bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Self-Organization of Functional Hydrogel Microspheres at the Fluid Interface
Authors: Suzuki Daisuke 
Published: February 2020

The unique drying behavior of aqueous droplets that contain soft hydrogel microspheres (microgels) upon evaporation will be presented. The author’s group has previously reported that uniformly ordered thin films are obtained from drying poly(N-isopropyl acrylamide) microgel dispersions, in comparison with the ring-shaped deposits that are obtained from drying solid microsphere dispersions [1]. In this presentation, effects of the size, chemical structure, and crosslinking densities, i.e. “softness” of the microgels, substrates and so forth on the phenomenon were systematically investigated. For the macro- and microscopic observation of the drying behavior of various microgel dispersions, an optical microscope and a digital camera were used. The results suggested that the convection in the aqueous droplets plays an dominant role for the transportation of the microgels to the air/water interface. On the basis of these finding, a design guideline for the rapid formation of uniform thin films of microgels will be demonstrated [2]. In addition, recently further experimental results will be discussed.
Partially reproduced with permission from [2] Copyright (2018) American Chemical Society.
Reference
[1] K. Horigome et al. Langmuir
2012, 28, 12962−12970.
[2] M. Takizawa et al. Langmuir
2018, 34, 4515−4525.
4D Printed Soft Robot
Authors: Shiblee MD Nahin Islam , Ahmed Kumkum , Khosla Ajit , Furukawa Hidemitsu 
Published: February 2020

Hydrogels are capable of absorbing large amounts of liquid or biological fluids in three-dimensional polymeric networks. The properties of smart gels can be controlled or tuned by external stimuli such as heat, optics, solvent, and pH. Shape-memory gels (SMGs) are kind of smart material that have the ability to demonstrate reversible shape transformation induced by an external stimulus like in our present study: temperature sensitivity. Mechanically strong along with good flexibility and transparency, Poly(dimethyl acrylamide-co-stearyl acrylate) (DMMA-co-SA)-based SMGs [1] show thermoresponsive shape memory behavior above 40 °C. DMMA-co-SA SMGs have been fabricated by stereolithographic process using our customized 3D printer named as SWIM-ER. Using SWIM-ER we were able to print sample models like gel sheets, tubes, fingers etc. of SMGs that were transparent, flexible and strong. To successfully print SMG samples, we critically maintained all required conditions like polymerization inhibition, turbidity, light scattering etc. during printing and confirmed that printed SMGs exhibited similar properties like conventionally synthesized SMG. In this contribution, we presented 3D printed smart hydrogels that can morph according to the desired shapes. Utilizing this phenomenon we have made soft robots like soft gripper, smart capsule etc. Both the temperature responsiveness and swelling property of the hydrogels has been utilized as stimuli for shape transformation. Finally, we analyzed the limitation and potential of 3D printing process and discussed a possible approach for application of 4D printed SMGs in soft robotics.
Reference:
[1] Amano, Y; Hidema, R; Gong, J; Furukawa, H. Chem Lett.,41, 1029-1031 (2012)
Evaluation of Actuating Properties using Photoresponsive Polyimide Gel having Azobenzene Moiety
Authors: Matsumoto Masaya , Watanabe Toshiyuki , Karube Tamami , Isozaki Masatsugu , Misawa Kazuhiko 
Published: February 2020

