Jin Gong

3D Printing of Meso-Decorated Gels and Foods

Two kinds of 3D printers were developed in our group. One is bathtub-type gel printer named SWIM-ER. The other is ink-jet-type food printer named E-CHEF NO.1. Using Meso-Decorated gels and agar, 3D printing of the soft materials was carried out. The valve of blood vessel, which is difficult to build by soft materials, is printed successfully by SWIM-ER. Their dimensions became almost the same as the designed. We also succeeded in printing food by E-CHEF NO.1, while a few bubbles are found in the sample.

Gel Engineering Materials Meso-Decorated with Polymorphic Crystals

Gels are a new material having three-dimensional network structures of macromolecules. They possess excellent properties as swellability, high permeability and biocompatibility, and have been applied in various fields of daily life, food, medicine, architecture, and chemistry. In this study, we tried to prepare new multi-functional and high-strength gels by using Meso-Decoration (Meso-Deco), one new method of structure design at intermediate mesoscale. High-performance rigid-rod aromatic polymorphic crystals. The strengthening of gels can be realized by meso-decorating the gels structure using high-performance polymorphic crystals. New gels with good mechanical properties, novel optical properties and thermal properties are expected to be developed.

Experiments of a variable stiffness robot using shape memory gel

This paper proposes a variable stiffness robot using a shape memory gel (SMG). Variable stiffness robots are useful to handle uneven objects in uneven environments such as home and office. Variable stiffness of rigid-link robots can be realized using motor control. Most of these robots require expensive force sensors. Flexible mechanical parts enable robots to realize low stiffness at the end-effectors without force sensors. However, high stiffness is hard to be realized by the robots with flexible mechanical parts. We propose another method to realize the variable stiffness of the robot without force sensors. We use a cold SMG for a rigid link and a hot SMG for a flexible link. A temperature control system of the SMG is developed, and any SMG link can be used as both a rigid link and a flexible link. Experiments of the application using the system are performed to illustrate the validity of our proposed method.

Silver nanowires embedded gel electrodes

The polyelectrolyte of high-strength gels was made to improve the mechanical properties in our previous study. In the field of electronic devices, the demand of polymer electrodes, which have high conductivity, high flexibility and transparence, is increasing. In this study, we attempt to make a transparent polymer electrode by laminating polymer thin film and silver nanowire (AgNW). High transparenct poly(methyl methacrylate) (PMMA) film, which is produced by using solvent cast method is used. AgNW is prepared by reacting Silver chloride (AgCl) with Silver nitrate (AgNO3) based on previous study. The AgNWs taking on different shapes were obtained. Fibrous AgNWs are formed by using high molecular weight polyvinylpyrrolidone (PVP). These results showed a possibility of developing the polymer electrode with high conductivity, high flexibility and transparence.

Characterization of Shape Memory Gels using Scanning Microscopic Light Scattering

In the present study, we characterize internal structure of shape memory gel with Scanning Microscopic Light Scattering (SMILS), which is typically a dynamic light scattering system developed in our laboratory. It is specialized for analyzing the microscopic structure of gels having scanning as well as multi-angle facility. Transparent shape memory gel is prepared by solvent free technique using two monomers. The ratio of N,N-dimethyl acrylamide (DMAAm) and Stearyl acrylate (SA) is 3:1 in molar ratio. The mesh size of internal network structure of shape memory gel is determined by the SMILS and it is found in several nm in size. The diffusion coefficient is calculated and the critical temperature is observed where gel is changed its phase.

Experiments of a two-arm robot using shape memory gel

Many robots are designed so that the number of their actuators is as small as possible to decrease their weight. In many cases, the number of actuators in robots is smaller than that of muscles in animals. We propose the method to increase the dexterity of the robot without increase of actuators. The link made from shape memory gel (SMG) is deformed to be suitable for each task of the robot. The methods of link deformation and shape recovery of a two-arm robot are presented. In the link deformation process, the SMG attached at one hand is deformed by the other hand. The shape memory function of SMG enables quick and simple shape recovery. That contributes efficient repetition of deformation and shape recovery process. Finally, we show the basic experiments using an upper body humanoid robot to show the validity of the method.

