bluuebunny/crossref_metadata_2025 huggingface dataset:
Variational Multiscale Modeling of Lithium Batteries
Authors: Liu John , Liu Lin
Published: February 2020

Batteries are required to have higher energy and power density to meet the requirement of future electric vehicles and other power supply applications. To ensure the safety and durability of the high energy lithium batteries, the numerical study is the key to understanding and design of the next generation batteries. More importantly, the modeling and simulation study of lithium batteries help us understand the underlying causes of the electrochemical, electrical, thermal, and mechanical performance of a lithium battery under various operating conditions. However, the traditional modeling method of lithium batteries assumes the homogeneous structure and reaction to reduce the complexity of the model. The heterogeneity of the battery electrodes significantly impacts the performance of a battery. Due to the complex microstructure of the battery electrodes, it requires ultra-fine meshes to model the various length scales of the electrode structure, which requires very high computing power. This high computational cost is not practical for the numerical optimization design and long-term cycling simulations. Therefore, a variational multiscale method (VMM) is the key to model a lithium battery with considering the heterogeneity. The proposed VMM model reduces the computational cost of a realistic 3D battery model without compromise the accuracy of the heterogeneity. The VMM splits the battery model into macro-scale and micro-scale. By applying the micro-green function, which was firstly developed by Hughes [1] and then extended to battery modeling by us [2], as illustrated in Fig. 1, the micro-scale problem is analytically solved through the projection based on the macro-scale solution to obtain more accurate results. By doing so, we can significantly increase the computational efficiency and accuracy of conducting complex battery multi-scale simulations. With this method, we can simulate battery degradations in the realistic microstructure over hundreds of charge and discharge cycles with a reasonable computational cost. With the understanding of the battery behavior over long-term cycling, the battery electrodes can be redesigned to obtain longer lifetime and better performance through the numerical optimization for energy storage applications.

[1] T.J. Hughes, G. Sangalli, Variational multiscale analysis:
the fine-scale Green’s function, projection, optimization, localization, and stabilized methods. SIAM Journal on Numerical Analysis, 2007. 45(2): p. 539-557.

[2] L. Liu, M. Moradi, Towards a More Realistic Battery Model: Variational Multiscale Modeling of Li-Ion Batteries, ECS Transactions, 2017. 77(11): p. 273-291

Figure 1
(Invited) On the EIS Response of Composite Insertion Electrodes – Toward a Better Understanding of Porous Electrodes
Authors: Gruet David , Delobel Bruno , Lucas Ivan , Sicsic David , Vivier Vincent
Published: February 2020

Electrochemical Impedance Spectroscopy (EIS) is a powerful tool to assess and understand the degradation of Li-ion battery (LIB) performances during operation (upon charge and discharge cycles). The full interpretation of EIS spectra of LIB can be however tedious because these systems are composed of porous electrodes and complex electrolyte. Moreover, side reactions, such as the formation of an insulating layer around the particles of the porous electrodes, can occur in battery operation modifying the impedance response.

A way to improve the interpretation of impedance data of LIB is the use of modeling. Most of the time, data interpretation is limited to the use of Electrical Equivalent Circuits (EEC) but the link between EEC and the physical processes involved in the system is ambiguous and difficult to establish. However, in the 60’s, Newman et al. [1] devised a model for porous battery electrodes. Their model describes the whole battery system thanks to equations that are directly related to the physical phenomena occurring in the composite electrodes. This model is still widely used in the battery field to simulate galvanostatic charge and discharge. Based on their work, and inspiring by works already done on modeling of EIS [2], it is possible to devise a model by linearizing all the equations [3]. The model obtained can then be directly connected to the physical phenomena occurring inside the porous electrodes which will greatly help to interpret EIS spectra.

In this work, we developed an analytical solution for the electrochemical impedance of a porous electrode composed of spherical intercalation particles in contact with concentrated electrolyte. The proposed model which is based on the concentrated solution theory but which also considers kinetics limitations and both solution-phase and solid-phase diffusion limitations, can predict the EIS response of a porous electrode at any state of charge using a limited set of parameters. Moreover, the developed model can predict the optimal porosity of the electrode to be targeted during the manufacturing process for the best cycling performances depending on the composition of the electrode (volume fractions of active material, binder, and conductive agent).

(1) Newman, J.S.; Tobias, C.W. Journal of the Electrochemical Society
1962
, 109(12), page 1183-1191.

(2) Meyers, J.P. et al. ; Journal of the Electrochemical Society
2000
, 147(8), page 2930-2940.

(3) Huang, J.; Zhang, J.B. Journal of the Electrochemical Society
2016
, 163(9), page A1983-A2000.
Proton Transfer Can Occur at High Rates through Single-Layer Graphene in Nafion | Graphene | Nafion Sandwich Structures
Authors: Creager Stephen E , Bukola Saheed , Korzeniewski Carol , Harris Joel Mark
Published: February 2020

Hydrogen pump cells fabricated from Nafion membranes and Pt-on-carbon electrodes were used to measure rates of proton transfer across single-layer graphene embedded in Nafion | graphene | Nafion sandwich structures. Single-layer graphene prepared by chemical vapor deposition onto copper foil was sandwiched between Nafion membranes by a series of hot-pressing steps coupled with chemical etching to remove the copper. Proton current densities in excess of 1 A / cm2 were observed for proton transfer across the graphene at cell bias voltages less than 200 mV. Confocal Raman spectroscopy measurements of the Nafion / graphene sandwich structures are consistent with single-layer graphene having very few structural defects embedded between Nafion membranes. Ion-transfer rates for lithium, sodium, potassium, and other cations were also measured and found to be much lower than rates for proton transfer, in most cases by many orders of magnitude. Two-layer and few-layer (3-5 layer) graphene sandwich structures were also studied and found to give proton currents much lower than single-layer graphene. Proton currents are described in terms of an area-normalized resistance following correction for all other contributions to series resistance in the cells. Resistances are then analyzed in terms of a rate constant for proton self-exchange across graphene.

