bluuebunny/crossref_metadata_2025 huggingface dataset:
Vertically Aligned and Tree-like Carbon Nanostructured for Electrode of Electrochemical Capacitors
Authors: Ghosh Monalisa , Mohan Rao G
Published: February 2020

Vertically aligned and tree-like nanostructures of carbon are grown by using plasma enhanced chemical vapour deposition (PECVD) method using electron cyclotron resonance (ECR) plasma system. These nanostructures consist of a multiwalled carbon nanotube which is aligned perpendicular to the surface of the substrate with carbon films attached to it like “branches” of a tree giving the structure a tree like appearance. The thin film of these nanostructures is deposited in a ECR plasma system on a nickel seed layer with a microwave power of 500 W using acetylene and hydrogen gas in 2:1 ratios as the source gases, at a working pressure of 7x10-4 mbar in presence of a negative substrate bias of 200 V 1. As the material with its vertical alignment and tree-like morphology has a very high exposed surface area, this material was speculated to act as a high-performance electrode of electrochemical capacitors (EC) or supercapacitors. The unique three-dimensional morphology of the material gives a high surface area with less areal footprint of the material.

The electrochemical performance of the material as electrode of EC has been studied by depositing the material of thickness 1 μm on circular stainless-steel substrates of diameter 12 mm (area 1.13 cm2). 1 M Na2SO4 solution in deionised water is used as the electrolyte for the EC with absorbed glass mat as the separator between the two nanostructured electrodes. The entire assembly is done inside Swagelok type cell for testing the electrochemical performance. The EC showed a specific capacity of 920 μF/cm2 (9.2 mF/cc) at a scan rate 0.1 V/s which is higher than the reported values for vertically aligned carbon nanotube.2–4 A rectangular cyclic voltammetry curve is observed even at a voltage of 1 V/s. The results indicate that this material is a promising candidate for electrode material of supercapacitor.

References

M. Ghosh and G. M. Rao, Carbon
133, 239–248 (2018).

B. Hsia, J. Marschewski, S. Wang, J Bin In, C. Carraro, D. Poulikakos, C. P. Grigoropoulos and R. Maboudian Nanotechnology, 25, 055401(9pp) (2014)

T. Chen, H. Peng, M. Durstock, and L. Dai, Sci. Rep., 4, 1–7 (2014).

C. L. Pint et al., Carbon N. Y., 49, 4890–4897 (2011)

Figure 1
A Mechanism for the Enhancement of the Catalytic Activity of Graphene As a Support Material for Oxygen Evolution Reaction Based on Mixed Potential Theory
Authors: Reda Mahmoud R. , Reda Ghazi
Published: February 2020

Catalysts for oxygen reduction and evolution reactions are at the heart of key renewable-energy technologies including fuel cells and water splitting.[1] Currently, there is intense research for new catalysis systems that are highly efficient, low cost, and environmentally friendly in light of the global energy issues.Efficient electrocatalysts for oxygen evolution reaction (OER) represent a critical component in various energy technologies, such as solar cells, metal–air batteries and hydrogen generation from water splitting.[2]

The applicability of a composite of graphene with electroactive material as catalyst for OER is rapidly growing. The growth was due first to the enhancement of the rate of OER which was observed by many researchers when composing the electroactive catalyst with graphene. Second due to the fact that the production cost of graphene in large quantities is much lower than that of carbon nanotubes. Third to the remarkable properties of graphene reported so far include high specific surface area,excellent mechanical strength and fracture strength, unparalleled thermal and electricity conductivity excellent pliability (the quality of being easily bent) , and unprecedented impermeability, plus fascinating electronic properties such as the quantum Hall effect.[3]

Many researchers discovered that the there is an enhancement to the rate of OER when graphene is used as a support for the OER catalyst [4,5]]

Here we show that the mixed potential theory[5] predict that the enhancement of the electrode reaction require two important factors.The first is a large surface area of graphene and the second is the high electric conductivity of graphene which implies that graphene acts as a cathodic electrode conjugating the anodic reaction (OER).

[1] S. Ratha et al. Solid State Electrochem, 20,285 (2016).

[2] Z. Jiang et al. J. Mater. Chem. A, 4, 5877 (2016).

[3]Novoselov, K. S.; Geim et al. Science 2004, 306, 666–669.

[4] D. Chen et al.Chem. Soc. Rev., 39, 3157 (2010).

[5] S. Ghosh et al. Inter J. of hydrogen energy 42, 4111(2017).

[6] G.S. Frankel, Chapter 2, Page 17, Fundamentals of Corrosion Kinetics,

file:///home/chronos/u-eb61a46a79ae3aa8b759186c1deadc9a7f33a7e5/Downloads/9789401775380-c2.pdf
Polyoxometalate Chemistry in Carbon Nanotubes
Authors: Newton Graham N. , Jordan Jack , Lowe Grace , Walsh Darren Anthony , Khlobystov Andrei N.
Published: February 2020

Polyoxometalates (POMs) have received considerable attention in recent years due to their rich redox properties and potential applications in energy storage.1 Due to their discrete nature, the use of POMs as components in energy storage devices relies on their stable combination with conductive supports.2 Carbon nanotubes (CNTs) are stable, hollow cylinders made entirely of carbon. These nanostructured carbons are highly conductive, mechanically strong and can be functionalized.3 By encapsulating molecular materials within CNTs, their properties can be enhanced.

