratory “Soft & Wet Matter Engineering Laboratory”, along with other different soft filament and hard plastic filament to create a fully functional, multi-material printer to print objects in a single printing run with greater diversity and lower cost than any other single material printer. The biggest challenge for making this printer is to develop a soft material’s extruder because in 3D printer most of the materials are used is hard filament. So, to overcome this we are developing a special type of screw-based Extruder, where a huge range of polymer material can be processed in an application of 3D printer objects. This type of extruder is not so common in 3D printing field. Instead of the filament, we will use the conductive material as pellet or powder for this screw-based extruder. It is assumed that this type of screw-based extruder can solve the problem of combination of printing soft and hard material in a single run. Such type of screw base extruder will be a new era of the 3D printer and it could be a good STEM tool in Sensor and Robotics. Moreover, it is expected that it will be a new addition to the additive manufacturing process.

In order to construct the artificial cells and to understand the physicochemical properties of living cells, it is important to clarify the cell-sized confinement effect on the behaviours of bio-inspired polymers. We report the dynamic behaviours of aqueous hydroxypropyl cellulose (HPC) solution coated with phospholipids in oil (water-in-oil droplets, W/O droplets), accompanied by an increase in the temperature. We directly observed the beginning of phase separation of HPC solution using a fluorescence microscope and confirmed the dependence of such phenomena on droplet size. The results indicate that the start time of phase separation is decreased with an increase in droplet size. The experimental results suggest that the confinement situation accelerates the phase separation of aqueous HPC solutions.

In this study, we evaluated the mechanical properties of printed structures with respect to the printing orientation for "SWIM-ER". The fracture surface of the 3D modeled object of the gel does not break along the stacked line, and the maximum stress at that time is the breaking strength. Moreover, the dependency in the stacking direction is weak in the 3D model of the gel. The gel printed at high speed scan showed lower elastic modulus and higher moisture content than gel printed at low speed scan. We discussed about crosslinking density calculated based on the compressive elastic modulus and moisture content, respectively. It was found that gels having different crosslinking density can be formed by the scanning speed of UV laser. In addition, we made a prototype of a gel finger model with different mechanical properties within the model.

Additive manufacturing or 3D printer is one of the most innovative material processing methods. We are considering that human resources for 3D printing would be needed in the future. To educate the abilities of the digital fabrication, we have the public digital fabrication space “Eki-Fab” for junior and high school students and Project Based Learning (PBL) class for undergraduate students. Eki-Fab is held on every Saturday at the Yonezawa train station. In the “Eki-Fab”, anybody can study the utilizing of 3D printer and modeling technics under the instruction of staff in Yamagata University. In the PBL class, we have the class every Thursday. The students get the techniques of the digital fabrication through the PBL.

Gels are soft and wet materials having low friction, good biocompatibility, and material permeability. It is expected that gel materials will be used as new kinds of industrial materials in the engineering and medical applications. But it cannot build a complicated shape. Soft & Wet Matter Engineering Laboratory developed a 3D gel Printer "SWIM-ER", has enabled modeling of complex shapes of the gel. However, this is expensive. Therefore not all of the gel researchers and the companies have such a device. To solve this problem, we manufacture a low-cost open-source 3D gel printer "RepRap SWIM-ER" from the RepRap. We made the components required to manufacture the “RepRap SWIM-ER” from the 3D printer and chose a light source. In addition, we produced the P-DN gel for RepRap SWIM-ER and conducted the molding test to confirm whether RepRap SWIM-ER can used it.

