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In recent years, there has been a growing demand for safe soft robots that work in a work environment similar to that of humans. The use of 3D modeling technology in the manufacturing of soft robot chassis, soft electronic parts, and wiring processes is expected to lead to more efficient and smaller soft robot manufacturing. The objective of this study is to fabricate a gel capacitor using ionic liquid as an electrolyte, which has characteristics such as non-volatility, flame retardance, and conductivity. We fabricate ionic liquid gels that possess flexibility and conductivity after curing using a photoformable 3D gel printer, and discuss their performance as capacitors.

Automation in the food services industry is not as developed as in the automotive and electrical industries. This may be because (1) the tasks involve high-speed operations in unstructured environments and (2) the lack of effective robotic end-effectors. In this letter, we focus on the automation of dishwashing operations and propose a robotic hand capable of withdrawing and grasping a dish plate from a pile, even when there is water or oil left on the plate in a post-meal scenario. The robotic hand consists of withdrawing and grasping mechanisms. Each mechanism is actuated by two bellows actuators. Soft pads with special groove patterns were fabricated and used to provide sufficient friction when they come into contact with the plate. A theoretical analysis of the withdrawing and grasping operations was performed, and an analytical model of the bellows actuator was established by considering both the pressure thrust force and the elastic force. Bellows actuators were designed based on the analysis and fabricated using both 3D printing and casting methods. Characterization of bellows actuator was performed to validate the analytical model, and agreement was found on the thrust force, but discrepancy occurred in the elastic force due to the complex structure and deformation mode of bellows. Finally, handling experiments on different plates were conducted and results demonstrated that the proposed robotic hand can successfully withdraw and grasp a plate from a pile.

Dynamic X-ray elastography using propagating shear waves is a novel technique to visualize the spatial distribution of elasticity in soft materials. We demonstrate that it can be applied to a gel sample with a fine structure. We prepared a viscoelastic gel sample with a two-dimensional lattice structure filled with ZrO2 particles, and applied the technique to map storage and loss moduli. The obtained storage modulus map successfully distinguished the harder lattice structure from the soft gel matrix with a spatial resolution much higher than those of other conventional elastography techniques using magnetic resonance and ultrasound.

The research of soft robots composed of soft materials, named "Soft-matter Robotics", has been drawn attention because it is useful as a technology with high interpersonal affinity. The soft-matter robots have a potential advantage in non-destructive behaviors such as picking up an egg without breaking it. On the other hand, IoT / AI technologies such as smart speakers have become popular in the past several years from the viewpoint of software functions of robots. Robots equipped with communication functions based on IoT technology are also gradually permeating our lives. In the situation where the robot directly touches the human, the soft-matter robot fused with the IoT technology will have the flexibility of the body and the IoT sensor module, so that it is possible to achieve the advanced interaction without damaging the human. However, the softness of the soft-matter robot depends on its material characteristics. It is necessary for realizing the advanced communication to clarify the property of the sensing data of physical contact with human that the installed IoT module can acquire from the material. This study verifies whether the touching method such as poking, stroking and so on of a three-dimensional object of additive type silicone rubber can be classified through a vibration sensor. Then, we develope a robot that communicates with humans by feeding back the sensed data with light and vibration. Figure 1

A liposome is a spherical particle formed by a surfactant bilayer. This particle uses in drug delivery systems, in cosmetics as a model of cell membranes and it often studies in biology and medical science. Furthermore, new materials including polymer-reinforced liposomes have the potential to be applied as mechanical materials for soft equipment in soft robots from the viewpoint of texture expression. On the other hand, there is a problem that the liposome is not suitable as a mechanical material because the liposome is soft and fragile.This study uses liposomes with gel materials such as gelatin and shape memory gel (SMG) to enhance their resistance to mechanical stress. We show the encapsulation procedure gelatin and pre-gel solutions for SMG in liposomes by using the Droplet-Shooting method. This procedure allows the encapsulation of liposomes by gel. Some droplets are shot from the tip of capillary, through the oil-water interface and become liposomes. First, we incorporate gelatin into liposomes, however the gelatin solution has higher viscosity than water. Therefore, this process should be confirmed the effect of the viscosity of gelatin on liposomes generated by the Droplet-Shooting Method. In the case of SMG, we can observe the effect of the UV irradiation on the liposome containing the pre-gel solutions because the irradiation of UV makes the lipid membrane unstable and then breaks liposomes. This study discuss stable formation of polymer-reinforced liposome. We believe that our procedure will contribute to the making novelty materials. Figure 1