The development of intelligent materials which can produce spontaneously different deformation under some external stimuli (such as temperature, electricity, light, magnetic field and so on) provides promising substances for materials chemistry and biomimetic engineering. Among them, azobenzene is attractive molecular transducer for light driven devices and optical switches due to the large reversible changes in molecular shape that occur upon isomerization. Light-driven applications are facilitated by the distinct absorption bands of the cis and trans isomers that allow for selective conversion and are robust even after multiple photocycles. Photoresponsive gels having azobenzene units in a rigid aromatic backbone are expected as a next generation actuator that offers direct energy conversion from light to macroscopic work. Since it is not necessary electric wiring, possible to be operated remotely with light. And its operation principle is based on the movement of molecular scale, so it could be miniaturized.
In this study, we synthesized photoresponsive polyimide (PI) gels which are hardly hydrolyzed and decomposed as compared with precursor photoresponsive poly (amide acid) (PAA) gels. Conventional polyimide gels obtained by crosslinking bifunctional oligomers having azobenzene moiety with tetrafunctional amine showed no reversible photoresponsiveness. However, by using N,N’-bis(3,5-diaminobenzoyl)-4,4’-diaminoazobenzene (BDA-Azo) as a tetrafunctional crosslinking agent which azobenzene is introduced, a centimeter-long cantilever made up of the photoresponsive PI gel exhibited reversible bending motions which were faster than the precursor PAA gel upon blue (402 nm) and visible light (532 nm) irradiation. Therefore, in order to elucidate the influence of chemical structure on bending behavior, we investigated various physical properties of the novel PI gel composed of BDA-Azo, conventional PI gel and their precursor by using UV-vis spectrum measurement, Raman scattering measurement, etc. and discussed relationships between photoisomerization and bending behavior.
Formation of Tough and Deformable Films through Evaporating Dispersions of Elastomer Microspheres By Crosslinked with Rotaxane
Authors: Hiroshige Seina , Kureha Takuma , Sawada Jun , Aoki Daisuke , Takata Toshikazu , Suzuki Daisuke 
Published: February 2020

Downsizing polymer materials (<~10 micrometers) to the colloidal scale can be dispersed in the solvent and showed distinctly different behavior from the corresponding bulk materials. One of the most useful application of colloidal dispersions is that they are injectable, which significantly simplifies method of bulk materials. Compared to rigid microspheres based on polystyrene or silica, soft and deformable elastomer microspheres have been used to create colorless transparent films through solvent evaporation. In general, to obtain tough microsphere films, many additives are required, and/or post-polymerization modification is necessary. In this study, we synthesized elastomer microspheres cross-linked with rotaxane, and succeeded in getting tough films by simply evaporating water [1]. To obtain colloidal microspheres with flexible crosslinkers, a rotaxane crosslinker (RC), consisting of a crown ether wheel and an axle with one vinyl group per component. We selected mini-emulsion polymerization, in which an oil monomer droplet is polymerized to become a polymer microsphere, to sufficiently trap the RC within the microspheres because the RC hardly dissolves in water but can be dissolved in organic solvents or oil-monomers. Films were generated by depositing an elastomer microsphere dispersion on a silicon rubber sheet, followed by drying at room temperature and annealing effect. Tensile tests were performed at 25 °C at an elongation rate of 10 mm/min.
The BM and BM-D0.05 films, in which the microspheres were crosslinked only physically and by conventional crosslinkers, were brittle because the chain entanglement between the microspheres was able to slip easily upon elongation, and the fracture energies (En
) of these films were <10 MJm-3. In contrast, BM-R0.05 film, where the microspheres were crosslinked by RC, reveal increased fracture stress and fracture strain (Figure 1). It suggested that the stress relaxation in each elastomer microsphere, originating from the flexibility of the crosslinking points, affected on the mechanical properties of the BM-R0.05 film, even though the post crosslinking reaction between the microspheres was not performed. The result of this study should find the advanced applications for such as in the areas of medicine and cosmetics, in which the minimization of impurities is desirable. Furthermore, the effect of film preparation condition will be discussed. Partially reproduced with permission from [1] Copyright (2018) John Wiley and Sons.
Reference
[1] S. Hiroshige, T. Kureha, D. Aoki, J. Sawada, D. Aoki, T. Takata, D. Suzuki, Chemistry - A European Journal,
2017, 23, 8405 – 8408.

