bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Dynamics Simulations of Ionic Diffusion in PEO-LiTFSI Polymer Electrolyte: Effect of Temperature, Molecular Weight, and Ionic Concentration
Authors: Merinov Boris V , Brooks Daniel J , Goddard William A
Published: February 2020

Polymer electrolytes are promising materials for development of the next generation of energy storage devices, including lithium-ion polymer batteries, due to their exceptional chemical and mechanical stability, high energy density and long lifetimes. Understanding the ionic diffusion mechanism in polymer electrolytes is critical to the development of advanced lithium-ion batteries. A molecular dynamics-based characterization of structures and diffusion in poly(ethylene oxide) (PEO) with lithium and bis(trifluoromethy-sulfonyl-imide) (TFSI) ions imbedded into the PEO structure have been performed across a range of temperatures, molecular weights and ion concentrations, with relative ionic diffusion coefficients shown to be in good agreement with experimental measurements. To determine details of the atomistic diffusion mechanism, the chain coordination of Li atoms, polymer motion, and temperature dependences of the intrachain and interchain diffusion contributions into the total ionic diffusion coefficients on ionic concentration and molecular weight were analyzed. We find that the most diffusive Li atoms exhibit frequent interchain hopping, whereas the least diffusive Li atoms rather oscillate or “shift” coordination between two or more polymer chains. These shifts may actually reduce the segmental motion of the PEO-LiTFSI polymer, which is important for the fast lithium-ion diffusion. Good agreement between experiment and theory validates the approach and methodology used in this study and its further applications for predicting the structure and ionic conductivity of new advanced polymer materials for a new generation of electrochemical devices.

Acknowledgement

This work was supported by Bosch Energy Research Network Grant No. 13.01.CC11.
Study of Highly Active and Durable Bifunctional Catalyst for Rechargeable Zinc-Air Battery
Authors: Lee Chun-I , Jung Shiauh-Ping , Chiu Sheng-Cheng , Yang Chang Chung
Published: February 2020

Rechargeable zinc-air batteries, which are cost-effective, environmental compatibility, and have high energy density, are promising energy storage devices for renewable energy and power sources for electric transportation. However, the critical issues that impede the commercialization of rechargeable zinc–air batteries are limited charge and discharge cycles and the sluggish kinetics of oxygen reduction and evolution reactions, which affect the round trip efficiency. Over the past years, numerous efforts have been devoted to develop earth-abundant materials as bifunctional catalysts towards both OER and ORR. But a suitable bifunctional catalyst has not really been found yet. Therefore, the rechargeable zinc–air battery with cobalt oxide nanoparticles as a bifunctional catalyst are investigated. The result shows that the rechargeable zinc-air batteries in a two-electrode configuration exhibited a small charge–discharge voltage polarization of ~0.70 V at 5 mA cm−2, high reversibility and stability during battery discharge, charge, and cycling processes.
(Invited) A Controlled Internal Short-Circuit Method for Li-Ion Safety Assessment
Authors: Ma Chengsong
Published: February 2020

Saft has developed a method which more accurately simulates internal short than other methods via an embedded heater. The advantage of this method is that it can be triggered at any point or operating condition. Cells can be triggered at any position in a module. It is robust and relatively easy to fabricate. It is an aggressive testing method, but so far it has been proven to be the most convenient and reproducible method to estimate the effects caused by short-circuit. It has been tested in designed environment with the products at desired SOC and the results are reliable, reproducible and informative. The method serves as gold standard in Saft to evaluate the safety of our products against internal short-circuit and it is widely used to validate Saft’s design of different cell, module and battery products.
(Invited) Molecular Dynamics Simulations of Solid Electrolytes for Li-Ion Nanobatteries
Authors: Seminario Jorge M. , Ponce Victor H , Galvez-Aranda Diego Eduardo , Vicharra Cristhian , Selis Luis , Franco-Gallo Franz , Gamero T Milenka
Published: February 2020