Figure 1
3D Porous Carbon Networks Decorated Metal-Organic Framworks and Their Derivates for Energy Storage
Authors: Deng Xiaoyang , Ma Liying , Zhao Naiqin
Published: February 2020

Metal organic frameworks (MOFs) assembled by metal ions with organic linkers are one of the most promising porous crystalline materials due to their tunable porosity, wide varieties, large specific surface area and excellent physical and chemical performance.[1] But the instability and electron conductivity of most MOFs are poor. The micropore structures restrain the infiltration of electrolyte and the transport of mass ions in electrochemical process, which hinder the application of MOFs in energy storage as a result.[2,3]

Recently, the rational structure design has been demonstrated as an effective path to circumvent the above-mentioned drawbacks. Especially, 3D carbon network (3DCN) has been employed as a conventional substrate to fabricate the composites because of its high electrical conductivity, controllable pore-size distribution and interconnected porous network.

Herein, we report a facile nanoconfined strategy to prepare the MOF-3DCN composite with Ball-in-Cage nanostructure. The unique “Cage” frame not only controls the ZIF-67 particle size, but also ensures a high electron conductivity of the entire structure, which displays high electrochemical performance in supercapacitor. It can be transformed into metal oxide or sulfide/carbon composites through thermal treatment methods. The MOF-derived materials show great storage performances for lithium-ion batteries as well. Furthermore, another 3D carbon network was served as the matrix for the ZIF-8 nanoparticles fabrication. A spider-web-like carbon pattern formed on 3DCN surface enhances the mass-transfer ability and takes the advantages of ZIF-derived carbon, which shows great potential in the electrolyte-based energy storage applications.

References

Song, D.;Qi-Long, Z.; Qiang, X.: Nanomaterials derived from metal–organic frameworks. Nature Reviews Materials 3, 17075 (2017).

Wu, H. B.;Lou, X. W. D.: Metal-organic frameworks and their derived materials for electrochemical energy storage and conversion: Promises and challenges. Science Advances 3, 9252 (2017).

Ke, C.;Zhenhua, S.; Ruopian, F.; Ying, S.; Hui-Ming, C.; Feng, L.: Metal-Organic Frameworks (MOFs)-Derived Nitrogen-Doped Porous Carbon Anchored on Graphene with Multifunctional Effects for Lithium-Sulfur Batteries. Advanced Functional Materials. 1707592 (2018).
The Inductive and Capacitive Characteristics of Carbonate-Derived Carbons
Authors: Hughes Matthew , Allen Jessica A , Donne Scott W
Published: February 2020

Due to the increasing modern dependence on electronic devices, the production of carbon materials for supercapacitive and battery-based applications is an area of current research and innovation. It has been known for a considerable time that carbons can be formed through the electrolytic reduction of molten carbonate salts [1], however, little research has been put into in-depth understanding of the electrochemical characteristics of these materials. Electrochemical impedance spectroscopy can tell us a lot about the suitability of these materials for supercapacitive applications. This research investigates how the characteristics of carbons derived through molten carbonate reduction change based on synthesis conditions, with a particular focus being placed on the inductive and capacitive behaviour of the materials and on how inductances arise (Figure 1 (i)). This is done through the application of equivalent circuit modelling (Figure 1 (ii)) to cells constructed from synthesised and activated carbons, and the subsequent mathematical modelling of the system using complex non-linear least squared error curve fitting (CNLS) based on the interior-point algorithm in the MATLAB program. The frequency-dependant capacitance of the materials (Figure 1 (iii)) is reported and used as a point of comparison. Optimal carbon synthesis conditions of 500°C or low deposition current densities of 0.15 A/cm2 have been found to both reduce inductive behaviour, and to produce carbons with capacitances as high as 160 F/g, close to 90% of that of the examined activated carbon.

[1] Hughes, M.A., J.A. Allen, and S.W. Donne, Carbonate Reduction and the Properties and Applications of Carbon Formed Through Electrochemical Deposition in Molten Carbonates: A Review. Electrochimica Acta, 2015. 176: p. 1511-1521.

Figure 1
Carbon Quantum Dots in Novel Photosystem I-Based Photovoltaics for Enhanced Photocurrent
Authors: Stachurski Christopher , Jennings G. Kane , Cliffel David E.
Published: February 2020

Although modern photovoltaics have reached internal quantum efficiencies greater than 50%, it has come at the expense of requiring extensive synthetic conditions and materials harmful to the environment. As an alternative, our group has turned to a class of bioinspired photovoltaics using Photosystem I (PSI), a robust membrane protein complex found in plants, to generate photocurrent when interfaced with semiconductive materials. Although functional PSI devices have been made using a variety of materials (silicon wafers, nanoporous gold, graphene) they often require extensive processing of the materials and harsh experimental conditions. Furthermore, the observed photocurrent densities tend to suffer from poor contact at the protein-electrode interface.