Figure 1
Hydrogel Filled with Monodisperse Mesoporous Silica
Authors: Miyamoto Nobuyoshih , Ishii Hiroki , Koga Tomoyo 
Published: February 2020

Mesoporous silica materials synthesized by condensation of silica species in the presence of structure directing templateshave been widely investigatedso far.The mesopores with precisely controllable size, ordering, topology, and very large surface area per weight are suitable for many applications such as adsorbent and catalyst supports. These materials would also serve as novel fillers for polymer materials; with addition of only small amount of the fillers, very effective physical interactions of the polymer chains on the pore surfaces as well as topological confinement of the polymer chains piercing through the mesopores are expected, which would allow significant enhancement in mechanical properties of the materials. In this study, we demonstrate the synthesis poly(N-isopropylacrylamide) gel doped with mesoporous silica particles (mMPS) that have very small size and narrow particle size distribution. The composite gel shows largely improved mechanical property.
The mesoporous silica (MPS) particles were synthesized from an aqueous mixture of triethanolamine, cetyltrimethylammonium bromide, and tetraethoxysilene, according to the method reported in the literature1. The MPS colloid was added with monomer (N-isopropylacrylamide), chemicalcrosslinker (N,N'-methylenebisacrylamide) and photoinitiator (2-hydroxy-2-methylpropiophenon). The solution was sealed in a cell and irradiated with ultraviolet light to obtain composite gel by photopolymerization.
In the transmission electron microscope images of the MPS, the particles with the diameter of around 20 nm were observed. The surface of the particles were not smooth but rough , indicating the presence of mesopores. Dynamic light scattering showed that the MPS have average diameter of MPS is 21.8 nm with the standard deviation of 5.3nm.
The obtained gels were perfectly transparent, indicating no aggregation of the MPS in the gel. In the tensile stretching test, the gel doped with 0.0002 wt% showed the breaking strain of 305% and breaking stress of 36 kPa. These values are much better compared to the gel without MPS that showed the breaking strain of 56% and breaking stress of 11 kPa. It is notable that the elastic modulus of the gel is not so much different. The mechanical reinforcement is explained by thhe topological crosslink by the mesopores as well as physical crosslink by interaction between the polymer chains and the silica surface.

Reference

1. Chihiro,U.et al. Chem. Commun. 2009, 5094.
(Invited) Wettability Switching of Diamine Polymer Coatings by CO2 Capture
Authors: Suga Takeo , Sahashi Yusuke , Nishide Hiroyuki 
Published: February 2020

Aliphatic and aromatic amine derivatives have attracted much attention as absorbents to capture waste CO2 in the industrial processes. The formed carbamic acids release CO2 and are recovered reversibly. Here we design various diamine derivatives to capture/bind CO2 more strongly, and incorporated into the polymer coating for anti-fouling applications.
Aqueous solutions of various diamine derivatives (primary to tertiary amines with different spacer lengths) were treated with CO2, and in-situ NMR spectra estimated the ratio of zwitterion to dication species. CO2-responsive diamine polymer was synthesized and added to epoxy thermosets. Thermally cured coating exhibited surface property change by CO2 addition under water. Not only bubbling CO2, but also atmospheric CO2 concentration (300 ppm) allowed surface property change. Contact angle measurement indicated drastic decrease in interfacial tension between water and surface. Swelling behavior of the crosslinked polymer layer will be discussed by In-situ AFM and neutron reflectivity.
(Invited) Printed Flexible Pressure Sensor Driven by OTFT Array
Authors: Nishi Shinichi 
Published: February 2020

We have constructed an all printed electronics device　manufacturing line and fabricated an organic TFT array on a flexible film substrate. In the automated and continuously operated manufacturing line, we used the reverse offset printer for electrode pattern, digital inkjet printer for organic semiconductor layer, slit-die coater for insulator layer, and gravure offset printer for pixel electrode, specified printer for pressure sensitive layer. The printed pattern with high resolution and high accuracy can be obtained on a flexible film, not only PI, PEN but PET film substrate in low process temperature.
The all-printed organic TFT array back-plane is applied to the flexible and light-weight pressure sensor which is driven in active matrix mode. As an example, we demonstrated the compact cylindrical pressure sensor with bare-chip driver ICs at international nanotechnology exhibition in 2018 as shown in lower photo. By taking an advantage of the flexible lightweight and high resolution characteristics of sensors, we are continuing some kinds of field testing in field of healthcare-related applications of rehabilitation and nursing care support and also shelf management system at a convenient store. Furthermore we are challenging the development of robot skin which has sensors as sensitive as human touch.
Compact cylindrical pressure sensor demonstrated at international nanotechnology exhibition in 2018.