Silicon and metal lithium anodes are excellent alternatives for Li-ion batteries; cathodes based on sulfur are also great alternatives as well as new spinel structures. On the other hand, swelling of the anode upon lithiation causes cracks on the anode protective solid electrolyte interphase (SEI), creating channels for the electrolyte to enter and disturb the anode, leading to capacity fading, and short- or open-circuit failures; among them, the growth of lithium dendrites is one of the most important to take care due to safety issues. One possible solution to this, and perhaps the other problems, is the use of solid electrolytes. The extremely slow drift velocity of the Li-ions in a typical commercial Li-ion battery, makes the growth of a dendrite take a few hours; however, once a Li-ion arrives at an active site of the anode, it takes an extremely short time of ~1 ps to react. This large difference in time-scales allows us to perform molecular dynamics simulation of ions at much larger drift velocities, such that we can have valuable results in reasonable computational times. Therefore, we study the properties of the above new materials for electrodes and electrolytes as parts of a full nanobattery. We will show details of the electrochemistry going on at those interfaces such as the formation of a SEIs at the anode side, the inflation due to lithiation, the stress to number of bonds in the SEI relation, cracking onset relations, and the amorphization mechanism, among others.1-4

REFERENCES

Selis, L. A.; Seminario, J. M., Dendrite Formation in Anodes of LIB. RSC - Advances In Press.

Galvez-Aranda, D. E.; Seminario, J. M., Simulations of a LiF Solid Electrolyte Interphase Cracking on Silicon Anodes Using Molecular Dynamics. J. Electrochem. Soc. 2018, 165, A717-A730.

Ponce, V.; Galvez-Aranda, D. E.; Seminario, J. M., Analysis of a Li-Ion Nanobattery with Graphite Anode Using Molecular Dynamics Simulations. J. Phys. Chem. C 2017, 121, 12959–12971.

Galvez-Aranda, D. E.; Ponce, V.; Seminario, J. M., Molecular Dynamics Simulations of the First Charge of a Li-Ion—Si-Anode Nanobattery. J. Mol. Model. 2017, 23, 120.
Morphology and Electronic Signature of Li2s Growth on Graphene for New Nanostructured Cathodes for Li-S Batteries
Authors: Longo Roberto , Balbuena Perla B
Published: February 2020

Lithium-sulfur (Li-S) batteries have been the subject of intensive research during the past decade as a next-generation conversion battery chemistry, owing to their higher theoretical gravimetric energy density (1672 mAh·g-1), as compared to the traditional intercalation Li-ion batteries of current use in portable electronics and hybrid electric vehicles. Although much progress has been made in the attempt to overcome the inherent problems associated with the use of insulating active materials -both sulfur and the final Li2S discharge product- many questions remain regarding the use of nanostructured sulfur-carbon cathodes and the formation of Li2S during cycling. By using first-principles calculations, here we present the early stages of Li2S growth on a typical carbon substrate, such as graphene, in order to shed light on the morphology and electronic properties of this insulating material that can lead to voltage decay, capacity fade and ultimately the stalling of the Li-S battery. Our findings provide conceptual guidance in the experimental search for the mechanisms driving the voltage and capacity fading of Li-S batteries upon growth of such reaction products, in an attempt to solve the structural instability and, therefore, help in the design of new nanostructured sulfur-carbon cathodes for Li-S batteries.
The Influence of State-of-Charge on Ageing in Commercial Li-Ion Pouch Cells
Authors: Wikner Evelina , Thiringer Torbjörn , Scheers Johan
Published: February 2020

Vehicle manufacturers are increasingly electrifying their vehicles using Lithium-ion batteries (LiBs) as the energy storage unit. With a very high battery cost, the requirements on LiB life and performance are necessarily stringent and much effort goes into understanding how these properties are influenced by the conditions of use. For electric vehicles a large State-of-Charge (SOC) operation window has to be balanced with the lifetime expectancy. Being able to correlate load cycles to a specific type of ageing is crucial to understand how to better utilize the LiBs - improving the accuracy of lifetime predictions and optimizing the performance/lifetime balance in the vehicle.

A physics-based ageing model of a commercial Li-ion pouch cell with a graphite anode and a blended LMO/NMC cathode has been developed. The model is based on the Newman theory [1], as implemented in COMSOL [2-6], and is a direct continuation of the work in [6]. The growth of a solid electrolyte interphase (SEI), resulting in increased resistance and capacity loss, constitutes the main ageing mechanisms of the model, which has been tuned with experimental test data as input. The SEI growth has also been linked to a change in active material porosity and thereby a reduced electrolyte volume in the electrode. The resulting effect on the cell resistance and capacity during various test conditions is determined, and the impact from the different ageing parameters evaluated.