In this work, an emerging class of carbon semiconductors, carbon quantum dots (CQDs), will be synthesized to promote charge separation in PSI photovoltaic cells. Through a facile, one-step solvothermal synthesis, CQDs electronically compatible with PSI can be made from common carbon precursors and novel small molecule dopant sources, cutting the cost and environmental impact of our devices. Following purification, the as produced CQDs exhibit tunable band energetics as a result of varied synthetic conditions allowing for precise band alignment. Thanks to their small size and modifiable carbon surface, CQDs are compatible with a number of coupling strategies allowing for a more uniform PSI-CQD interface, potentially enhancing the observed photocurrent densities. This study will open the door to a low-cost, organic photovoltaic whose fabrication could generate significantly higher photocurrent, easily be scaled-up or used in non-laboratory settings.
(Invited) Water-Soluble Biopolyimides with Ultrahigh Performances
Authors: Kaneko Tatsuo , Dwivedi Sumant , Takada Kenji
Published: February 2020

Bioplastics are indispensable for establishment of green-sustainable society. Conventional bioplastics composed of aliphatic polymers like poly(lactic acid)s are successfully circulated as a specific field. In order to widen the field of bioplastics, aromatic bio-based polymers are required. Under this background, we have prepared aromatic biopolymers derived from exotic biochemicals with rigid backbones [1-3]. Here we used 4-aminocinnamic acid (4ACA) which was bioavailable by a microorganismal genetic-engineering. The photodimer of 4ACA was successively prepared as a bio-derived aromatic diamine via [2+2] cycloaddition in the solid state with a perfect conversion degree by illumination of UV-LED. The biodianilines were polymerized with diisocyanates, diacids, and tetraacid dianhydrides to produce aromatic polymers such as polyureas, polyamides, and polyimides, respectively. Almost bio-based polymers prepared here showed a high transparency, high heat-resistance, and high mechanical strength. Especially the biopolyamide showed extremely-high fracture strength around 400 MPa as high as those of high-tensile steels, in spite of amorphous structure [3]. The optimization of the biopolyimide structure gave the fantastic properties of ultrahigh toughness comparable with those of spider silks. On the other hand, the aromatic polyimides derived from the bio-photodimer with cyclobutanetetracarboxylic dianhydrides showed a good thermomechanical performance as well as low density around 1.05-1.28 g/cm3, and additionally showed a high transparency [2,4]. These thermal/mechanical performances are higher than those of conventional transparent polymers, in spite of limited molecular design by bio-based molecules. Additionally we found that the water-solubility was imparted in polyimide materials when the side carboxylate groups were ionized, which was a surprizing phenomenon because the aromatic polyimides are generally insoluble in any solvents.

Acknowledgement: The authors gratefully acknowledges Grant-in-Aid supports from ALCA (5100270) of JST, Japan and from Scientific Research (B) (15H03864) of MEXT, Japan.

References:

[1] T. Kaneko, et al., Nature Mater., 5, 996-970 (2006)

[2] P. Suvannasara, T. Kaneko et al. Macromolecules, 47, 1586-1593 (2014)

[3] S. Tateyama, T. Kaneko et al. Macromolecules, 49, 3336-3342 (2016)

[4] G. Liou, T. Kaneko, et al. Nanoscale, 8, 12793 (2016)

Figure 1. Typical structure of biopolyimide prepared from microbial aromatics

Figure 1
(Invited) Instantly Formative Hydrogels with Super-Low Polymeric Component
Authors: Sakai Takamasa
Published: February 2020

Hydrogels are water-filled materials with characteristics similar to those of biological soft tissues and have broad application as biomaterials. However, the safety of hydrogels is difficult to guarantee throughout the full life cycle in vivo due to the inevitability of degradation-induced swelling. Indeed, the swelling pressure exerted by conventional hydrogels is sufficiently large to cause severe adverse reactions to surrounding tissues. In this respect, we report here a new class of in situ forming hydrogels that guarantee safety throughout the full life cycle. The oligo-TetraPEG hydrogel has an extremely high water content and a polymer content of only 4.0 g/L, resulting in an exceptionally low swelling pressure.

The oligo-TetraPEG hydrogel was successfully injected and gelled inside a living body within a clinically relevant manipulation time and little cytotoxicity. The oligo-TetraPEG hydrogel exhibited an appropriate stiffness, similar to that of soft tissue, with extremely low swelling pressure thus being compatible with living tissues. The oligo-TetraPEG hydrogel functioned as an artificial vitreous body for over a year without any adverse effects, and was effective for treating retinal detachment as an intravitreous tamponade material．The present concept provides new guidance for the safety of biomaterials in vivo.