This work describes the first report of the encapsulation of the Keggin [PW12O40]3- and Wells-Dawson [P2W18O62]6- heteropolyanions within carbon nanotubes (CNTs), along with detailed structural, chemical and electronic characterization. Transmission Electron Microscopy (TEM) confirms the presence of encapsulated POMs, as well as providing the necessary energy to perform observable chemical transformations within the CNT. Access to POM redox properties from within the CNT upon encapsulation is described, and the POM electrochemistry is shown to be stabilized across a greater range of conditions and cycles than typically possible. Investigations using Raman spectroscopy probe the electronic coupling between the host and guest, showing electron transfer between the two.

Sadakane, M.; Steckhan, E., Electrochemical Properties of Polyoxometalates as Electrocatalysts. Chem. Rev.
1998,
98 (1), 219-238.

Song, Y.-F.; Tsunashima, R., Recent advances on polyoxometalate-based molecular and composite materials. Chem. Soc. Rev.
2012,
41 (22), 7384-7402.

Miners, S. A.; Rance, G. A.; Khlobystov, A. N., Chemical reactions confined within carbon nanotubes. Chem. Soc. Rev.
2016,
45 (17), 4727-4746.
Carbon Spaghetti from the Reduction of Molten Carbonate Salts
Authors: Hughes Matthew , Allen Jessica A , Donne Scott W
Published: February 2020

The synthesis of new forms of carbon is of great use in the production of many new materials and comforts of modern life. The synthesis of carbon has previously been achieved through many paths, however a path that has been given some major interest in recent years as a medium temperature method of producing carbon products with interesting physical and electrochemical characteristics is the reduction of molten carbonate salts to form value-added carbon products [1]. Of these products, it has recently been noted that carbon nanofibers may form during the reduction of molten Li2CO3 in the presence of trace elements of transitional metals [2]. If carbon nanotubes can be formed through the reduction of molten carbonates it would be of great benefit for many fields, embodying a cheap, low energy cost method of producing these materials. This research investigates the formation of carbon tube structures from molten Li2CO3-K2CO3-Na2CO3 eutectic at 600°C-700°C using copper substrates (Figure 1). Findings suggest that optimal conditions for nanotube synthesis involve nucleation and growth steps, which occur concurrently with the formation of further carbon phases. The formed fibers are hollow tubes which may be capped unless broken, with two major size distributions, thick tubes and thin tubes. The thin tubes have diameters in the order of 300-400 nm.

[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.

[2] Ren, J., et al., One-Pot Synthesis of Carbon Nanofibers from CO2. Nano Letters, 2015. 15(9): p. 6142-6148.

Figure 1
Flexible Micro-Supercapacitors Based on Interdigitated Electrodes of Flash Lamp Annealed Graphene and Carbon Nanotube Composites
Authors: Myung Yusik , Jung SungHoon , Kim TaeYoung
Published: February 2020

We fabricate graphene-carbon nanotube based flexible micro-supercapacitor, using flash lamp annealing. Flash lamp annealing enables the rapid reduction of graphene oxide to graphene in a millisecond time scale and also favors the formation of highly ordered open network of graphene. Interdigitated micro-sized patterns were designed on graphene oxide-carbon nanotube hybrid thin film via laser ablation. Then, flash lamp annealing process converts the insulating graphene oxide to reduced graphene oxide that is conducting at accurate locations. The resulting interdigitated flash lamp annealed graphene-carbon nanotube was then tested as electrode materials for electrochemical capacitors. The electrochemical performance of the electrodes will be presented in terms of volumetric capacitance, energy density and power density.
Novel Process Development of Pyrolytic Carbon Devices
Authors: Gastian Loren , Finnegan Patrick Sean , Washburn Cody M , Dyck Christopher , Burckel D Bruce , Blecke Jill , Rector Michael N , Pfeifer Kent B. , Satches Michael R.
Published: February 2020

Sandia National Laboratories has developed novel approaches to integrate pyrolytic carbon as a viable alternative material in microelectronic devices. Our work demonstrates fabrication of simple single layer and multiple layer devices, targeting future microelectronic applications.

We demonstrate a patterned photoresist on a silicon (Si) substrate, followed by a high temperature bake, and a xenon difluoride Si etch release process as a simple fabrication approach. Loading nanomaterials into the pre-pyrolized polymer establishes the capability to tune specific mechanical and electrical properties. Micromachining blanket carbon films using a dry etch process, allows for precise critical dimension control, and the ability to integrate carbon into complex multilevel device processing. Carbon is durable, adaptable, highly conductive, inexpensive, and easy to produce.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed in the article do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Figure 1) SEM image of cantilever array dry etched and released in xenon difluoride.