The experimental tests used synthetic load cycles for various C-rates, at different Depth of Discharge (DOD) and at different SOC. The results show an expected increased ageing with C-rate, but more surprising is the ageing patterns seen for small DOD, at various SOC intervals, which do not follow the trend observed for LiBs with LFP cathodes [7]. The LiB here degrade most strongly at high SOC (> 60%), in accordance with previous research, while at SOC < 30% ageing is impressively slow. The slow capacity degradation of the cells in SOC intervals < 30% make their cycle lifetime more than 3x longer compared to the cells run at high SOC. The developed ageing model can successfully capture the difference in capacity loss due to larger SEI growth at high SOC.

References:

[1] M. Doyle, T.F. Fuller, J. Newman, J. Electrochem. Soc. 140 (1993) 1526-1533.

[2] H. Ekström, G. Lindbergh, J. Electrochem. Soc. 162 (2015) A1003-A1007.

[3] P. Ramadass, B. Haran, P.M. Gomadam, R. White, B.N. Popov, J. Electrochem. Soc. 151 (2004) A196-A203.

[4] R. Darling, J. Newman, J. Electrochem. Soc. 145 (1998) 990-998.

[5] S. Santhanagopalan, Q. Guo, P. Ramadass, R. E. White, J. Power Sources 156 (2006) 620-628.

[6] E. Wikner, Lithium ion Battery Aging: Battery Lifetime Testing and Physics-based Modeling for Electric Vehicle Applications, Chalmers University of Technology, Göteborg, 2017.

[7] J. Groot, State-of-Health Estimation of Li-ion Batteries: Ageing Models, Chalmers University of Technology, Göteborg, 2014.
Charge Transport and Practical Applications of All-Carbon Molecular Electronic Devices
Authors: Supur Mustafa , Najarian Amin , Bergren Adam Johan , McCreery Richard
Published: February 2020

Molecular electronic junctions can be made by covalently bonding aromatic molecules and graphene ribbons to a flat, sp2 hybridized carbon electrode followed by a “top contact” of electron-beam deposited carbon. The entire active region of the structure consists of carbon and hydrogen, and electronic properties range from insulators to efficient conductors, with excellent lifetime and tolerance to temperature excursions. 1-3 Of particular interest is a carbon/graphene/carbon device containing 5-carbon wide graphene ribbons, which avoids torsional disorder common to aromatic molecular components (shown schematically below, left). The graphene devices have the highest molecular conductance reported to date for large-area molecular junctions, and is stable for at least five million current/voltage cycles to ±4 A/cm2. 4 An application of all-carbon molecular tunnel junctions in electronic music will be described, which resulted in the first known commercial product involving molecular electronics (below, right). 5

(1) Morteza Najarian, A.; Bayat, A.; McCreery, R. L.; Orbital Control of Photocurrents in Large Area All-Carbon Molecular Junctions; Journal of the American Chemical Society
2018, 140, 1900.

(2) Supur, M.; Smith, S. R.; McCreery, R. L.; Characterization of Growth Patterns of Nanoscale Organic Films on Carbon Electrodes by Surface Enhanced Raman Spectroscopy; Analytical Chemistry
2017, 89, 6463.

(3) Morteza Najarian, A.; McCreery, R. L.; Structure Controlled Long-Range Sequential Tunneling in Carbon-Based Molecular Junctions; ACS Nano
2017, 11, 3542.

(4) Supur, M.; Van Dyck, C.; Bergren, A. J.; McCreery, R. L.; Bottom-up, Robust Graphene Ribbon Electronics in All-Carbon Molecular Junctions; ACS Applied Materials & Interfaces
2018, 10, 6090.

(5) Bergren, A. J.; Zeer-Wanklyn, L.; Semple, M.; Pekas, N.; Szeto, B.; McCreery, R. L.; Musical molecules: the molecular junction as an active component in audio distortion circuits; Journal of Physics: Condensed Matter
2016, 28, 094011.