Figure 1
(Invited) A Thermo-Responsive Cationic Comb-Type Copolymer Enhances Membrane Permeabilizing Activity of an Amphiphilic Peptide
Authors: Masuda Tsukuru , Shimada Naohiko , Maruyama Atsushi
Published: February 2020

Amphiphilic peptides are great focus owing to potential applications including drug delivery systems and antimicrobials. E5 peptide, one of amphiphilic peptides, forms amphiphilic α-helix at low pH, and exhibits membrane permeabilizing activity.1,2) However, the activity of E5 peptide is low attributed to low solubility in aqueous media. In the previous paper, we showed that the cationic comb-type copolymer, poly(allylamine)-graft-dextrane (PAA-g-Dex) formed soluble inter-polyelectrolyte complex (sIPEC) with E5 peptide at both low and natural pH, and E5/PAA-g-Dex exhibited strong membrane disruptive activity.3) In this study, we designed a novel comb-type cationic copolymer composed of a PAA main chain and thermoresponsive poly(N-isopropylacrylamide) graft chains (PAA-g-PNIPAAm). We hypothesized that the thermoresponsive hydrophilic/hydrophobic transition of the grafted polymer would regulate the membrane disruption activity of E5 peptide.

The target copolymer was prepared by activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). The ratio of AA units to Initiator to NIPAAm units was estimated to be 100:9:421 by 1H NMR. Thus, the number-averaged molecular weight (M
n) of PNIPAAm and the PNIPAAm contents were 1.0 × 104 and 94.3 wt %, respectively. Circular dichroism (CD) spectra measurement revealed that PAA-g-PNIPAAm formed sIPEC with E5 peptide, resulting in α-helix formation of E5 peptide. Furthermore, the complex formation of E5 and PAA-g-PNIPAAm was investigated by measuring the fluorescence spectra of triptophan residure in E5 peptide. From these investigations, we found that the interaction between E5 peptide and PAA-g-PNIPAAm at 35 °C (above LCST) was stronger than that at 25 °C (below LCST). These results suggest that the hydrophobicity of the environment around the cationic polymer chain influences complex formation. E5 peptide in the presence of PAA-g-PNIPAAm induced the leakage from liposomes, whereas E5 peptide alone did not. Importantly, E5/PAA-g-PNIPAAm induced more significant leakage at 35 °C than at 25 °C. Thus, membrane disruptive activity of E5/PAA-g-PNIPAAm sIPEC was regulated in response to temperature coupled with the phase transition of the thermo-responsive grafted chain.4)

References: 1) M. Murata, et al., Ohnishi, J. Biol. Chem.
1991, 266, 14353. 2) M. Murata, et al., Biophys. J. 1993, 64, 724. 3) N. Shimada et al., J. Controlled Release
2015, 218, 45. 4) T. Masuda et al., Biomacromolecules
2018, 19, 1333.

Figure 1
(Invited) Development of Joint-linker Type Network Polymers - from Gels to Porous Polymers
Authors: Naga Naofumi
Published: February 2020

“Joint-linker type gels”, which are synthesized by addition reactions between multi-functional compounds as joint molecules, and a,w-bifunctional compounds as linker molecules, have been developed in various systems. The resulting gels formed homogeneous network structure. The network structure (geometry of the network, mesh size) in the gels can be controlled by molecular structure of the joint molecule and length of the linker molecules. Click-type reactions are usable to synthesize the various types of the joint-linker type gels in various solvents. Compatibility between network structure and solvents affected the mechanical properties. Recently, we found that phase separation induced by the network formation in the gels yielded porous polymers in various reaction systems. The porous structure was controllable by the reaction conditions, monomer concentration, reaction temperature, and so on. Most of the joint-linker type porous polymers were unbreakable by compression test. The porous polymers also absorbed many kinds of solvents.
(Invited) Soft Matter and Soft-Bodied Robots that Exploits its Mechanical Property
Authors: Umedachi Takuya , Kawahara Yoshihiro
Published: February 2020

To design a robot that moves around the natural environment and our daily environment like an animal, it is necessary to build a robot with flexible and deformable materials to imitate their muscles, tendons and deformable skins. This allows a robot to easily interact with a complex environment, to acquire richer sensory information resulting from the interaction, and to use the local sensory feedback to generate functionalities (e.g., locomotion). This talk introduces soft-bodied robots we have developed as case studies to show how to design, how to fabricate, and how to control. Furthermore, we would like to discuss the benefits from the perspective of not only material scientists and also roboticists.
(Invited) Designed Polymers for Antifouling Surfaces
Authors: Ando Tsuyoshi , Totani Masayasu , Yamamoto Ikuo
Published: February 2020

There is a strong demand for antifouling surface. To create such antifouling surface, there are some approaches such as chemical reaction at the surface, coatings, internal additives, etc. We are developing polymers that can modify the surface property by easy treatments based on precise design and synthesis of the polymers.

Biomedical synthetic materials, such as poly(ethylene terephthalate) (PET) and polypropylene (PP), are prone to adhesion of proteins, cells, and bacteria, causing functional failures in implants, artificial organs, catheters, and diagnostic devices, and increasing the risk of secondary infections. One of the promising answers is a hydrophilic polymer brush surface on which many polymer chains are connected in high density to inhibit adsorption of proteins and following adhesion of related biomolecules and cells. Such high density polymer brush is usually built by surface-initiated living radical polymerization through several chemical steps and polymers applied for medical devices are rather inert to chemical modification than inorganic materials. We thus created a new star shaped heteroarm polymer consisting of hydrophilic chains, as an antifouling block, and hydrophobic chains, as a substrate attaching block, for a biocompatible coating material, which is supposed to form polymer brush-like structure by simple coating procedure. The coating surface exhibited very good resistance to adhesion of platelets, bacteria, fibroblasts, and proteins although the corresponding linear polymer exhibited moderate resistance. This result indicates utilization of unique architecture of the star polymer is effective for building condensed polymer brush structure at the surface.