Figure 1
Nanoscale Electrochemical Imaging of Aligned Semiconducting and Metallic Single-Walled Carbon Nanotube Bundles
Authors: Kumatani Akichika , Okada Takeru , Yasufumi Takahashi , Shimura Miyu , Shiku Hitoshi , Samukawa Seiji , Matsue Tomokazu
Published: February 2020

Carbon nanotubes have been studied in the variety of research fields from electronic devices to energy harvesting applications [1]. In general, their unique properties come from their ideal one-dimensional structure and tremendous metallic or semiconducting behavior depending upon their chirality. For energy application, it is an important issue to develop a good separation technique for the metallic and semiconducting single-walled carbon nanotubes (SWNTs) in large volume and to understand their electrochemical activities of both types of nanotubes. Recent progress for separation between metallic and semiconducting of has been developed. For example, a gel-based separation technique reported by Tanaka and co-workers [2]. Also, Unwin’s group has revealed the electrochemical activities for each type of the individual SWNT by scanning electrochemical cell microscopy [3].

In this study, we have at first created aligned SWNT bundles by dielectrophoresis [4] using by the commercially available suspension created by a gel separation technique. The aligned nanotube samples were prepared from either semiconducting or metallic nanotube suspension. Then, scanning electrochemical cell microscopy with a single-barrel nanopipette [5] was applied to each sample for the detection of the existence of the other property of the nanotube, referring to the difference in electrochemical activities between semiconducting and metallic nanotubes [3].

[1] M. F. L. De Volder et al., Science 339, 535, (2013). [2] T. Tanaka et al., Nano Lett. 9, 1497 (2009). [3] A. G. Guel et al., Nano Lett., 14, 220 (2014). [4] R. Krupke et al., Science 301, 344 (2003). [5] Y. Takahashi et al. Nat. Comm. 5:6450 (2014).
3D Printable Particle-Type Double Network Gels Studied with Scanning Microscopic Light Scattering
Authors: Tamate Hideaki , Khosla Ajit , Kabir M. Hasnat , Kawakami Masaru , Furukawa Hidemitsu
Published: February 2020

We are conducting research on fine particle preparation double network gel (P-DN gel) which can be applied to 3D printer technology and is capable of high-intensity three-dimensional freeforming. Like the double network gel, the P-DN gels is composed of monomers having two different structures, a hard and brittle mesh structure (1st gel) and a flexible and extensible network structure (2nd gel). In our previous studies, the structure of the P-DN gels has been investigated with a scanning microscopic light scattering device. In this study, we attempted to improve the accuracy of measurement by adding latex particles to the P-DN gels. As a result, the intensity of the scattered light was emphasized compared with ordinary P-DN.
(Invited) Polycarbonate-Based Biodegradable Hydrogels for Biomedical Applications
Authors: Fukushima Kazuki
Published: February 2020

Hydrogels are often used as a powerful tool for topical drug delivery and scaffold in biomedical fields. PEG-based hydrogels are among most studied due to its high biocompatibility, however, they are not technically biodegradable and bioabsorbable. Recent advance in catalysis and monomer synthesis enables now formation of a variety of fictionalized biodegradable polymers in particular using an aliphatic polycarbonate platform, namely PMTC. By using the PMTC platform, a thermoresponsive polycarbonate with tunable amphiphilicity that affords LCST-type reversibility and antimicrobial hydrogels have been developed. In the presentation, both synthetic strategy and evaluation of the hydrogels will be discussed.
(Invited) Thixotropic Gel Electrolyte Consisting of Imogolite and Ionic Liquid
Authors: Shikinaka Kazuhiro , Tominaga Yoichi
Published: February 2020

Electrolytes are fundamental materials that have been used in various industrial fields, for example, in batteries. Liquid electrolytes, though widely used, lack safety and moldability because of the inclusion of organic solvents and the inherent fluidity. The superior safety and moldability of solid electrolytes make them possible alternatives to liquid electrolytes. However, the ionic conductivity of solid electrolytes is lower than that of liquid electrolytes. Recently, a gel-type electrolyte, which combines the high ionic conductivity of liquid electrolytes and the safety of solid electrolytes, has been reported. However, the gel-type electrolyte needs various specific techniques for molding.

In this presentation, we report a quasi-solid electrolyte comprising a transparent thixotropic gel swelled by an ionic liquid (IL) that is formed by a framework of cylindrical inorganic ‘‘imogolite’’ nanotubes. ILs are molten salts consisting of weakly coordinated cations and anions; ILs exhibit melting points below 100 ºC, low vapor pressure, high thermal stability, and high ionic conductivity. Thixotropy as well as stimuliresponsive liquid/solid phase transitions are important for molding of materials in numerous industrial processes (for example, paints and ceramic sols). An application of thixotropic nature to electrolyte will realize its free molding in accordance with the shape of the conduction interface that is difficult for ordinary liquid/solid/gel electrolytes.

Imogolite (IG) is nanotube-like clay mineral, which has a rigid fibrous structure in the form of a single-walled aluminosilicate cylindrical inorganic polymer, with the composition (HO)3Al2O3SiOH. The outer and inner surfaces of IG are covered with Al(OH)2 (proton-capturing) and Si(OH) (proton-releasing) groups, respectively. Recently, we found that mixtures of IG and dicarboxylic acids (DAs) in water resulted in the formation of homogeneous gels, consisting of networked IGs at a mixing ratio, molar ratio of –Al(OH)2 vs. carboxyl groups in DA, of 1 : 1. The gels consisting of IG and DA such as maleic acid (hereafter denoted ‘‘IG–DA gel’’) exhibited hysteresis-free thixotropic behavior. In this study, the thixotropic electrolyte was obtained by substitution of water in the IG-DA gel to ionic liquid.