Figure 1
(Invited) Hybrid Plasmons in Graphene-Graphene Heterostructure
Authors: Rotkin Slava V.
Published: February 2020

One of most distinct features of two-dimensional layered materials (2DLMs), for example, graphene, is the existence of strong polaritonic modes. Plasmon-polaritons of 2D graphene are similar to other 2D plasmonic modes which are well studied. However, due to ease of van der Waals stacking, 2DLMs also allow formation of vertical heterostructures with multiple layers. The talk will touch upon hybrid plasmon modes in these nanoscale structures.
Toward the Chemical Isolation of Larger-Size Empty-Cage Fullerenes
Authors: Stevenson Steven , Koenig Ryan
Published: February 2020

A plethora of literature exists for C60 and C70. Isolated in gram quantities since the early 1990s, these empty-cage fullerenes are well-studied due to their (1) high abundance in carbon soot extracts and (2) ease of separation. Depending on the method of synthesis (e.g., electric-arc), C60 and C70 typically comprise 95-98% of the soluble fullerene extract. The remaining 2-5% represents the higher fullerenes, e.g., C76 - C140 and beyond. How does one isolate these higher cage fullerenes given their extremely low abundance? Great question - which will be addressed.

Our goal is developing a new separation method to chemically isolate these higher fullerenes. An inherent advantage to chemical methods is the removal of structural isomers, which present co-elution challenges with HPLC alone. In this presentation, we discuss the attractiveness of being able to remove more reactive fullerenes to greatly simplify samples. A successful purification strategy for isolating higher fullerenes would make macroscopic quantities available for the first time.
Electrochemical Intercalation of AP-CVD Grown Few-Layer and Multi-Layer Graphene
Authors: Accogli Alessandra , Gibertini Eugenio , Pedrazzetti Lorenzo , Panzeri Gabriele , Lucotti Andrea , Magagnin Luca
Published: February 2020

First studies on intercalation of graphite date back to the first half of the XX century. At first, the ability of graphite to spontaneously form intercalation compound (GIC) by the soaking in strong acids was studied. Only later, GIC were obtained by electrochemical route, highlighting the mechanism of formation of GIC in extremely ordered layered structure as HOPG [1,2]. Anodic electrochemical intercalation is typically performed in acidic aqueous solution, forming GIC by the insertion of anions as ClO4-, HSO4- and NO3- [3]. Anodic electrochemical intercalation is nowadays useful to obtain high quality Graphene Oxide (GO) thorough an easy and green route [4]. Studies on the formation of GIC by cathodic polarization opened to the understanding and exploitation of the reversible intercalation of alkali ions (Li+, Na+) that found the suitable application in Li battery technology [5]. However, up to now, studies have concentrated mainly on the electrochemical formation of GIC HOPG, but very few have investigated the GIC formation in nanoscaled graphitic material as graphene [6]. In this work, we provide a comprehensive understanding of the GIC formation by electrochemical route in few-layer graphene grown through atmospheric pressure chemical vapor deposition (ACVD) on metallic substrates. Anodic electrochemical intercalation of few layer graphene in acidic, organic-based and aqueous-based media has been investigated. A deeper understanding of intercalation and doping phenomena of few layer graphene has been performed in situ through Raman spectroscopy measurements. Preliminary results on cathodic intercalation of few layer graphene in aqueous and organic media will be also discussed.

References

[1] H. Thiele, Trans. Faraday Soc., 1938,34, 1033-1039

[2] F.Beck, H.Junge, H.Krohn, Electrochemical Acta, 26 (7), 1981, 799-809

[3] D.C. Alsmeyer, R. L. McCreery, Anal. Chem., 1992, 64 (14), 1528–153

[4] K. Parvez, Z. Wo, R. Li, X. Liu, R. Graf, X. Feng, K. Müllen J. Am. Chem. Soc., 2014, 136 (16), 6083–6091

[5] S.Basu, C.Zeller, P.J.Flanders, C.D.Fuerst, W.D.Johnson, J.E.Fischer, Materials Science and Engineering, 1979, 38 (3), 275-283

[6] E. Pollak, B. Geng, K. Jeon, I.T. Lucas, T. J, Richardson, F. Wang, R. Kostecki, Nano Lett., 2010, 10 (9), pp 3386–3388.
Synthesis of Graphene By Electrochemical Exfoliation of Graphite in Aqueous Solution
Authors: Roberts E.P.L. , Sharif Farbod , Holmes Stuart , Perez-page Maria
Published: February 2020