Perfluoroalkyl group-containing polymer shows water/oil repellency. Although long perfluoroalkyl groups (longer than C8) exhibit high repellency, they can not be employed because of the environmental reason, nowadays. Shorter perfluoroalkyl groups (less than C8) give less effect to environment but they have less repellency. We thud designed block copolymers consisting of fluorine and non-fluorine containing monomers and evaluated the sequence effects as an internal additive to PP resin to improve oil repellency. By controlling fluorinated/non-fluorinated monomer sequence, the oil repellency of the fluorinated polymer-added polypropylene (PP) was dramatically improved compared to that modified with the randomly sequenced fluoropolymer. For instance, random copolymer consisting of 2-(perfluorohexyl)ethyl methacrylate (C6FMA) and stearyl methacrylate (StMA) gave slightly higher contact angle (13º) than that of non-additive PP (6º). Compared to the random copolymer, the diblock and triblock copolymer lead much higher contact angles (23º and 38º, respectively) when only 1wt% of the fluoropolymer was mixed into PP. This result indicates sequence regulation of fluorinated/non-fluorinated monomer in the fluoropolymer is effective to concentrate fluorine groups at the resin surface resulting in improvement of water/oil repellency.
Effect of Starch on the Equilibrium of Boric Acid
Authors: Kobayashi Atsushi , Hoshino Yuto , Kamizawa Nanami , Itoh Hiroshi , Numata Yasushi
Published: February 2020

We have reported that behavior of starch depended on the existing of boric acid. Noteworthy, gelation behavior of soluble starch, one of the modified starch, was different from other native starches. Critical concentration of starch gelation (CCSG), in other words, the minimum concentration of starch to form gel, was increased as the amount of boric acid increased when soluble starch was employed. On the contrary, CCSG of native starches (corn, wheat, and potato) was decreased as the amount of boric acid increased. We have also tested drying process of gelatinized starches to evaluate the effect of boric acid on the water-holding ability of starch. When soluble starch was employed, no difference of the rate of water loss from gelatinized starch at 100 °C was observed, irrespective of the existing of boric acid. In contrast, the drying rate of native starches were strongly affected and suppressed in the presence of boric acid. Based on these fact, we assumed that the effect of boric acid changes depending on the type of starch. It is well known that boric acid B(OH)3 is shifted to B(OH)4
- above pH 9.24. Therefore, dry tolerance of gelatinized starch was expected to be shifted by pH value. To confirm the effect of pH on the dry tolerance of gelatinized starch in the presence of boric acid, we measured the rate of water loss from gelatinized starch at 100 °C. The rates of the water loss from all tested starches were shifted to be smaller by increasing pH value. The rate of water loss from native starches were gradually shifted to be smaller, while that from soluble starch dropped between pH 9 and 10. Kinetic analysis of water loss from gelatinized starch revealed that there were two phases in the process of water loss from gelatinized starch until complete water loss. Then, we analyzed the initial stage of the dry process by regarding this process as the first order reaction. Plots of the rate constant, k value versus pH value showed like titration curves in every dry process of starches. Interestingly, inflection point of the dry process using soluble starch differed from native starches. The inflection point was around pH 9, whereas those of native starches were around pH 8. This fact indicates the equilibrium of boric acid may vary by depending on the type of starch. To investigate that change of the equilibrium of boric acid in the presence of starch, gelatinized starch in the presence of boric acid were measured by Raman spectroscopy. Raman spectra of gelatinized starch in the presence of boric acid revealed much amount of starch inhibited change of three-coodinated boric acid to four-coodinated even in high basic aqueous solution. Detailed analysis is currently being investigated and will be presented at this meeting.
Development of Physical Property Measuring Device for 3D Food Printer Gel
Authors: Ishigaki Ryo , Kodama Mai , Khosla Ajit , Kawakami Masaru , Furukawa Hidemitsu
Published: February 2020

In recent years, research and development of 3D food printers have been actively conducted, and it is expected to change the future food problems immensely and the way of food manufacturing and processing.

In the Food Layer Manufacturing(FLM) 3D food printer, the molding conditions must be set for physical properties of the each material. In the previous study, researches were conducted on the relationship between viscosity and molding conditions by rheometer or viscometer, and it is reported that the modeling accuracy improves as viscosity increases. However, since it is difficult to use a rheometer or a viscometer at each household, a simple physical property measuring device is necessary. Therefore, in this study, we will investigate whether the shaping conditions can be determined from the concentric circle spreading out of the container after vibrating the gel contained in the cylindrical container with the diaphragm. Also, We will confirm whether or not it is possible to measure simple kinematic viscosity of a high viscosity material by checking the presence or absence of concentric circle spread and viscosity relationship.
Synthesis of Sulfur-Rich Nanoparticles with Sulfur/Thiophene-Based Cross-Linked Cores
Authors: Otsuka Hiroki , Chen-Tsyr Lo , Nakabayashi Kazuhiro , Mori Hideharu
Published: February 2020

Sulfur-rich polymeric nanoparticles (S-NPs) in which the core was cross-linked using thiophene-based cross-linking agents and sulfur were synthesized from the amphiphilic block copolymer, by site-selective cross-linking reaction. The amphiphilic block copolymer; Poly(PEGMA)-b-poly(DB3VT) was synthesized by RAFT polymerization. DLS measurement demonstrated the formation of stable S-NPs with uniform sized, which can be controlled by the amount of the cross-linking agents and reaction conditions (D
h = 110 nm, 150 nm in THF). UV-vis, fluorescence, and CV measurements led to the optical and electrochemical properties defined from polysulfide and oligothiophene. It was also suggested that HOMO and LUMO can be controlled by changing the cross-linking agent.