Because of its transparency, moldability, thermal stability, and high ionic conductivity (Figure), the thixotropic gel electrolyte can be used in various applications such as free-moldable conductive and anti-icing coatings, and battery electrolytes. The transparency of the quasi-solid electrolyte would prevent damage to the base materials. Furthermore, specific abilities of the IG thixotropic gel, such as macroscopic supramolecular chiral ordering of the IG nanotubes and electrorheological responsiveness of the IG, indicate significant potential for the use of these IG–DA–IL based quasi-solid electrolytes as chiral sensing materials, multi-stimuli-responsive actuators, etc.

Figure 1
(Invited) Volume Phase Transition of NIPA Gels and Its Relation to the Inhomogeneity Caused By Extremely Multifunctional Crosslinker
Authors: Nishio Izumi , Saito Azusa , Kamiya Suguru , Okada Shunsuke , Nojima Megumi , Takashima Akito
Published: February 2020

NIPA-Bis gels with low fraction of cross-linkers undergo discontinuous volume change at the specified temperature in water (Volume phase transition). Concerning the critical behavior of gels, NIPA hydro-gels with BIS (NIPA-BIS gels) are the most well studied gels. Y. Li et al.
(1) and K. D. Arai et al. (2) obtained the critical exponents of NIPA-BIS gel.

One of the most extreme gel with multi-functional crosslinker is a hydrogel crosslinked with small crystals of Laponite reported by K. Haraguchi et al.
(3); single Laponite crystal consists of about 2000 unit cells on average, and it has discotic form with diameter of about 30 nm and thickness of about 1.0 nm in aqueous solution. When the Laponite crystals are used as cross-linker, each crystal crosslinks a few thousand of chains due to the silanol groups on the surface of the crystal.

The NIPA-Laponite gels change the volume drastically by the temperature change and these gels are tough against external force. However, discrete volume change (volume phase transition) was not observed even at the very low fraction of crosslinker. This fact indicates that the number of the crosslinkers are very small compared to the BIS crosslinker, and the structure of the gels become very inhomogeneous.

Using the inhomogeneity as the keyword, we will discuss about the hysteresis loop and minor loops observed from NIPA-Lapomite gel.

References

(1) Y.Li and T.Tanaka, J.Chem.Phys.,90, 5161,(1989).

(2) K. D. Arai, A. Saito, K. Ito, Y. Uematsu, T. Ueno, Y. Fujii, and I.Nishio, Phys. Rev. E 87, 022603, (2013).

(3) K. Haraguchi, T. Takehisa, and S. Fan, Macromolecules, 35, 10162 (2002).

Figure 1
Freezing-Induced Mechanoluminescence of Cross-Linked Polymer Gels Based on Mechanocleavable Dynamic Carbon-Carbon Covalent Bonds
Authors: Kato Sota , Ishizuki Kuniaki , Goseki Raita , Aoki Daisuke , Otsuka Hideyuki
Published: February 2020

Polymer mechanochemistry is a fundamental research field to understand how macroscopic mechanical forces are applied to polymeric materials. As a branch of mechanochemistry, mechanochromism, changing color in response to mechanical stress, has been achieved by various stimuli such as tension, compression, shearing, and sonication. Surprisingly freezing also induces mechanical stress. Previous study of our research group showed freezing-induced mechanochromism (FIM) of polymer gels, where diarylbibenzofuranone (DABBF) derivatives at the cross-linking points acting as the color-changing mechanophores was homolytically cleaved to form blue-colored radical in response to shear force induced by freezing.1 In this study, freezing-induced mechanoluminescence was achieved by the introduction of tetraarylsuccinonitrile (TASN)2 skelton as a yellow light-emitting mechanophore into the cross-linking points of polymer gels (TASN gel, Fig. 1). FIM of TASN gel enhanced capability to see mechanical stress with not only pink coloration but also yellow light emission under UV irradiation. The mechanism and characteristics of FIM were studied with the quantitative evaluation by electron paramagnetic resonance (EPR) measurements, revealing that the network structure3 and solvent affinity with polymer chain had good correlations with the dissociation behavior of TASN in FIM.4

Fig. 1 Freezing-induced mechanoluminescence of TASN gel.4

H. Otsuka et al., Angew. Chem. Int. Ed.
2015,54, 6168-6172.

H. Otsuka et al., Chem. Commun.
2017, 53, 11885-11888.

H. Otsuka et al., J. Am. Chem. Soc.
2014,136, 11839-11845.

S. Kato, K. Ishizuki, D. Aoki, R. Goseki, H. Otsuka, submitted.

Figure 1
Anomalous Friction Phenomena on Agar gel Surfaces under Sinusoidal Motion
Authors: Shinomiya Koki , Mayama Hiroyuki , Nonomura Yoshimune
Published: February 2020