We want to develop a soft-matter Mono pump for infant Ventricular Assist Device (VAD). In this research, we have developed the Mono pump, which is made of soft materials and hard materials to study the effect of applying the soft materials to the Mono pump. The stator of the 3D printed Mono pump was made with biocompatible soft materials called Inter Cross-linking Network (ICN) gels. We believe that ICN gels have not only specific toughness and low friction but also excellent biocompatibility that can prevent blood cell trauma and the transplant rejection. Moreover, the rotor is made of hard materials using commercial resin or filament based 3D printers, (Form 2 and Flashforge Creator). Finally, we will compare the practical and theoretical displacement from the flow rate measurement to implement the best performance of the Mono pump in practical use. Figure 1

Functional and intelligent soft materials are useful for controlled release of medicines and other molecules. Poly(N-isopropylacrylamide) (PNIPAm) gels are well known as thermo-responsive gels with large discontinuous volume change which is commonly called as the volume phase transition. PNIPAm gels are expected to be applied to controlled-releasable material for drug delivery systems. Furthermore, we can fabricate arbitrary shapes made of gels freely by using 3D hydrogel printing techniques. Here we report that the effect of capsule shapes on behaviors of the PNIPAm objects under water flow with Reynolds number 102. In addition, we compared the behaviors of 3D-printed PNIPAm gel objects with 3D-printed polylactic acid (PLA) objects. The velocity at the first period of 2 or 3 s from the beginning of movement is slower than that of second period in the case of PNIPAm objects with ellipsoidal and bullet shapes. In other words, the capsules are accelerated after the period of 2 or 3 s. For the bullet shape objects, the velocity of the PNIPAm gel is approximately three times faster than that of PLA. It is considered that the cause of the difference between the velocities of PLA and PNIPAm gel is the difference of their frictions. The hydrogels possess commonly low friction properties. Finally, it is demonstrated that the 3D-printed PNIPAm capsules can release the solution inside the capsules by shrinking the PNIPAm gels, caused by volume phase transition.

A decreasing swallowing function with natural aging may cause a pneumonia. It is important for elderly person to measure a swallowing function to prevent swallowing disorder. To examine the swallowing function in a daily living environment, the swallowing examination device was required to be simple and non-invasive for human body. In this paper, we propose the non-invasive swallowing examination device using a hetero-core fiber optic pressure sensor, which can monitor the movement of the laryngeal prominence (LP) during swallowing by the pressure change to the outside of the skin. As a result of the swallowing test, the proposed fiber optic swallowing test device has been indicated to detect the movement of the LP during swallowing.

Progressive cavity pumps (PCPs) consist of a rotor and a stator. The extrusion process of PCPs is governed by a single-helical rotor which rotates eccentrically within a double-helical stator of twice the pitch length. Between the seal lines (the contact lines of rotor and stator), there are cavities which are constantly moved towards the discharge end of the pump. As one cavity is eliminated, another cavity develops, keeping the cross-sectional area of the cavities constant. The process makes a continuous non-pulsating flow in the PCPs. The developed pushing–and–suction action allows PCPs to exert significantly lower shear rates on the pumped material, compared to other pump types, such as membrane pumps or peristaltic pumps. However, the sliding of the rotor and stator in the pump causes a biting phenomenon [1-3]. Therefore, the degradation of particles in the fluid occurs. In this study, we adopted a flexible, low-friction gels as the stator material. By using gels materials as stator, we could make a pump that could discharge at low torque as previously reported by our group [4]. In this work, the rubber stator and the gels stator fabricated by 3D printing were compared and evaluated by performing discharge and torque test. References: [1] K. Nishimura, E. Uetsuji, and Y. Iwai, “Study on the Behavior of Particles in the Sliding Portion of a Progressive Cavity Pump”, Journal of Japanese Society of Tribologists, Vol. 63 (2018), No. 9 pp. 641-650 [2] P. Fisch, M. Holub, and M. Z. Wong, “Improved accuracy and precision of bioprinting through progressive cavity pump-controlled extrusion”, 2021 Biofabrication 13 015012 [3] M. Horie, S. Shigemitsu, S. Ookura, “Fundamental Study on Pediatric Single Eccentric Screw Blood Pump”, Turbomachinery, vol. 43(2015), No.4 pp.222-228 [4] Yeh, Yee Cheng, Naoya Yamada, Yosuke Watanabe, MD Nahin Islam Shiblee, Jun Ogawa, Ajit Khosla, Masaru Kawakami, Teruaki Akamatsu, and Hidemitsu Furukawa. “3D Printing of Soft-Matter Mono Pump in Infant Ventricular Assist Device (VAD) for Blood Pumping” ECS Transactions 98, no. 13 (2020): 31.