Figure 1
Preparation of Multiple Parallel Protein-polysaccharide Hybrid Gel Filaments Under Shear
Authors: Takayama Yuriko , Kato Norihiro
Published: February 2020

Fabrication of anisotropic gel with characteristic structures has been reported using a flow system with three dimensional microfluidic devices. Such gel structures are mainly achieved by design and preparation of the microchannel for flowing pre-gel solution. In this research, we propose a method for preparing multiple parallel gel filaments by controlling viscoelastic properties of polymer assembly as the fluid of microfluidic devices.

To promote the formation of heterogeneous assembly of different types of macromolecules, an aqueous two-phase separation (ATPS) technique was utilized. Two layers of aqueous solutions appear when the ATPS conditions including ionic strength, temperature, and solute concentration in certain combinations of two components are satisfied. In respective phase, some solute molecules form heterogeneous assemblies because the solutes in respective phase are highly concentrated. We previously reported that the alginate (Alg) could form the assembly with polyethylene glycol (PEG) in the induced phase of Alg/PEG/NaCl system. In aqueous media, the Alg assembly has the rigid structure because diaxial linkages in a successive region of guluronic acid are stabilized by hydrogen bonds. Destruction of hydrogen bonds of Alg molecules by interaction with PEG enables deformation of Alg assembly by shear.

Gel filaments were prepared with a co-axial flow device as double glass tubes, where an inner tube (inner diameter 0.7 mm) was fixed at the insert position of the outer tube. Pre-gel solution and crosslinker solution respectively were flown to inner and outer tube using syringe pumps. The morphology of the gel filaments was observed by a scanning electron microscope.

A single thick gel filament was obtained from aqueous sodium alginate solution, whereas multiple thin gel filaments were obtained when a mixed solution of Alg and PEG under the ATPS condition. Appearance of shear-thinning behavior for the Alg-rich phase suggests that the complexation of Alg with PEG was responsible for destruction of the rigid assembly due to breaking hydrogen bonds. In this poster, the method will be applied to the protein containing system to fabricate the protein-polysaccharide hybrid filaments.
(Invited) Photo Stimuli Responsive Supramolecular Actuators Constructed By Non-Covalent or Topological Crosslinkers
Authors: Takashima Yoshinori
Published: February 2020

Various kinds of biological molecular motors, such as myosin, kinesin, and dynein, realize the conversion of energy in ATP hydrolysis into mechanical work. These mechanical motions inspired supramolecular chemist to realize polymeric materials with supramolecular materials. Two structural approaches may realize supramolecular actuators through host–guest interactions: a method with a linear main chain and one with a side chain in the polymer structure (Fig. 1).1) We have prepared photo responsive supramolecular actuators by integrating host–guest interactions on the polymer side chains (Fig. 1a). The association and dissociation of inclusion complexes as crosslinking units on the polymer side chains demonstrate contraction and expansion motions due to changes in the crosslinking density. A plate-shaped actuator bent against the incident ultraviolet (UV) light. 2)

Herein we hypothesize that polymer chains crosslinked with [c2]daisy chains would realize a novel supramolecular actuator whose volume contracts upon UV light irradiation but expands upon visible (Vis) light irradiation. This contraction would bend the flat plate actuator toward the incident UV light because UV irradiation causes the shrinkage of the end-to-end distance of the [c2]daisy chain to shrink polymeric materials due to desorption of the solvent on the exposed surface (Fig. 1b). Supramolecular hydrogels containing CD-based [c2]daisy chains as crosslinkers contract and expand through photoresponsive sliding motions of the [c2]daisy chain (Fig. 1c).3) The photogenerated supramolecular artificial muscle is reminiscent of contraction and expansion motions of biological skeletal muscle.

Figure 1. Supramolecular actuators using cyclodextrin derivatives. These supramolecular actuators show macroscopic contraction–expansion and flexing behaviors.

References

(1) Harada, A.; Takashima, Y.; Nakahata, M. Acc. Chem. Res.
2014,
47, 2128-2140.

(2) Takashima, Y.; Hatanaka, S.; Otsubo, M.; Nakahata, M.; Kakuta, T.: Hashidzume, A.; Yamaguchi, H.; Harada, A. Nat. Commun.
2012,
3, 1270.

(3) Iwaso, K.; Takashima, Y.; Harada, A. Nat. Chem.
2016,
8
, 625–632.

(4) Takashima, Y.; Harada, A. J. Incl. Phenom. Macrocycl. Chem.
2017,
87, 313-330.