The friction phenomena on the gel surface under accelerated conditions are important to design biofunctional materials. However, there are few reports on friction under such nonlinear conditions. In the present study, the effects of velocity, vertical force, and gel hardness on the friction force were evaluated between two flat agar gels under sinusoidal motion. We found ultra-low friction conditions that the friction coefficient is almost zero on the gel surface. In addition, the profile of the friction force was different between the outward and homeward processes in the reciprocating sliding motion. For example, at a vertical force W = 0.98 N and angle rate ω = 2.1 rad s-1, the friction coefficient was 0.30 at friction velocity V =10 mm s-1 and then reduced to 0.02. Such characteristic friction profile is caused by long relaxation time on the gel surfaces. When the gel substrate is rubbed with shorter friction time than the relaxation time τ from static friction to kinetic friction, the morphology of the gel surface becomes unstable. Under such conditions, the formation and extinction of thick liquid film can induce super lubrication state and the asymmetric friction phenomena. These findings are useful not only for developing biofunctional materials but also for understanding non-equilibrium phenomena in soft biological systems.
Physical Properties of Hydrogel Objects By 3D-Printing
Authors: Saito Azusa , Ota Takafumi , Yoshida Kazunari , Tase Taishi , Sato Kei , Tanaka Masanobu , Takamatsu Kyuichiro , Khosla Ajit , Kawakami Masaru , Furukawa Hidemitsu
Published: February 2020

Since the gel has soft physical properties, it was difficult to process by conventional cutting or casting, but 3D gel printer was developed, and three-dimensional free modeling of the gel became possible. In this study, it is presented that the relationship between printing parameters of a 3D gel printer "Soft and Wet Intelligent Matter-Easy Realizer (SWIM-ER)" and mechanical properties of the fabricated gel objects by SWIM-ER. The printer can fabricate hydrogel objects by scanning of ultra-violet (UV) light irradiation (photopolymerization). Various hydrogels objects were printed with different scanning velocity of UV light. We measured the water content and mesh sizes of gel objects utilizing Scanning Microscopic Light Scattering (SMILS). Furthermore, we also printed the gel objects with multiple scan rates with constant UV light irradiation energy, and measured sizes of gel objects, and performed the compression test. It was observed that the physical properties of printed hydrogel objects are strongly related with 3D printing parameters due to difference in crosslinking density of polymer network.[1]

Ref.

[1] Takafumi Ota, et al., Mechanical Engineering Journal, 5, 1, 17-00538 (2018).
3D Gel Printing for Jellyfish-Mimic Robot
Authors: Takishima Yuki , Saito Azusa , Yoshida Kazunari , Takamatsu Kyuichiro , Khosla Ajit , Kawakami Masaru , Furukawa Hidemitsu
Published: February 2020

Various kinds of underwater exploration techniques have been developed. For instance, submersible research vehicles and autonomous underwater vehicle (AUV) have been used for observation of underwater conditions, in addition to the technique of fixed-point observation. However, such research vehicles and conventional AUV are difficult to control, are expensive, and are usually made with non-biodegradable materials such as metals. In contrast, jellyfish is the most efficient swimmers, traveling for long distance with saving energy by drifting in the ocean, its body can be decomposed after death, and safe for surrounding creatures. Therefore, we are developing the jellyfish-mimic AUV using a hydrogel. For designing a Jellyfish-mimic AUV robot, it is preferable to introduce a soft actuator driven by water pressure, as it requires low electric power and it is eco-friendly. In this study, we prototyped a Jellyfish-AUV robot using a soft material and a soft actuator. While it is ideal to make a robot body with hydrogel it is difficult to make the actuator with hydrogel. Here, we report a silicone-based hydraulically-driven soft actuator that can make a bending motion of umbrella-shaped bell of artificial Jellyfish. We utilized the Pneunets Bending Actuator for designing the actuator, and the detailed information of this actuator is shown in the website of Soft Robotics Toolkit (see https://softroboticstoolkit.com/book/pneunets-bending-actuator). The actuator is composed of inflation parts, basis, and copy paper placed between them. We poured into the 3D printed mold made with polylactic acid (PLA) and preserved at room temperature for 4 h to cure the silicone parts (inflation parts and basis). Copy paper was sandwiched between inflation parts and basis. The size of copy paper was 30 mm × 5 mm. Then, we poured additional silicone resin to combine the parts. By inserting a toothpick into the mold, we made the insertion port of the silicon tube. Before curing, we removed the air bubbles for 20 minutes with a vacuum de-foaming device. Finally, we inserted a silicon tube into the fuselage and attached a syringe for air supply. The behavior of the actuator in salt water was evaluated by image analysis, and the shrinkage factors of gel robots were compared with that of real jellyfish. The results were obtained as shown in Figs.1, 2 and 3. The shrinkage ratio of the jellyfish robot was 46.4 % at the maximum in the case of air injection of 2.8 cm³. The ratio did not reach 56.3 % at the maximum shrinkage ratio of the real jellyfish. To achieve the 56.3 % shrinkage ratio, we have to improve the maximum volume of injection air. Consequently, we have concluded there is a possibility that this actuator can reproduce jellyfish movement.
(Invited) Sweet and Sticky: Mucus Inspired Biomedical Hydrogels
Authors: Kramer Jessica , Schlirf Austin
Published: February 2020

The human body has 200x greater mucosal epithelial surface area than skin, and produces roughly 10L of mucus daily. Mucus gel coatings on epithelial tissues function as hydrating, lubricating barriers and mediate absorption of nutrients, drugs, and pathogens and houses the majority of the microbiome. Despite essential biological roles, mucus remains poorly defined in terms of both composition and physical properties. Mucus is challenging to study because the major protein component is massive (0.5–20 MDa) and heterogeneous mucin glycoproteins. Currently, there are no methods to reproducibly access chemically defined mucins. This roadblock has rendered functional studies of one of nature’s most abundant and essential biomaterials incredibly challenging.