Figure 1
Immobilization of Glucose Dehydrogenase on Epoxy Group-Modified MgO-Templated Porous Carbon Electrode for Improvement of Biofuel Cell Stability
Authors: Kato Takanao , Hoshi Yoshinao , Shitanda Isao , Itagaki Masayuki 
Published: February 2020

Enzymatic glucose/O2 biofuel cells (BFCs) are energy conversion systems in which enzymes oxidize glucose at a bioanode and reduce oxygen at a biocathode. These enzymes are highly safe toward humans, and highly selective for substrates, without leaving toxic residues at room temperature and neutral pH conditions.
There are many recent studies on self-powered biosensing systems based on BFCs. We have reported that the output power is dramatically improved by using MgO-templated porous carbon (MgOC) for electrodes of biofuel cells [1-2]. MgOC has suitable mesopores for entrapping an enzyme whose redox center can approach the carbon surface with high probability. In addition, the long-term stability may be improved because the ellusion of the enzyme was suppressed by entrapping the enzyme in the mesopore. In this study, we newly performed chemical immobilization of glucose dehydrogenase (GDH) on the MgOC surface to improve the long-term stability further. A MgOC poweder having an average pore diameter of 100 nm was purchased from by Toyo Carbon Co. Ltd. The epoxy group-modified MgOC was synthesized by graft polymerization technique. The epoxy group-modified MgOC was coated on a glassy carbon electrode, and then 1,2-naphthoquinone(1,2-NQ) was modified as a mediator and glucose dehydrogenase (FAD-GDH) was modified as an enzyme to be prepared an enzyme electrode. Cyclic voltammetry and chronoamperometry of the enzyme electrode were measured in a 3-electrode system in 1.0 M phosphate buffer solution (PBS) containing 100 mM glucose. Stability of the enzyme electrode was evaluated by performing cyclic voltammetry in multiple cycle measurement.
Figure 1 shows the cyclic voltammogram of enzyme electrode. Catalytic oxidation current was observed at a nobler potential than -0.1 V. Also, the maximum current value in the 1st cycle was 11.2 mA cm-2. The peak current value of the present enzyme electrode was almost the same compared with that of an enzyme electrode in which epoxy group-unmodified MgOC was used as the electrode material. The results indicated that the enzymatic activity of FAD-GDH was not changed by the chemical immobilization.
Figure 2 shows the relation between the number of cycles and normalized current density at 0.3 V.
When the MgOC was modified by epoxy group, the current value of 90% was retained after 25 cycles, whereas it was 52% in the case of unmodified MgOC. From the above results, Elution of FAD-GDH could be suppressed by using epoxy group-modified MgOC because the amino group of the enzyme shell and the epoxy group on the carbon surface are bonded successfully.

References

[1] S. Tsujimura et al., Electrochemistry 83 (2015) 372.
[2] I. Shitanda et al., J. Power Sources 360 (2017) 516.

Acknowledgement

This work was supported by JST-ASTEP Grant Number AS272S004a and JSPS KAKENHI Grant Number 17H02162.

Figure 1
(Invited) Paper-Based Printable Lactate/Glucose Biofuel Cell Toward Self-Powered Biosensor
Authors: Shitanda Isao , Tsujimura Seiya , Morigayama Yukiya , Mikawa Tsutomu , Hoshi Yoshinao , Itagaki Masayuki , Matsui Hiroyuki , Tokito Shizuo 
Published: February 2020