United Nations set the goal to maintain the richness of the sea in SDGs. In Japan, they are aiming for broad spectrum and real time of ocean information collection. Various kinds of underwater exploration techniques have been developed. For instance, 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 non-biodegradable materials such as metals. For this problem, we came up with the robot composed by only organic material. This idea realizes the recycling society. 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 using a hydrogel. For designing a Jellyfish-mimic AUV robot, it is preferable to introduce a soft actuator driven by water pressure, as it requires low electric power and it is eco-friendly. Here, we report a 3D printing hydrogel hydraulically-driven soft actuator that can make a bending motion of umbrella-shaped bell of artificial Jellyfish. We utilized the Pneunets Bending Actuator for designing the actuator, and the detailed information of this actuator is shown in the website of Soft Robotics Toolkit (see https://softroboticstoolkit.com/book/pneunets-bending-actuator). We changed the parameters of 3D print speed and UV light power gel concentration when we make some gel actuators. In addition, we measured and evaluated these performances. Finally, we are making the robot to use it and be composed by only organic materials so that we can release many robots at the same time.

The 3D Gel Printer Soft and Wet Industrial Materials・Easy Realizer (SWIM-ER) developed by Furukawa et al. It can only perform modeling with monochrome. Therefore, it is thought that new elements will be born by developing a new 3D Gel Printer. However, there are many problems in developing it. In this study, we aim to develop a system that displays the composition of gels for obtaining color gels of target color, and apply it to gel printer. The color gels used pigments, and mixing them showed the change of color of the gels. Moreover, by mixing the pigments, gels with a wide range of color variations could be obtained.In the future, we will study the improvement of accuracy by collecting more samples and the technology to actually color the gels.

Based on the world-first 3D gel printing technology, we aim to develop 3D gel printing system to realize free-shape design of soft and wet materials. We defined ‘Designable Gels’ as revolutionary gels whose molecular structure, shape, and functions can be designed by users. By virtue of the 3D gel printing system, we can use 3D high-performance gels materials and realize both designed 3D shape and designed properties. At the same time, analysis technology with scanning microscopic light scattering will be immediately used to guarantee the quality of manufactured gels. We believe we will contribute to extend the fields of medical and robot applications and create new markets.

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.

A 3D printer is a device which can directly produce objects whose shape is the same as the original 3D digital data. Hydrogels have unique properties such as high water content, low frictional properties, biocompatibility, material permeability and high transparency, which are rare in hard and dry materials. These superior characteristics of gels promise useful medical applications. We have been working on the development of a 3D gel printer, SWIM-ER (Soft and Wet Industrial – Easy Realizer), which can make models of organs and artificial blood vessels with gel material. However, 3D printing has a problem: the mechanical properties of the printed object vary depending on printing conditions, and this matter was investigated with SWIM-ER. In the past, we found that mechanical properties of 3D gel objects depend on the deposition orientation in SWIM-ER. In this study, gels were printed with different laser scanning speeds. The mechanical properties of these gels were investigated by compression tests, water content measurements and SMILS (Scanning Microscopic Light Scattering).

In recent years, the fabrication of patient organ replicas using 3D printers has been attracting a great deal of attention in medical fields. However, the cost of these organ replicas is very high as it is necessary to employ very expensive 3D printers and printing materials. Here we present a new gel organ replica, of human kidney, fabricated with a conventional molding technique, using a particle-double network hydrogel (P-DN gel). The replica is transparent and has the feel of a real kidney. It is expected that gel organ replicas produced this way will be a useful tool for the education of trainee surgeons and clinical ultrasonography technologists. In addition to developing a gel organ replica, the internal structure of the P-DN gel used is also discussed. Because the P-DN gel has a complex structure comprised of two different types of network, it has not been possible to investigate them internally in detail. Gels have an inhomogeneous network structure. If it is able to get a more uniform structure, it is considered that this would lead to higher strength in the gel. In the present study we investigate the structure of P-DN gel, using the gel organ replica. We investigated the internal structure of P-DN gel using Scanning Microscopic Light Scattering (SMILS), a non-contacting and non-destructive.