Figure 1
Real-Time Volume Changes in Individual Hydrogel Microspheres Observed By High-Speed AFM
Authors: Matsui Shusuke , Uchihashi Takayuki , Suzuki Daisuke
Published: February 2020

Many thermo-responsive polymers show a lower critical solution temperature (LCST), and thus they display a coil-globule transition across the LCST by changing temperature. Hydrogel microspheres (microgels) composed of thermo-responsive polymer are taken over the property from the polymer, as a result, they show a volume phase transition temperature around the LCST. Owing to their rapid temperature-responsiveness, microgels are expected the various application such as sensors and separation technology [1]. Thermo-responsive properties of the microgels have been mainly evaluating by light scattering so far because typical size range of the microgels are tens nanometer to sub-micron order, which can not be clearly observed by optical microscopy. Against this background, the real-time volume transition of individual microgels during heating was visualized for the first time using high-speed atomic force microscopy (HS-AFM) [2]. This method allows the direct visualization of the structural dynamics of biological molecules in action, without significantly disturbing the physiological function of the molecules [3-4], and allows the monitoring dynamic adsorption behavior of microgels onto solid substrate in aqueous solution [5]. The microgels were synthesized from N-isopropyl acrylamide and cross-linker N,N'-methylenebis(acrylamide) with different content by aqueous free-radical precipitation polymerization. In the present study, we will discuss the real-time changes in morphology of the microgels.

Partially reproduced with permission from [5] Copyright (2017) John Wiley and Sons.

References

[1] F. A. Plamper, W. Richtering, Acc. Chem. Res., 50, 131 (2017)

[2] S. Matsui et al., in preparation

[3] T. Ando, T. Uchihashi, T. Fukuma, Progr. Surf. Sci., 83, 337 (2008)

[4] T. Ando, T. Uchihashi, S. Scheuring, Chem. Rev., 114, 3120 (2014)

[5] S. Matsui, T. Kureha, S. Hiroshige, M. Shibata, T. Uchihashi, D. Suzuki, Angew. Chem. Int. Ed., 56, 12146 (2017)
Evaluation of Gel Touch Sensor
Authors: Hara Yuta , Yoshida Kazunari , Ahmed Kumkum , Khosla Ajit , Kawakami Masaru , Furukawa Hidemitsu
Published: February 2020

The polymer gel is composed of polymeric chains which are crosslinked in a three-dimensional (3D) network structure and liquid which is widely applied to tissue engineering, medical treatment, and solid state electrochemical devices. The gel contains a large amount of water inside the three-dimensional network structure. The human body is also mostly composed of water, hence, the percentage of water in human body is relatively high similar to hydrogel.

Among various kind of gel, ion gel possessing ionic liquid is beneficial for applications since ionic liquids are liquid salts at room temperature and have useful properties such as non-volatility, non-inflammability, electrochemical stability, thermal stability and high ionic conductivity. In this study, we investigated the piezoelectric properties of ion gels to apply them for touch and pressure sensors in soft-matter robotics.

In this study, the used ion gel was made utilizing thiol-ene reaction and was composed of thiol monomer. The thiol-ene reaction is hardly influenced by the surrounding environment, hence, we can easily make ion gel. In addition, it is possible to form any objects using a photopolymerization initiator and a 3D printer. The aim of this research is to develop a tactile sensor using ion gel having non-volatility, non-flammability, thermal stability, high conductivity and softness close to humans.

For the preparation of ion gels, the monomers pentaery thritol tetralcis (3-mercaptobutylate) and dipentaerythritol hexakis (3-mercaptopropionate), crosslinker 1,6-Hexanediol diacrylate, initiator benzophenone, solvent ionic liquid 1 - buty - 3methylimidazolium bis (fluorosulfonyl) imide were used. For the experiment, a friction tester, LCR meter and temperature controller were used.

Here we report the relationship between frequency of applied alternating current, electric resistance of ion gel, applied load, and temperature. The sizes of sample gel plates are 50 mm × 10 mm × 2 mm and 40 mm × 10 mm × 2 mm. Resistance of ion gel in 10 kHz is 3.4 kΩ and 4.8 kΩ taking for 200 g and without loads, respectively. It is speculated that the electric resistance decreased with the shape change due to load application. Resistance of ion gel in 10 kHz is 12.3 kΩ, 5.86 kΩ and 3.48 kΩ at temperature of 40 ℃, 60 ℃ and 80 ℃, respectively. We confirmed the temperature dependency of impedance of the gel sample. The experimental results indicate that impedance was decreased with increase in frequency, load and temperature.

Currently, we are developing a human finger-modeled pressure and temperature sensor. Ion gel is shaped into human finger using a 3D printer. The LCR meter used for resistance measurement is made using Arduino. The technique shown in this study is expected to be applied to soft robot and robot hand.
Antibacterial Property of Cationic Hydrogels
Authors: Shibata Yuki , Kurokawa Takayuki , Aizawa Tomoyasu , Honglei Guo , Gong Jian Ping
Published: February 2020

【Introduction】

Physical and mechanical properties of a hydrogel, which is soft and has high water content, are similar to those of living tissues. Thus, a hydrogel attracts much interest as material for regenerative medicine and alternatives for human body. These properties of a hydrogel, however, also gives suitable environment for bacteria and mold. Therefore, hydrogel is easily contaminated by bacteria, which becomes a severe problem in their widespread applications. One possible way to solve this problem is use of antibacterial chemical agents. Hydrogels immersed in antibacterial agent aqueous solution can get antibacterial property temporally. However, such agent will gradually flow out and hydrogel lost antibacterial property as time goes on.

To overcome this problem, our strategy is to fix the antibacterial agents into the gel networks. It is known that cationic agent has good antibacterial property. In this time we synthesized a cationic hydrogel from (3-acrylamidopropyl)trimethyl-ammonium chloride and investigate antibacterial property of this hydrogel.