A paper-based biofuel cell (PBFC) which is based on printing technologies, are attracting increasing attention as new energy harvesting systems for sensor tags, wearable biomedical devices, and small electrical devices [1-3]. The PBFC is also useful for a self-powered biosensing system [4-5] In this talk, I introduce a high power lactate/glucose PBFC, which was created by series and parallel array structures. The single PBFC was composed of a bioanode and a biocathode that were based on porous carbon electrodes constructed using porous carbon inks. The porous carbon material, namely MgO-templated carbon, has suitable mesopores for entrapping an enzyme whose redox center can approach the carbon surface with high probability. In addition, the long-term stability may be improved because the ellusion of the enzyme was suppressed by entrapping the enzyme in the mesopore. A 6-series/6-parallel lactate PBFC array, which is based on a new array structure, exhibited an output power of about 4.3 mW, and an open circuit voltage of about 3.6 V. For example, the present PBFC was able to light an LED directly, without the requirement of a step-up circuit board and we achieve a wireless transmitting of the information of lactate concentration with a smart phone. In the present study, I will show you our resent results about printable lactate/glucose self-powered biosensors.
Acknowledgement
This work was supported by JST-ASTEP Grant Number AS272S004a and JSPS KAKENHI Grant Number 17H02162.
References

C. W. N. Villarrubia, F. Soavi, C. Santoro, C. Arbizzani, A. Serov, S. Rojas-Carbonell, G. Gupta and P. Atanassov, Biosens. Bioelectron., 2016, 86, 459.

M. J. González-Guerrero, F. J. del Campo, J. P. Esquivel, F. Giroud, S. D. Minteer and N. Sabaté, J. Power Sources, 2016, 326, 410.

S. Li, Y. Wang, S. Ge, J. Yu and M. Yan, Biosens. Bioelectron., 2015, 71, 18.

I. Shitanda, M. Momiyama, N. Watanabe, T. Tanaka, S. Tsujimura, Y. Hoshi, M. Itagaki, ChemElectroChem, 2017, 4, 2460.

I. Shitanda, S. Nohara, Y. Hoshi, M. Itagaki, S. Tsujimura, J. Power Sources, 2017,
(Keynote) Dimensional Change of Oriented Polymers upon Heating
Authors: Kikutani Takeshi 
Published: February 2020

Molecular orientation can be incorporated to the polymeric materials through either stretching in a solid state or elongation in a molten state. When a polymer has molecular orientation in a glassy state, shrinkage may proceed when temperature is increased above its glass transition temperature. Degree of shrinkage may vary depending on the temperature reached and the degree of molecular orientation.
In the case of crystalline polymers, however, shrinkage may be suppressed because of the occurrence of crystallization prior to the shrinkage. It should be noted that the crystallization rate can be accelerated significantly with the increase of molecular orientation. Accordingly, there can be a critical degree of molecular orientation; below which orientation relaxation proceeds upon heating, whereas above which spontaneous orientation enhancement caused by crystallization proceeds upon heating. In some cases, even the spontaneous elongation of materials takes place along with the progress of crystallization.
On the other hand, it is well known that the dynamics of polymeric materials is characterized by the wide range of relaxation time. This means that the state of molecular orientation can be manipulated through the combination of deformation/flow history and temperature history. Dimensional change of oriented polymeric materials upon heating is mainly governed by the oriented structure of relatively long relaxation time such as network structure of molecular entanglement. Based on this concept, we could prepare fibers which showed no birefringence but exhibited significant shrinkage with the increase of temperature. This is possible because birefringence merely reflects the degree of orientation of relatively short segments, i.e. short relaxation time, in the polymer chain.
Concept of manipulating the oriented structure of wide range of relaxation period leads to the idea of controlling the state of molecular entanglement. Based on this concept, we speculated that the polymeric materials of high strength and high toughness can be prepared if the material has rather homogeneous state of molecular entanglement, i.e. narrow distribution of molecular weight between adjacent entanglement points.
As-spun poly(ethylene terephthalate) (PET) fibers with rather homogeneous state of molecular entanglement was prepared through the control of melt spinning process. Applying the drawing and annealing processes to such as-spun fibers, high-strength PET fibers were prepared. To verify the applicability of the concept of homogeneous state of molecular entanglement, PET fibers prepared under various processing conditions were analyzed using the laser Raman spectroscopy. It was found that the narrow distribution of internal stress field and limited widening of such distribution upon applying the tensile stress to the fibers are the key factors for realizing the high-strength and high-toughness.