This pilot study aimed to refine a treatment approach for traumatic grief due to violent loss. Our Traumatic Grief Treatment Program, a modification of Shear's complicated grief treatment (Shear et al., 2005), comprises psychoeducation, in vivo exposure, imaginal exposure, discussion of memories about and imaginal conversation with the deceased. Thirteen of 15 Japanese women suffering from posttraumatic stress disorder (PTSD) due to traumatic grief completed 12 to 16 weekly individual sessions based on their therapists' recommendations. Assessment scales included the Inventory of Complicated Grief, the Impact of Event Scale-Revised, and the Center for Epidemiologic Studies Depression Scale. There was significant reduction in symptom severity at treatment end, and symptom levels remained low throughout the 12-month follow-up period. Based on Jacobson's Reliable Change Index, 46% showed change on all 3 measures. These findings suggest that our treatment model may be feasible for treating traumatic grief with PTSD in non-Western settings.

The authors examined the efficacy of Prolonged Exposure (PE) therapy in Japanese patients with posttraumatic stress disorder (PTSD). Twenty-four patients (21 women, 3 men) with PTSD due to mixed trauma were randomly assigned to the PE group (PE with or without treatment as usual [TAU]) or the control group (TAU) only. The control group received PE after a 10-week period. Intention-to-treat analysis showed the PE group achieved significantly greater reduction than the control group at posttreatment in either PTSD or depressive symptoms. The control group had significantly decreased symptom severity after PE treatment. Symptom levels of 19 PE completers in the both groups remained low in 12-month follow-up assessments. The study's findings will promote the future dissemination and implementation of evidence-based treatment for PTSD in non-Western settings.

3D printing technology has been becoming more common and diverse for various researches and developments. Here we focus on 3D printing of soft-matter, especially introducing the latest progress of our 3D gel printing. We are developing various 3D gel printers, including bath-tub type, dispenser type and brick-building type. These printers can 3d-print finger tips for robotics, medical models for surgery, and fun foods for playing and nursing. The minimum and maximum dimensions of 3D printed objects depend on both the type and the materials used in printing. We will discuss what we need to study for leading Soft-matter 3D Innovation.

Various kind of gel materials for example tough double network hydrogels [1], shape memory hydrogels [2] and ionic gels [3] have been developed with potential in numerous sectors. The transparent, flexible and low friction properties of these gels have added different prospects in scientific and technological areas. Utilization of 3D printing in fabrication of gel materials is still in its infancy and thus hindering rapid prototyping and design freedom. In this work, we have fabricated smart gels like thermos-responsive gels and conductive gels etc. using both customized optical gel 3D printers named SWIM-ER and commercial printer named Acculas. This process of 3D printing enabled rapid and moldless fabrication of smart gels with variety of 3D design from macro to micro scale. Robust thermos-responsive Poly (dimethyl acrylamide-co-stearyl acrylate and/or Lauryl Acrylate) (PDMMAm-co-SA and/or LA)-based shape memory gels (SMGs) with tunable mechanical, thermal, swelling, and optical properties are obtained by optimizing their critical conditions during 3d printing. The superior physiochemical properties of such smart gels widen the range of applications for soft robotics, biomedicine, flexible electronics, mimicking organ structure, bioinspired lens and sensing applications. References Gong, J. P., Katsuyama, Y., Kurokawa, T., Osada, Y., “Double-Network Hydrogels with Extremely High Mechanical Strength,” Adv. Mater., 15, 1155-1158 (2003). Kabir, M.H., Ahmed, K. Furukawa, H., Microelectron. Eng. 150, 43–46 (2016). Ahmed, K., Watanabe, Y., Higashihara, T. Arafune, H. Kamijo, T., Morinaga, T. Sato, T., Makino, M. Kawakami, M., Furukawa, H. Microsyst Technol 22, 17 (2016).