Mucus gels are thought to form via combination of physical entanglement and chemical bonds between individual mucin glycoproteins. We have prepared synthetic mucin glycopolypeptides via polymerization of glycosylated N-carboxyanhydrides (NCAs). We are exploring properties that drive assembly of individual mucin polymers into synthetic mucus gels. We are tuning gel properties (viscoelasticity, pore size, binding ability) by tuning the amino acid functional groups, cross-linker property/density, and glycosylation patterns. Access to tunable synthetic mucus will shed light on the properties of this essential biomaterial and open the door to study diverse epithelial processes such as mucosal transport of nutrients and drugs, as well as infection and immunity.
(Invited) Topology and Toughening of Model Crosslinked Polymers
Authors: Yamaguchi Tetsuo , Onoue Yudai , sawae Yoshinori
Published: February 2020

Toughening of crosslinked polymers like rubbers or gels is one of the most important problems in polymer science. While novel types of tough gels have been developed in the last decade, the toughening principle is not established: most researchers pay much attention to chain length heterogeneity, but little attention to other aspects. In this study, we focus on network topology, which is believed to be essential in complex network. We created macroscopic polymer models made of rubber strings and connecters, and performed fracture experiments of such model polymers with different topological structures. We found that periodic but systematic modifications in local coordination number with keeping the constant mean number (4, in 2D) exhibited great improvement in toughness compared with regular square lattices, and the star polymer network showed the best performance. In our talk, we will explain the details of our experiments and discuss the results by comparing with numerical simulations and theory.
(Invited) Stem Cells and Microenvironments – Applications to Cancer and Regenerative Medicine
Authors: Gerecht Sharon
Published: February 2020

The formation of new blood vessels is crucial for successful tissue regeneration as well as for the growth and spreading of cancer. Human pluripotent stem cells offer a unique opportunity to derive vascular cells from a common cell source. Hydrogels provide a highly controlled three-dimensional (3D) environment that is structurally and biomechanically similar to native extracellular matrix and can provide a rich biochemical landscape as well as biophysical cues to influence cell behavior. In this talk I will present our recent efforts to develop hydrogel matrices to understand how physicochemical cues and downstream signaling pathways impact vascular fate and assembly. Examples will include interface along stem cell differentiation, during wound healing and vascular regeneration, and angiogenesis.
Gelation Behaviors of Amylosic Host-guest Supramolecular Networks Depending on Guest Polymers
Authors: Orio Saya , Yamamoto Kazuya , Kadokawa Jun-ichi
Published: February 2020

Amylose, which is a helical polysaccharide, is known to form inclusion complexes with relatively low molecular weight guest compounds by hydrophobic interaction. However, little has been reported regarding the formation of inclusion complexes between amylose and polymeric compounds. The main difficulty in incorporating polymeric compounds into the amylose cavity is that the driving force for the binding is only caused by hydrophobic interactions. Amylose, therefore, does not have sufficient ability to include the long polymeric chains. The author has developed a new method of the polymerization system called “vine-twining polymerization” for the formation of well-defined polysaccharide supramolecules, that is, amylose–polymer inclusion complexes. The method was achieved by phosphorylase-catalyzed enzymatic polymerization of α-D-glucose 1-phosphate (G-1-P) monomer from malooligosaccharide primer to produce amylose, in the presence of hydrophobic synthetic guest polymers. The image of this polymerization system is the similar as the way that the vines of a plant grow twining around a rod.

In this study, we attempted to prepare supramolecular hydrogels composed of amylosic host-guest networks from different guest polymers by the vine-twining polymerization using maltooligosaccharide primer-grafted poly(g-glutamic acid) in the presence of the following guest polymers, polytetrahydrofuran (PTHF), poly(ε-caprolactone) (PCL), and poly(L-lactide) (PLLA). Consequently, we found that the reaction mixture using PTHF totally turned into hydrogel form, whereas the products using PCL and PLLA were aggregated in the reaction mixtures. It was speculated that the different behaviors were owing to stabilities of inclusion complexes as cross-linking points in the networks, depending on the guest polymers.
(Invited) Flexible Electronics in ITRI
Authors: Hu Je Ping
Published: February 2020

Taiwan has strategically invested in flexible electronics for over 10 years. With Taiwan government’s support, ITRI has established the first flexible electronics pilot laboratory in Asia in 2007. The purpose is to facilitate the development of flexible electronics worldwide. During these years, many Taiwanese companies have entered the stage of mass production in flexible electronics, including E-paper, printed touch panels, printed RF-ID antenna, smart cards with displays, flexible pressure sensors, solar cells, etc. They have played key roles in the world.