Of the various methods available for the preparation of graphene, thermal exfoliation via the modified Hummer's method provides a low cost, scalable process. However the process has several drawbacks: high temperature processing is required, the quality of the graphene is relatively poor, and chemical reduction is required to reduce the graphene oxide generated by the thermal exfoliation process. Electrochemical exfoliation can be carried out under ambient conditions, and by controlling the exfoliation conditions the properties of the graphene produced can be tuned. In this study we evaluate electrochemical exfoliation in aqueous solution, and in particular investigate the influence of the solution composition on the properties of the synthesized graphene. We find that the salt used influences the quality of the graphene, the surface functionality, thermal stability and the degree of oxidation. Graphene can be produced with a yield of order 65%, with a particle size of order 1 to 10 μm, a high proportion of single layer graphene, and a good electrical conductivity without the need for chemical reduction. Doping of heteroatoms such as nitrogen can be achieved by selecting a suitable salt solution. Furthermore, with a suitable salt a graphene with exceptional thermal stability can be prepared, with minimal mass loss up to 750°C and maintaining good conductivity after prolonged exposure to high temperature.
Preparation and Evaluation of Pt-Ru/CNTs Catalysts for Direct Methanol Fuel Cell
Authors: Tavakoli Mehrabadi Bahareh Alsadat , Regalbuto John R. , Weidner John W. , Monnier John R.
Published: February 2020

The most widely used electro-catalyst material in direct methanol fuel cell (DMFCs) are Pt-Ru bimetallic electro-catalysts, which show the best performance among other bimetallic catalysts. Many methods exist to prepare catalysts with bimetallic surfaces, and the properties and performance of these catalysts vary widely. Previous studies have shown that combining strong electrostatic adsorption (SEA) and electroless deposition (ED) methods can increase the surface area of the Pt particles by lowering the particle sizes of the bimetallic particles [1]; however, decreasing particle sizes can result in other problems such as thermal stability. Therefore, new routes for development of highly active and stable catalyst supports have become important to study. Among the different forms of carbon support, carbon nanotubes (CNTs) are especially known for their crystallinity which not only imparts structural uniformity and high electrical conductivity, but also assures stability of the nanomaterials deposited on the support. In addition, they fulfill the properties of high surface area, high thermal conductivities, extraordinary strength, and resilience to an acidic environment, all of which can prove highly important for improving the performance of a fuel cell catalyst.

In this work we have investigated the effect of CNTs support for the methanol electro-oxidation reaction. The combination of SEA and ED methods have been used for deposition of Pt-Ru bimetallic catalysts on CNTs and to predict the effect of support on DMFC performance. The materials synthesized will be characterized by X-ray diffraction (XRD) spectroscopy for crystal structure and energy dispersive spectroscopy (EDS) will be employed to examine elemental analysis and distribution. To observe surface morphology HRTEM images will be used, and BET surface areas and pore volume measurements will be carried out to evaluate porosity and pore size distributions.

References

Tengco, J.M.M., et al., Synthesis and Electrochemical Evaluation of Carbon Supported Pt-Co Bimetallic Catalysts Prepared by Electroless Deposition and Modified Charge Enhanced Dry Impregnation. Catalysts, 2016. 6(6).
(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.
(Invited) Dynamic Evolution for Soft Matter Robot: Integrated Fabrication of Geometric and Motion of Gel-like Robot with Embedded Virtual Link Structure
Authors: Ogawa Jun
Published: February 2020

The current 3D printing technology can easily fabricate a body of soft robot composed of various materials. The body of these soft robots has many advantages from the viewpoint of physical interference due to contact using the soft material. Soft robot research in the field of robotics has been reporting a control method to efficiently drive a mechanical structure capable of high freedom movement by combining rigid mechanical parts. However, to transfer these technologies to soft matter science, we are still facing on many problems. As one of the problems, in the academic field of chemistry and robotics, the design concept of soft robot material, geometric structure and movement is not unified. In particular, heterogeneous hybrid materials and link mechanisms are technically separated and discussed. In this study, from the viewpoint of informatics, we integrate the technologies of both by embedding a virtual link structure in the body of soft material. In addition it is an object to create a numerical simulation model for implementing geometry design and physical computation of the soft robot to gradually and simultaneously adapt to external environment. This is because geometry and kinematics for soft robots are not yet established. We have adopted a voxel-based physics calculation library for simulation model. It is open source called Voxelyze. The geometric shape of the soft robot's physical model is created by neural evolution which develops optimization by neural network and evolutionary calculation. When the optimized neural network inputs the coordinate information of the three-dimensional design space, it outputs a three-dimensional physical model composed of voxels of dissimilar materials. Each constitution voxel of the model includes those having an actuator function. It is dominated by the link structure between the corresponding voxels having this actuator function. Our simulation model enables 3D modeling considering the motion of robot which needs time information. In addition, we can find guidelines for simultaneously acquiring structural stability and task performance of soft robot.
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
(Invited) Phase Separation in Mixed Polysaccharide Gels
Authors: Matsukawa Shingo , Flores Stephen L. , Geonzon Lester C. , Bacabac Rommel Gaud
Published: February 2020