Currently, there are Collaborative robots (cobots) that use multiple robots to solve a single, simple task, such as finding survivors in rubble or monitoring the environment during a disaster. [1] Such robots are moved by vibration motors and communicate with nearby robots via infrared communication for control. In this study, we develop a soft robot that can search for heat sources and solve simple tasks using only a simple structure without any sensors. This soft robot can move by simply vibrating and has a mechanism to switch its motion mode when the temperature of the ground surface or the air changes. The robot is equipped with shape-memory gel [1], which softens and increases the friction rate as the temperature rises, and hardens and decreases the friction rate as the temperature decreases. The shape-memory gel has the property of remaining stationary when the temperature on the ground or in the air rises, and operating when it falls. In our experiments, we measured the absorption of vibration, friction rate, and tackiness in order to verify the effectiveness of controlling the motion of the shape memory gel by temperature. It was confirmed that the vibration was absorbed when the shape memory gel became warm and soft. In the measurement of friction rate and tackiness by temperature, it was confirmed that both friction rate and tackiness increased by increasing the temperature. As a result, the effectiveness of the shape-memory gel was confirmed by temperature. Next, we fabricated a soft robot as shown in Fig. 1 and conducted experiments to see if its motion changed depending on temperature. In the future, we will conduct experiments to see if the soft robot can be used to solve simple tasks such as transporting plants to sunlight. Reference: [1] Michael Rubenstein, Christian Ahler, Radhika Nagpal Kilobot, “A low cost scalable robot system for collective behaviors” 2012 IEEE International Conference on Communications (ICC)https://ieeexplore.ieee.org/document/6224638 [2] Ahmed, Aamir, Sandeep Arya, Vinay Gupta, Hidemitsu Furukawa, and Ajit Khosla. "4D printing: Fundamentals, materials, applications and challenges." Polymer (2021): 123926. https://doi.org/10.1016/j.polymer.2021.123926 Figure 1

4D printing [1] is a new interdisciplinary research area made possible by the merger of scientific developments in additive manufacturing and smart materials [2]. It is a technology that allows 3D printed objects to be deformed over time by applying specific external stimuli [3] and is currently attracting attention as a technology to program biological-like movements into the internal structure of 3D printed objects. In previous research, the movement and deformation of the model has been controlled by devising the shape of the structure, such as a bilayer structure consisting of two materials with different physical properties [4]. However, it is difficult to realize the deformation in different directions simultaneously. The purpose of this research is to develop a 4D printing technology that can simultaneously deform each part of the same object in any direction. To develop a 4D printing technology that can simultaneously deform each part of the same object in any direction, we analyzed the principle of 4D printing by swelling. We measured the swelling rate, swelling speed, compression test, and deformation amount in order to investigate the effects of material and laser irradiation frequency. As a result, it was confirmed that the swelling rate and swelling velocity increased when the amount of the initiator, TPO, was increased from a specific laser irradiation frequency. It was also confirmed that the Young's modulus increased with the increase in the number of laser irradiation. Finally, based on these results, the deformation was measured by varying the amount of initiator and the number of laser irradiations, and it was confirmed that the deformation increased with increasing the amount of initiator and the specific number of irradiations. References Skylar Tibbits, " 4D printing: multi-material shape change", Archit. Des. 84, 116–121 (2014). https://doi.org/10.1002/ad.1710 MD Nahin Islam Shiblee, Kumkum Ahmed, Ajit Khosla, Masaru Kawakami, Hidemitsu Furukawa, "3D printing of shape memory hydrogels with tunable mechanical properties." Soft Matter 2018, 14, 7809. https://doi.org/10.1039/C8SM01156G Kumkum Ahmed, MD Nahin Islam Shiblee, Ajit Khosla, Larry Nagahara, Thomas Thundat, and Hidemitsu Furukawa. "Recent progresses in 4D printing of gel materials." Journal of The Electrochemical Society 167, no. 3 (2020): 037563. https://doi.org/10.1149/1945-7111/ab6e60 MD Nahin Islam Shiblee, Kumkum Ahmed, Masaru Kawakami, Hidemitsu Furukawa, "4D Printing of Shape-Memory Hydrogels for Soft-Robotic Functions." Adv. Mater. Technol. 2019, 4, 1900071. https://doi.org/10.1002/admt.201900071