【Experiment】We prepared cationic hydrogel from (3-acrylamidopropyl)trimethyl-ammonium chloride, anionic hydrogel from sodium 2-acrylamido-2-methylpropanesulfonate, and neutral hydrogel from N,N-dimethylacrylamide. We also used agar gels as negative control. The prepared gels were soaked in saline to remove residual monomers for 1 week, and then put in saline including SYTO9 and propidium iodide for 1 day to perform live-dead imaging. E.coli was seeded on these samples, and the samples were put in an incubator(37°C) for 12 hour. After that, E.coli on samples were observed with a fluorescence microscope to calculate fraction of dead E.coli.

【Result】After 12 hours culturing, 86.3 % of E.coli on cationic hydrogel was dead whereas fraction of dead E.coli on the other gels was significantly smaller than that (Figure 1). This result suggests that cationic hydrogel has antibacterial property at least for E.coli.

Figure 1
(Keynote) Wearable Devices and Systems on Textiles for Biomedical Monitoring and Safety
Authors: Gray Bonnie L. , Chung Daehan
Published: February 2020

Great advances continue to be made in fields such wearable electronics, flexible electronics, functional polymers, and other soft materials. However, much of this research is field-specific, despite the enormous potential that the convergence of these research areas has to revolutionize personalized medicine, worker safety, and biomedical and environmental monitoring. We present our work in developing wearable devices and systems based on the convergence of multiple research areas in order to offer practical solutions for applications such as lighting and health monitors for safety vests; heart and perspiration monitors for athletic clothing; and other applications in real-time wearable bioelectric and biochemical monitoring.

Intense research into wearable electronics results in many innovative devices and systems, e.g.: flexible polymer printed circuit boards (PCBs); roll-to-roll foil and other printed devices; printing and weaving of textiles; and special geometries for flexible interconnect between rigid components. Our lab develops alternative methods, including conductive polymer nanocomposites and metal transfer processes for wearable bioelectric sensors. We present textile-based wearable devices and systems for electrocardiogram (ECG), tissue impedance, and pressure sensors. Unlike many other techniques, our technologies and materials are highly compatible with clothing-based textiles, and result in non-polarizable electrodes for improved frequency response.

Traditionally, biofluid-based biomedical sensors are fabricated in rigid substrates or flexible materials such as polydimethylsiloxane (PDMS) that are bonded to rigid substrates. Free-standing flexible devices are developed for, e.g., perspiration sensors; however, such processes typically require long fabrication times, equipment in a cleanroom facility, and difficulty with integration onto textiles. Other devices employ porous materials to deliver biofluids, e.g., perspiration, by capillary forces; however, such devices are limited in fluid collection and suffer from evaporation issues. To overcome these and other limitations of current devices, we present printing-based fabrication processes that employ screen printable ink for biomedical sensors for biofluid analysis. These devices and systems can be fabricated on textiles that can be laundered, facilitating rugged wearable devices and systems for biomedical and environmental monitoring.
Self-Toughening of Double Network Hydrogels By Using Bond Rupture-Induced Radical Polymerization
Authors: Namba Ryo , Matsuda Takahiro , Nakajima Tasuku , Nonoyama Takayuki , Kurokawa Takayuki , Gong Jian Ping
Published: February 2020

【Introduction】

Artificial materials are locally damaged and deteriorated when subjected to a long-term mechanical loading. Such local degradation of materials sometimes causes destruction of the material and severe accidents. Therefore, control of material deterioration is important for realizing a safe and secure society. On the other hand, in living tissues such as muscles, the damaged tissue structure is repaired and strengthened spontaneously through metabolism. In this study, we realize a system in which a new polymer network spontaneously polymerizes at a deteriorated site in hydrogels inspired from the metabolism of living tissues. The aim of this study is to create artificial materials that spontaneously repair degraded parts and further toughen themselves.

In order to achieve the above object "spontaneous polymerization of new polymer network at the deteriorated part", we focused on the Double Network (DN) gel developed in our laboratory. A DN gel exhibits high toughness despite 90% of water content. A DN gel is composed of two types of network with opposite physical nature, rigid and brittle first networks and soft and ductile second networks. Such contrasting double network structure make a DN gel so tough(1). In recent years, it was found that when mechanical load is applied to DN gel, covalent bonds of brittle first network are preferentially broken at loading part (degraded part), and a large amount of radical (mechanoradical) is generated. Utilizing this knowledge, in this study, by addition of a radical-polymerizable monomer/crosslinker to the DN gel, we aim to realize restoration and further toughening of the damaged DN gels through new polymer network synthesis from the radicals generated at the broken end of polymer chain (Fig. 1).

【Result】

A DN gel polymerized by a conventional method was immersed in a solution containing 2-acrylamido-2-methylpropane-sulfonate sodium salt (NaAMPS) as a monomer and N,N'-methylenbisacrylamide (MBAA) as a crosslinking agent. By applying tensile deformation to the DN gel, new polymer network was successfully synthesized at the stressed part. The tensile test of the stressed DN gels (Fig. 2) confirmed that both the fracture stress and the fracture strain greatly changed, and the work of extension, which shows the toughness of materials, was improved after tensile deformation.

【References】

1) J. P. Gong et al.,
Adv. Mater.,
2003, 15, 1155-1158

Figure 1