Today, intravascular catheter surgeries, which are kind of minimally invasive procedures, are widely used surgical techniques. As compared to conventional open surgery, incision size is small, and burden on patients is reduce. Therefore, the wounds associated with pain is small, and time to heal is also short. On the other hand, since operative field was restricted during surgery, operators need to have sufficient skill for intravascular catheter surgeries. To obtain it, operators must practice using artificial surgical simulators. Materials for surgical simulators are requires having physical properties as like human organs. Although lab animals have similar physical properties, they are not appropriate from an ethical perspective. Moreover, recently, silicone-based materials are used for surgical simulators, but their physical properties do not mimic those of human organs. Gel materials are expected for materials of surgical simulators, because their mechanical properties are similar to human organs and they contain large amounts of moisture. Besides, gel material can apply for fabrication of the complicate shape of human organs using 3D printer. The issue of practice using conventional surgical simulators is quantitative evaluation of operator skill. In the case of intravascular catheter surgeries, measurement of applied force to vessel wall by catheter and guide wire is an important function. Since vessel walls of patients are delicate, if devices applied excess force, and unexpected accidents such as vascular occlusion are attracted. In this study, we focused on the photoelasticity of gel materials. If vessel models are made of these gel materials, it is possible them to evaluate quantitative score of operator skill. To realize these surgical simulators, we developed the stress measurement system for photoelasticity of gel materials. Besides, we evaluated the physical properties such as mechanical properties and photoelastic coefficient of several gel materials using our developed system. We constructed new stress measurement system for photoelasticity of gel materials Our system consisted of several polarizers and wave plates, and it could measure the value of stress and direction of stress in X-Y plane from RGB values on color map. In order to minimize the overlap ratio of the same color in the color map, two 1 wave plates were insert to conventional observation system of circularly polarized wave and the insertion angle of two 1 wave plates is 30 degrees. We suggested analysis algorithm which enables to eliminate the effects of incident light and ambient light. As the results, we succeed to measure the tensile stress by our system during the tensile test of PVA hydrogel. Measurement error was less than 6.3% at the stress range from 0 to 80 kPa, and it is sufficient measurement resolution for evaluate stress during practice of intravascular catheter surgeries. Generally, Young’s moduli of human vessels depend on the organ and/or symptoms, and they are ranged from 0.02 to 3 MPa. Although mechanical properties of gel material can be adjusted by changing kinds of formulas and their concentrations, it is difficult that only one type gel coverall the range of Young’s moduli of human vessels. Therefore, the materials of surgical simulators are selected on demand from patient of case history. Finally, we investigated the Young’s moduli and photoelastic coefficients of two types of designable gels such as inter cross-linking network gels and double networks gels. As the results, two type gels exhibited photoelasticity. Young’s moduli of inter cross-linking network gels are approximately 1 MPa and the effect of formula concentration was slightly. On the other hand, the range of Young’s modulus of double networks gels was 0.12 to 0.77 MPa for strain range from 0 to 15%, and it was within the range of Young’s modulus of human vessels. Their photoelastic coefficients were 0.012 to 0.022 ×10-9 Pa-1. The measurement error of our system was 7.3%, and was acceptable.

In recent years, various high-strength gels having strength of several MPa have been developed one after another by devising the internal structure of the gel. They have attracted attention as a new material. High-strength double network gel (DN gel) is a gel consisting of a hard 1st network and a soft 2nd network and have excellent properties such as super low friction, flexibility and biocompatibility. Particle double network gel (P-DN gel) consisting of powdered 1st network and 2nd network is a high strength gel capable of 3D free form fabrication by using 3D gel printer. Utilizing these advantages, there are expectations for soft robot materials and mechanical materials. It is also important to grasp the number of deformation of the gel and how much fatigued it is when the gel material is industrially used. Specifically, by attaching a fatigue sensor to a soft robot, it is possible to predict the optimum time to replace the parts. When it is used for mechanical materials, we need to judge on the necessity of emergency treatment. It will be considered to lead to comfortable use of things. In this study, we aimed to develop a gel fatigue sensor with reference to the internal structure and destruction phenomenon of P-DN gel. P-DN gels of various compositions were prepared and mechanical tests and evaluation of internal structure by dynamic light scattering were carried out to investigate the physical properties of these gels. As a result, the P-DN gel using super absorbent polymer (SAP) as the 1st gel showed the most suitable physical properties for use as a fatigue sensor.