Food 3D printers are next generation devices that can fabricate food products with complex internal structures and external shapes, and are expected to be used as devices for producing food products with shapes and textures that meet people's preferences, but also provide requirement of seven essential factors for a balanced diet: carbs, protein, fat, fiber, vitamins, minerals, and water [1, 2]. The food 3D printer can handle two types of food at the same time, and since it can form food in two colors, it can make food that cannot be made with a syringe nozzle. On the other hand, there are concerns about the shortage of protein supply due to the increase in population, and alternative meats that are not derived from livestock are attracting attention [3]. Currently, there are few reports of research on alternative meats using food 3D printers, and in particular, 3D modeling of alternative meat that reproduces the texture of actual meat has not been done much. In this study, we have developed a food 3D printer technology that enables the modeling of alternative meat that reproduces the texture of actual meat. We have investigated the composition of alternative meat materials suitable for 3D printing based on soy protein, and the material properties of the dough using a rheometer. In future, we will report on the movement and layering during the 3D food printing process. References: [1] Shunsuke Suzuki, Masaru Kawakami, Hidemitsu Furukawa, ”Food proreties suitable for 3D printer and effect on printing precsion” Materials and processing conference, 2018 [2] Suzuki, Shunsuke, Jun Ogawa, Yosuke Watanabe, MD Nahin Islam Shiblee, Ajit Khosla, Masaru Kawakami, Jun Nango, and Hidemitsu Furukawa. "Texture Control of 3D Printing: Effect of Internal Structure of 3D Printed Foods on their Fracture Process in Compression." ECS Transactions 98, no. 13 (2020): 59. [3] Kodama, Mai, Ryo Ishigaki, Samiul Basher, Hiroyuki Sasaki, Azusa Saito, Masato Makino, Ajit Khosla, Masaru Kawakami, and Hidemitsu Furukawa. "3D printing of foods." In Nano-, Bio-, Info-Tech Sensors, and 3D Systems II, vol. 10597, p. 1059718. International Society for Optics and Photonics, 2018.

Food 3D printing is expected to be a technology to create foods with different tastes and hardness depending on individual preferences and to solve the problem of food loss problems. In this study, we focus on the 3D printing of chocolate, whose product value is greatly affected by its appearance, entertainment and texture. Although 3D printers of chocolate are gradually appearing in the market, most of them only focus on the modeling of shape, and there are quite few printers that can form chocolate with designed texture. We develop a chocolate 3D printer using two chocolate materials. In addition to the syringe type extruder, we introduce the gear pump type extruder, which has a fine and stable extrusion. We 3d print chocolates with various internal structures using two chocolate materials and evaluate the differences in their textures by equipment measurement and by sensory tests. In addition, the melt-in-mouth feeling and the snappiness, which are important for the texture of chocolate, are investigated. In this presentation, we report the results of texture tests of black chocolate formed by a single syringe type 3D printer. References: Kodama, Mai, Yumiko Takita, Hideaki Tamate, Azusa Saito, Jin Gong, Masato Makino, Ajit Khosla, Masaru Kawakami, and Hidemitsu Furukawa. "Novel Soft Meals Developed by 3D Printing." Future Foods (2017): 161-181. Suzuki, Shunsuke, Jun Ogawa, Yosuke Watanabe, MD Nahin Islam Shiblee, Ajit Khosla, Masaru Kawakami, Jun Nango, and Hidemitsu Furukawa. "Texture Control of 3D Printing: Effect of Internal Structure of 3D Printed Foods on their Fracture Process in Compression." ECS Transactions 98, no. 13 (2020): 59. https://doi.org/10.1149/09813.0059ecst Rahman, Julkarnyne M. Habibur, MD Nahin Islam Shiblee, Kumkum Ahmed, Ajit Khosla, Masaru Kawakami, and Hidemitsu Furukawa. "Rheological and mechanical properties of edible gel materials for 3D food printing technology." Heliyon 6, no. 12 (2020): e05859. https://doi.org/10.1016/j.heliyon.2020.e05859