Processing and Thermal Response of Temperature-Sensitive-Gel(TSG)/Polymer Composites

Temperature-sensitive gels (TSGs) are generally used in the fields of medical, robotics, MEMS, and also in daily life. In this paper, we synthesized a novel TSG with good thermal durability and a lower melting temperature below 60 °C. We discussed the physical properties of he TSG and found it provided excellent thermal expansion. Therefore, we proposed the usage of TSG to develop a strategic breathable film with controllable gas permeability. The TSG particles were prepared firstly and then blended with linear low-density polyethylene/calcium carbonate (LLDPE/CaCO3) composite to develop microporous TSG/LLDPE/CaCO3 films. We investigated the morphology, thermal, and mechanical properties of TSG/LLDPE/CaCO3 composite films. The film characterization was conducted by gas permeability testing and demonstration temperature control experiments. The uniformly porous structure and the pore size in the range of 5–40 μm for the TSG/LLDPE/CaCO3 composite films were indicated by SEM micrographs. The demonstration temperature control experiments clearly proved the effect of the controllable gas permeability of the TSG and, more promisingly, the great practical value and application prospects of this strategic effect for the temperature-sensitive breathable film was proved.

The effect of cross linker concentration in the physical properties of shape memory gel

The shape memory hydrogels were synthesized and studied the physical properties. The gels were made by a hydrophilic monomer named N, N-dimethyl acrylamide (DMAAm) and a hydrophobic monomer named stearyl acrylate (SA). The water-swollen hydrogels show well transparency and shape memory property while gels absorb large water content. The properties were characterized by varying the cross-link concentration, whereas the concentration of other chemical components was remained constant. In this study, the DMAAm and the SA ratio was 3:1 to make one mole solution. It is observed that the swelling ratio slightly depends on the cross-link concentration at certain amount. However, mechanical properties strongly depend on the cross-link concentration. Thermal properties were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC spactra of dried samples exhibits complex crystalline nature, while swollen samples show homogeneous crystallinity. A well thermal stability is observed regard less of cross-link concentration.

3D gel printing for soft-matter systems innovation

In the past decade, several high-strength gels have been developed, especially from Japan. These gels are expected to use as a kind of new engineering materials in the fields of industry and medical as substitutes to polyester fibers, which are materials of artificial blood vessels. We consider if various gel materials including such high-strength gels are 3D-printable, many new soft and wet systems will be developed since the most intricate shape gels can be printed regardless of the quite softness and brittleness of gels. Recently we have tried to develop an optical 3D gel printer to realize the free-form formation of gel materials. We named this apparatus Easy Realizer of Soft and Wet Industrial Materials (SWIM-ER). The SWIM-ER will be applied to print bespoke artificial organs, including artificial blood vessels, which will be possibly used for both surgery trainings and actual surgery. The SWIM-ER can print one of the world strongest gels, called Double-Network (DN) gels, by using UV irradiation through an optical fiber. Now we also are developing another type of 3D gel printer for foods, named E-Chef. We believe these new 3D gel printers will broaden the applications of soft-matter gels.

Nanoscale imaging of mesh size distribution in gel engineering materials with visual scanning microscopic light scattering

Gels have unique properties such as low frictional properties, permeability and biocompatibility due to their high water content. When the gels are developed as industrial materials, we need to establish a method of quantitative analysis derived from the internal structure and the mechanical properties of these gels. However, the static inhomogeneities in gels prevent us to observe the structure of gels by scattering method. To solve this problem, we have developed scanning microscopic light scattering (SMILS) originally. In this study, firstly, the internal structure of the dry-synthesis gels are precisely examined experimentally by the scattering microscopic light scattering and theoretically by the tensile test. By comparing the two quantities, the dense network structure makes the mechanical properties of gels smaller than theoretical estimation. Secondary, we show the new system named Visual-SMILS that can provide the 2-dimentional data of the distribution. Based on our findings, the strength of the gels can be controlled and expected. We believe the Visual-SMILS system will promote research significantly in the field of gels.