Various kinds of cell model systems have been utilized for fundamental studies on physical properties of cells. Water-in-Oil (W/O) droplet system coated with phospholipids is one of the beneficial simple model systems of living cells. For instance, a biomimetic phase-separated membrane was constructed in the W/O systems with phospholipid mixture (Hamada et al., J. Phys. Chem. Lett., 2010) since phase separation in lipid membrane system corresponds to the separation between lipid raft domains and other soft domains in the living cell membranes. Phase transition of a polymer has been studied for many years, such as coil-globule transition (Nishio et al., Nature, 1979), and helix-coil transition (Tanaka et al., J. Chem. Phys., 1973). In addition to the phase transition of polymers, phase separation in a binary polymer solution was also reported (Yanagisawa et al., J. Mol. Liq., 2014). However, cell-sized confinement effects on polymer solutions have been poorly confirmed. To clarify the cell-sized confinement effects on polymer solutions, we previously observed the dynamic behavior of polymer droplets (Yoshida et al., Polymers, 2017). The previous study revealed that droplet size influences the start time of phase separation in the case of temperature change from 10 to 65 degrees Celsius. In this study, we observed the dynamic behavior of hydroxypropyl cellulose (HPC) solution droplets in response to temperature change from 10 to 65 degrees Celsius using a fluorescence microscope. The droplets were coated with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE). As a control, we observed non-coated water droplets. DPPC and DPPE are widely used for studies on model cell membranes. Using time-lapse images, we confirmed the water/HPC distribution using a spatial autocorrelation function. The results revealed that water-rich region appeared in the case of lipid coated droplets with increase in temperature while such phenomenon was not observed in the case of non-coated droplets.

Since the gel has soft physical properties, it was difficult to process by conventional cutting or casting, but 3D gel printer was developed, and three-dimensional free modeling of the gel became possible. In this study, it is presented that the relationship between printing parameters of a 3D gel printer "Soft and Wet Intelligent Matter-Easy Realizer (SWIM-ER)" and mechanical properties of the fabricated gel objects by SWIM-ER. The printer can fabricate hydrogel objects by scanning of ultra-violet (UV) light irradiation (photopolymerization). Various hydrogels objects were printed with different scanning velocity of UV light. We measured the water content and mesh sizes of gel objects utilizing Scanning Microscopic Light Scattering (SMILS). Furthermore, we also printed the gel objects with multiple scan rates with constant UV light irradiation energy, and measured sizes of gel objects, and performed the compression test. It was observed that the physical properties of printed hydrogel objects are strongly related with 3D printing parameters due to difference in crosslinking density of polymer network.[1] Ref. [1] Takafumi Ota, et al., Mechanical Engineering Journal, 5, 1, 17-00538 (2018).