Phase separation behavior has been studied for the mixed polysaccharides of kappa carrageenan (k-carr) and iota carrageenan (i-carr). Temperature dependence of G’ and G” for the mixture solution measured by dynamic rheological measurement showed two step increases in cooling process, suggesting the individual network formation of k-carr chain and i-carr chain at gelling temperatures (Tg) corresponding to Tg for pure each solution of k-carr and i-carr. The particle tracking method using fluorescent particles with diameter of 100nm was carried out for the mixtures indicating the formation of phase separated structure in the mixture. It was also indicated that the local viscosity of k-carr rich phase was lower than that of pure k-carr solution with the same concentration and the local viscosity of i-carr rich phase was higher than that of pure i-carr solution, suggesting that each phase contions other carrageenan chain. The large amplitude oscillatory shear (LAOS) measurements for the mixtures with various mixing ratios were also measured to investigate the effect of the phase separated structures on the physical property. The response of strain against the large deformation showed characteristic behaviors corresponding to the change of mixing ratio, suggesting a transitional change of phase separation structure with the change of volume ratio of each phase.
3D Printable Energy Storage Crystalline Gels Using Mask-Projection Stereolithography
Authors: Mao Yuchun , Miyazaki Takuya , Sakai Kohei , Gong Jin
Published: February 2020

Phase change materials (PCMs) are considered one of the most reliable latent heat storage and thermoregulation materials. In this paper, a vinyl monomer is used as phase change material to synthesize gel. Using the light-induced polymerization 3D printing technique, we synthesize the energy storage gel and shape it on 3D printers at the same time. iBox Nano and Lumi Forge are used to print our crystalline gels through mask-projection stereolithography. By adjusting layer thickness, exposure time and first layer settings, gels are shaped into several formations successfully. Infrared images, DSC and WAXS test indicate the printed objects have phase transition behaviors and can provide energy storage capacity. Also, the effects of monomer ratios on phase change enthalpy and phase transition temperature are investigated.
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,
Replication of One-Dimensional Composite Nanostructures with Enhanced Mechanically Robust and Thermal Conductivity
Authors: Muanchan Paritat , Kurose Takashi , Ito Hiroshi
Published: February 2020

Nano–engineered surfaces inspired by nature of gecko feet and cicada wings were widely mimicked to replicate the architectural nanostructures on various polymer films. These natural surfaces often provide multifunctional properties and advanced material surfaces such as adhesiveness, hydrophobic surfaces, bio–medical applications, nanosensing materials, catalytic scaffold materials, and energy storages. In this study, vertically aligned composite nanostructures (VACNs) of polystyrene (PS)–graphene nanoplatelets (GNPs) (1.0–5.0 wt/wt%) were precisely replicated by thermal nanoimprint with anodic aluminum oxide (AAO) template. Implications of the reinforced nanofiller on nanostructured surface properties including physical, chemical, thermal, and mechanical properties were investigated. The one-dimensional (1D) composite nanostructures of PS–GNPs with the length of 10–70 µm and diameter of 100 nm were fabricated, resulting the enhancement of surface wetting ability in the water contact angle from 87±3o (flat film) increased to 132±2o. The increase in surface properties including friction coefficient, surface durability (See Figure 1, left), surface modulus and hardness of the PS–GNPs nanostructures as compared with the neat PS nanostructure, were also respectively obtained. The glass transition temperature (Tg
) of PS–GNPs nanostructures was shifted toward about 1.0 to 4.0 oC as compared with their bulk composites because of the immobilization of the polymer chain owing to confinement and surface interfacial interaction effects at the nanoscale within graphene and AAO template. Interestingly, it was found that thermal conductivity of PS–GNPs nanostructures became higher than their composite films due to the 1D property caused by the control of in–plane orientation of GNPs nanofiller within AAO (See Figure 1, right). The maximum thermal conduction of 1D nanostructure of PS–GNPs 5.0 wt/wt% up to 1.28 W/m.K can be obtained in this study. Higher thermal stability of the PS–GNPs nanostructures than that of PS nanostructure was also shown.