In the recent years, there are three focuses in the flexible electronics pilot laboratory: 1) roll-to-roll for production revolution; 2) OLED lighting for sun-like color; 3) Bio-sensor platform. With over twenty leading companies, ITRI has developed cutting-edge flexible electronic technologies, such as roll-to-roll touch panels using 3um fine line printing based on 100um ultra-thin glass, free-shape ultra-thin substrate cutting technique with >500MPa bending strength, OLED light engines in pilot production scale, digital manufacture for industry. In this April, ITRI debuted the first high-end OLED lighting modules using full roll-to-roll process.
Flexibility and High-Rate Discharge Properties of Organic Radical Batteries with Gel-State Electrodes
Authors: Iwasa Shigeyuki
Published: February 2020

Technology related to Internet of Things (IoT) and wearable devices has just begun to be actively developed. In that field, the demand for thinness and flexibility has increased in secondary batteries due to the structural compatibility of IoT or wearable devices such as vital sensors.

We have been developing organic radical batteries (ORBs) with cathodes consisting of nitroxyl radical polymers such as poly(2,2,6,6-tetramethylpiperidinyl-N-oxyl-4-yl methacrylate) (PTMA). Our previous work showed that ORBs with PTMA cathodes have high rate capabilities. PTMA is also known to be changed into a gel-like state due to the absorption of organic electrolytes. The PTMA gel in the electrodes is certain to be suitable for thin and flexible batteries because it is hardly damaged when it is repeatedly bent and unbent. However, the state of the PTMA cathodes in the battery has not been characterized, and the flexibility of ORBs with the PTMA cathodes has not been investigated so far.

The objective of this work is to clarify the state of the cross-linked PTMA cathodes in the battery and flexibility of the ORBs. We also report the electrode preparation method of cross-linked PTMA cathodes to obtain practical ORBs with both high rate discharge properties and excellent cyclability.

Cross-linked poly(2,2,6,6-tetramethylpiperidinyl-N-oxyl-4-yl methacrylate) (PTMA) gel used in organic radical batteries (ORBs) is characterized by rheological measurements, and the micro structure of gel-state cathodes is observed using low vacuum SEM. The storage elastic modulus of the cross-linked PTMA gel is under 10 kPa which is in the range of soft gel. It suggests that the PTMA cathodes are fairy flexible in the battery. The ORBs with the cathodes made from cross-linked PTMA/vapor grown carbon fiber (VGCF) composite show excellent discharge rate properties (20C/1C capacity 91%). The structure of needle-like VGCF penetrating PTMA particles in the composite results in excellent rate capabilities. In the PTMA gel cathode, the cross-link structure of the PTMA has the effect of maintaining homogeneous dispersion of VGCF, which gives improvement in cyclability. The capacity and resistance of the ORBs are maintained in the initial state after repetitive bending 250 times. We demonstrate that the gel state cross-linked PTMA is a promising electrode material for practical flexible batteries.
Performance Evaluation of Screen-Printed Paper-Based Glucose Biofuel Cell Using MgO-Templated Porous Carbon Material for Self-Powered Diaper Sensor
Authors: Fujimura Yuki , Hoshi Yoshinao , Shitanda Isao , Tsujimura Seiya , Itagaki Masayuki
Published: February 2020

Recently, biofuel cells have been attracted attention as compact and safe wearable power sources [1]. We have reported paper-based glucose biofuel cells in which porous carbon materials were printed by screen printing technique [2,3]. The biofuel cell can be expected to be applied to self-powered urine sugar biosensor for inspecting diabetes. In this study, we fabricated a disk-shaped paper-based biofuel cell array for power source of a self-powered diaper sensor. In this paper, we discuss a performance of a single biofuel cell.

The paper-based biofuel cell anode and cathode were fabricated by screen-printing. The MgO-templated porous carbon ink was printed for bioanode and biocathode. Tetrathiafulvalene (TTF) and glucose oxidase (GOD) was modified on the bioanode surface. The biocathode was prepared by modifying bilirubin oxidase (BOD). The biofuel cell was prepared by stacking the non-printed side of paper substrate of bioanode and biocathode by using water repellent double-sided tape. During the measurements, the edges of the paper substrate of bioanode, the biocathode and the cell were immersed in the 1 M phosphate buffer solution containing glucose.

Figure1 shows cyclic voltammograms of the bioanode in a phosphate buffer containing 100 mM glucose at 37 ℃. Compared to the background current measured in 0 mM glucose solution, a catalytic current wave related to glucose oxidation was clearly observed in the presence of glucose, and the maximum current density was 7.4 mA cm-2 at 0.5 V. Figure 2 shows the relation between power density and operating cell voltage with different concentration of glucose at 37 ℃. It was confirmed that the output power density increased along with increase of the glucose concentration. Finally, a disk-type biofuel cell array was prepared and output evaluation was carried out.

Acknowledgement

This work was supported by JST-ASTEP Grant Number AS272S004a.

References

(1) L. Zhang et al., Biosens. Bioelectron. 35 (2012)155-159.

(2) I. Shitanda et al., Chem. Commun. 49 (2013) 11110-11112.

(3) I. Shitanda et al., J. Power Sources, 360 (2017) 516-519.