Catheterization procedure is a typical example of minimally invasive medical treatment. This has the advantage that the physical burden on the patient can be remarkably reduced as compared with the conventional medical treatment method involving craniotomy or hemorrhage etc. However, on the other hand, since visual and tactile restrictions are limited at the time of surgery, physicians are required to have expert skill and many experiences. To raise the success rate of surgery irrespective of the amount of surgical experience, we have conducted a simple model using a glass tube and a simulation operation using an experimental animal, but they have low bio-reproducibility and ethical problems was there. In recent years, due to the development of new materials and the appearance of 3D printers, shape reproducibility has improved. A more desirable function of the surgical simulator is to visualize the force applied to the vessel wall surface by the catheter. This is because there is a danger of attracting vascular occlusion etc. when a large force is applied to the wall surface of the blood vessel. Therefore, it is considered important to quantitatively evaluate the operational feeling for simulated surgery. Therefore, we aim to manufacture a vascular surgical simulator with high bio-reproducibility that enables real-time stress measurement. In this research, stress visualization method using photoelastic effect is applied to surgical simulator. By using the photoelastic effect, it becomes possible to check the stress state of the entire field of view, and it is possible to obtain a stress state when a medical instrument such as a coil or a stent is inserted. Therefore, it is useful not only for training but also for the development of medical instruments. Heretofore, examples using PDMS and polyurethane elastomer as a surgical simulator material have been reported, but the longitudinal modulus of elasticity is high and it is unsuitable for a blood vessel model. Therefore, we focused on PVA hydrogel as surgical simulator material. PVA (polyvinyl alcohol) hydrogel is a material that can be expected to reproduce vascular tissue because its physical properties can be easily changed by changing the compounding ratio and degree of polymerization of powdered PVA. By changing the compounding ratio of powdered PVA in the range of 4-15 wt.%, We realized PVA hydrogel's longitudinal elastic modulus of 60-450 kPa. Since the longitudinal elastic modulus of human vascular tissue is 20-3000 kPa, PVA hydrogel is useful for reproducing soft vascular tissue. Further, the average photoelastic coefficient of PVA hydrogel is 2.30 × 10-9 Pa-1, which has a photoelastic coefficient greater than that of polyurethane elastomer which is a photoelastic material useful for photoelastic stress measurement. (photoelastic coefficient of polyurethane elastomer is 1.45 × 10-9 Pa-1.) Therefore, it was confirmed that it is a useful material for stress measurement using photoelastic effect. In this study, a simple blood vessel model was prepared using PVA hydrogel and simulated surgery using a catheter was performed. In addition, a photoelastic observation system was constructed for stress measurement, and a method for correcting the influence due to the presence of incident light, ambient light, and initial stress was examined. As a result, we successfully extracted and visualized the stress applied to the simple blood vessel model.

Various kinds of underwater exploration techniques have been developed. For instance, 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 non-biodegradable 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 using a hydrogel. For designing a Jellyfish-mimic AUV robot, it is preferable to introduce a soft actuator driven by water pressure, as it requires low electric power and it is eco-friendly. In this study, we prototyped a Jellyfish-AUV robot using a soft material and a soft actuator. While it is ideal to make a robot body with hydrogel it is difficult to make the actuator with hydrogel. Here, we report a silicone-based hydraulically-driven soft actuator that can make a bending motion of umbrella-shaped bell of artificial Jellyfish. We utilized the Pneunets Bending Actuator for designing the actuator, and the detailed information of this actuator is shown in the website of Soft Robotics Toolkit (see https://softroboticstoolkit.com/book/pneunets-bending-actuator). The actuator is composed of inflation parts, basis, and copy paper placed between them. We poured into the 3D printed mold made with polylactic acid (PLA) and preserved at room temperature for 4 h to cure the silicone parts (inflation parts and basis). Copy paper was sandwiched between inflation parts and basis. The size of copy paper was 30 mm × 5 mm. Then, we poured additional silicone resin to combine the parts. By inserting a toothpick into the mold, we made the insertion port of the silicon tube. Before curing, we removed the air bubbles for 20 minutes with a vacuum de-foaming device. Finally, we inserted a silicon tube into the fuselage and attached a syringe for air supply. 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. The results were obtained as shown in Figs.1, 2 and 3. The shrinkage ratio of the jellyfish robot was 46.4 % at the maximum in the case of air injection of 2.8 cm³. The ratio did not reach 56.3 % at the maximum shrinkage ratio of the real jellyfish. To achieve the 56.3 % shrinkage ratio, we have to improve the maximum volume of injection air. Consequently, we have concluded there is a possibility that this actuator can reproduce jellyfish movement.

The purpose of this study is to evaluate effect of hypoxic water and blue tide on macrobenthos in artificial tidal flat, Omaehama in inner part of Osaka bay. Hypoxic water influences on macrobenthos to survive under to 1m water depth. In addition, it was revealed that bule tide influences on the amount of filtered water by Ruditapes philippinarum in DL±0m water depth. Blue tide decreased individual of R. philippinarum and the amount of filtered water by them. It is found that the creating artificial tidal flat enhances the number of R. philippinarum and filtaration, but occurrence of blue tide causes disappearance of purification function. These result indicated that it is necessary to consider the method for mitigation of blue tide impact when creating artificial tidal flat.