In this work, we present the structural analysis of 3D/4D printable N,N-dimethylacrylamide (DMAAm)-co-stearyl acrylate (SA) and/or lauryl acrylate (LA)-based shape memory gels (SMGs). We characterized these gels by scanning microscopic light scattering technique (SMILS) where a time- and space-averaged correlation function is obtained to overcome the inhomogeneous media. Thus, the characteristic size of the gel internal network (mesh size, ξ) and crosslinking densities are estimated from the Einstein–Stokes formula. The rheological study of the SMGs revealed information about their mechanical strength and transition temperature. From the experimental storage modulus measured by rheological study, crosslinking density and mesh size of the network were also calculated. Both the techniques suggest that SMG with high crystalline content of SA monomer in the gel network contain smaller mesh size (1.13 nm for SMILS and 9.5 nm for rheology study) and high crosslinking density. The comparative study between the light scattering technique and rheological analysis through the quantitative analysis of crosslinking densities will be important to understand the structural properties of the SMGs.

3D food printing sectors require comprehensive knowledge on viscoelastic and mechanical properties of diverse food materials in order to effectively utilize them in rapid and customized 3D production for supply and manufacturing chains. In this work, we present mechanical and rheological properties of Agar and Konjac based edible gels at different Agar and Konjac weight ratio and discuss their 3D printing performance. Gel samples with higher Konjac content positively contributed to the viscoelastic properties of the gel samples which in return has been found viable for extrusion-based 3D printing. By choosing appropriate printing parameters, different shapes are printed to demonstrate printing resolution. We expect, this study will add potential scope for evaluating and optimizing soft-gel materials for 3D food printing sector., 3D printing, Rheology, Mechanical properties, Edible gel, Food printing

Japan revised and implemented the Occupational Safety and Health Act in December 2015 to mandate that businesses with 50 or more workers have all of their workers tested for stress annually. In China, one effect of the “one child policy” and the nuclearization of the family has been that the number of children has decreased, while the number of elderly people living alone continues to grow. This growth is increasing the demand for long-term care workers. However, because the aging of the Chinese population has been more rapid than in Japan, and China has yet to develop a long-term care system to cope with the aging of its population, the burden on long-term care staff appears to be increasing. Although the resulting need for more support for long-term care staff has become an issue, China has yet to develop a mental health policy like that of Japan that mandates the monitoring of mental health, for example, through annual testing of workers for stress. As a result, the factors underlying long-term care worker stress have yet to be identified.This study attempted to discover, through a comparison of long-term care worker stress in Japan and China, the kinds of job-related stress care workers tended to have and what the principal underlying factors resulting in high levels of stress may be in each country. To that end, data were collected on workers’ psychological and physical stress using the Brief Job Stress Questionnaire (BJSQ) and analyzed to find out how stress may differ by country, gender, job responsibilities, having to work night shifts, or having certain qualifications.

In this work, we present the preparation, characterization, and 3D printing of highly conductive, soft, and functional nanocomposite polymers. The prepared nanocomposite is a polymeric system that consists of poly (ionic liquid) (PIL), polymethylmethacrylate (PMMA), and multiwalled carbon nanotubes (MWCNTs) as fillers and an ionic liquid (IL) that acts as a plasticizer and dopant for the MWCNTs. The nanocomposites exhibited variable mechanical (strain at break: 50–250%) and conductive properties depending on their composition, and the highest conductivity of 520 Sm−1 was attained with 15 wt.% MWCNT loading owing to the well-defined morphology of the MWCNTs revealed by SEM. The thermal properties of the nanocomposites were measured by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The results revealed high thermal stability up to 340 °C regardless of the composition and a variable transition temperature dependent on the MWCNT, IL, and polymeric contents. Finally, the conditions for 3D printing were optimized, and as a proof of concept, we demonstrated the fabrication of a flexible, 3D-printed circuit, which can be bent and twisted without damaging the circuit. Highly conductive, soft, and 3D-printable nanocomposite polymers have been developed that consists of poly (ionic liquid) (PIL), polymethylmethacrylate (PMMA) as polymeric system, multiwalled carbon nanotubes (MWCNTs) as fillers and an ionic liquid (IL) that acts as a plasticizer and dopant for the MWCNTs. The nanocomposites exhibited variable mechanical, conductive, and thermal properties depending on the composition of polymer, IL, and MWCNTs. Finally, we optimized the conditions for 3D printing and demonstrated the fabrication of a flexible, 3D-printed circuit, which can be bent and twisted without damaging the circuit.