Figure 1
(Invited) Wearable Printed Pressure Sensors with Ferroelectric Polymer for Healthcare Applications
Authors: Sekine Tomohito , Takeda Yasunori , Matsui Hiroyuki , Kumaki Daisuke , Dos Santos Fabrice Domingues , Atsushi Miyabo , Tokito Shizuo
Published: February 2020

Flexible printed organic electronics have various advantages over conventional inorganic electronics. These organic devices such as sensors and actuators can be fabricated on a plastic thin-film substrate with low-temperature printing processes[1,2]. Especially, physical sensors based on a ferroelectric polymer have a great potential in the development of wearable and disposable health-care devices such as pressure sensors. As the ferroelectric polymer for the sensors, poly(vinylidene difluoride trifluoroethylene) [P(VDF–TrFE)] (Piezotech, 62-010, VDF:TrFE molar ratio of 75:25) is the most promising material because of high ferroelectricity and piezoelectricity[3]). Moreover, the P(VDF–TrFE) is compatible with printing processes because of its solubility in several organic solvents[4,5].

A representative printed physical sensor based on P(VDF–TrFE) was fabricated on a flexible plastic film substrate by screen printing method. PEDOT:PSS (Heraeus, Clevios SV 4 Stab) was used for the top and bottom electrodes. Thicknesses of the P(VDF–TrFE) layer and the electrodes were 2 µm and 1 µm, respectively. The P(VDF–TrFE) layer could generate the voltage of 50 mV by applied pressure of 50 kPa[5]. The generated voltage clearly depended on the thickness of P(VDF–TrFE) layer. Our printed sensor exhibited high sensitivity in the low pressure region, which is indicating the potential application to wearable sensors which monitoring health condition of human. In order to monitor the health condition of a volunteer, the sensor was attached to the skin near the neck using a skin-compatible adhesive patch. We have succeeded in the detection of the pulse rate with 55 pulse per minute. These results indicate that our P(VDF–TrFE) based sensor is significantly promising for wearable health-care applications.

The detection of the pulse rate from volunteer was authorized by the Ethics Committee of Yamagata University (authorization code: 29-2).

This study was partially supported by the Japan Science and Technology Agency (JST). T. S. would like to thank all member of Research Center for Organic Electronics in Yamagata University, Piezotech and Arkema corporation.

[1] K. Fukuda et al., Sci. Rep., 3, 2048 (2013).

[2] S. Conti et al., Adv. Mater. Technol., 2, 1600212 (2017).

[3] D. Thuau et al., J. Mater. Chem. C, 5, 9963 (2017).

[4] G. Knotts et al., Appl. Phys, Lett., 104, 233301 (2014).

[5] T. Sekine et al., Sci. Rep., 8, 4442 (2018).
(Invited) Carbon Nanotubes for High-Performance Flexible Electronics and Integrated Smart Sensor System
Authors: Hu Youfan
Published: February 2020

As the information processing part in flexible integrated systems, there are several basic requirements for the integrated circuits (ICs) in addition to flexibility, including high speed, low power consumption, medium to large scale integration, etc. Currently there is no solution that can meets all the requirements. Here we present our recent progress in high performance flexible thin film transistors based on carbon nanotubes (CNTs). The transistors exbit large on-state current, high mobility (>80 cm2V-1s-1), small subthreshold slop (<70 mVdec-1), and large current on/off ratio, all with an operating voltages of 2 V. The developed fabrication approach presents high yield and the transistors’ performances are highly uniform with well controlled threshold voltage distribution, which enable the realization of various logic gates on flexible substrate. Finally, an integrated smart sensor system with in-situ signal processing capability for human body monitoring based on CNTs was demonstrated.
Fabrication of Flexible Metal Oxide Thin Film Transistor By Indigenously Developed Spray Pyrolysis Unit
Authors: Omprakash S S , Naveen Kumar S K
Published: February 2020

The deposition of polyvinyl alcohol (PVA) dielectrics and semiconductor Zinc oxide (ZnO) thin film is developed by custom designed spray pyrolysis unit. The solutions for spray are prepared by PVA and zinc acetate dehydrated as precursor materials. These solutions are deposited on a substrate such as Aluminium coated polyimide and polyimide film The Aluminium is used as Source and drain electrodes. PVA and ZnO deposited on these electrodes is act as the gate oxide and channel layers for thin film transistor (TFT). Gate electrodes are deposited by thermal evaporation of Al using shadow mask method. Finally, top gated TFT is fabricated.

Results: The morphology of the films was characterized by FESEM which confirmed that the film was uniform with no cracks. The XRD results are confirm the amorphous nature of ZnO thin film. The PVA coatings are also examined for electrical properties like C-V. The thickness and roughness of films were measured using optical Profilometer. The optical studies of the film are studied and the band gap is calculated using Tauc plot. A study has been performed on ZnO for its electrical characteristics such as mobility and resistivity. The TFT characteristics like input and output has been carried out.

Keywords: TTF, Spray pyrolysis, PVA, ZnO,

Figure 1
Quantum Chemistry As a Tool for Materials Development
Authors: Correa Andrea
Published: February 2020

In the past, new materials have been developed by empirically correlating their chemical composition, and the manufacturing processes used to form them, with their properties.

The rapid advancements in quantum theory, computer science, and computational power brought about tremendous developments in materials research. Nowadays quantum chemistry, or more generally computational chemistry, can be used as a tool for developments of new materials through a synergic, computational and experimental, work.

In this presentation we will give an overview of how a combination of efficient quantum mechanic calculations and experimental data can lead to new materials development through catalyst rational design. In the first part, we will focus our attention on polymeric materials by Ziegler-Natta catalysis, and production of new materials through organometallic metathesis. Then, application quantum chemistry to the study of solar cell systems will be discussed.