bluuebunny/crossref_metadata_2025 huggingface dataset:
Plasmonic Cu Nanoparticles Prepared By DC Magnetron Sputtering
Authors: Gustavsen Kim R , Wang Kaiying
Published: February 2020

Noble metal nanostructures are known for their unique optical property as localized surface plasmon resonance (LSPR), which electromagnetic radiation interacts with the free electrons of the metallic nanostructure, resulting in collective oscillations and thus to a significant strengthening of the local electric field surrounding the particles [1]. Although noble metal such as Ag and Au have been widely known for their plasmonic properties, Cu has often been overlooked due to surface oxidation problems, which significantly reduces the excitation intensity [2]. We present in this paper a systematic study of Cu nanoparticles assembled by direct current (DC) magnetron sputtering on quartz substrates. The effect of deposition time on the optical properties, particle size, and particle spacing has been investigated.

The Cu nanoparticles were deposited in Argon atmosphere with a pressure of 19 mTorr, DC power of 200W, and a substrate temperature of 400°C. Additionally, the Cu nanoparticles were annealed at 400°C in vacuum for 6 hours following deposition. A photograph of the Cu nanoparticles on quartz is seen in Figure 1. From left to right, the color of the samples changes from dark blue with a green hue to a light blue color as the deposition time decreases. Absorbance spectra (250-850 nm) in Figure 2 show that increased deposition time lead to higher absorbance and a slight red shift of the LSPR peak. SEM images indicated that particle size for the individual samples was not uniform, which is seen in Figure 3 (particle size ~8 – 28 nm).

In conclusion, we have demonstrated the fabrication of Cu nanoparticles by DC magnetron sputtering. The particle sizes ranged from ~8 – 28 nm when depositing for 45 seconds. Particle size, geometry, height, and spacing, which are directly responsible for the optical response, are to be investigated on quartz substrates using scanning electron microscope (SEM) and atomic force microscope (AFM).

References

Christy L. Haynes and Richard P. Van Duyne* The Journal of Physical Chemistry B
2001
105 (24), 5599-5611 DOI: 10.1021/jp010657m

George H. Chan,Jing Zhao,Erin M. Hicks,George C. Schatz,* and, and Richard P. Van Duyne* Nano Letters
2007
7 (7), 1947-1952 DOI: 10.1021/nl070648a

Figure 1
Electrochemical Anodization of Dental and Orthopedic Nanotubes
Authors: Shokuhfar Tolou
Published: February 2020

Future prospects for nanotechnology and biomaterials in medical applications appear to be excellent. In orthopedic applications, there is a significant need and demand for the development of a bone implant that is bioactive and exhibits mechanical and surface properties comparable with those of natural, healthy bone. This need arises from the fact that in 2009, $17.2 billion was spent on approximately 1.1 million joint replacement surgeries. The number of such procedures is forecast to be 3.8 million per year by 2030 with corresponding rise in cost burden. This sharp increase stems from an aging population as well as the more frequent use of orthopedic implants in the treatment of severe degenerative and arthritic conditions. Implant failure, either directly or indirectly, is most often caused by loosening (osteolysis) at the bone-prosthesis interface. Implant loosening is the major complication in total joint replacement. Currently, the only option available for countering loosened implant is revision surgery that presents additional clinical challenges due to complexity of the procedure as well as compromised osteogenic local environment due to osteolysis related events. A more attractive and effective approach is to enhance bone regeneration around the implant at the earlier stages to yield higher fixation strength and longevity. Therefor, there is a significant need and demand for the development of a bone implant that is bioactive and exhibits mechanical and surface properties comparable with those of natural, healthy bone. We have successfully modified the surface of orthopedic and dental implants using electrochemical anodization to produce TiO2 nanotubes that exhibit the ability to mimic the dimensions of constituent components of natural bone. We have shown implants modified by TiO2 nanotubes promote osteointegration and can be a successful alternative to conventional implants. In addition, medical implants such as orthopedic, dental, pacemakers, and vascular stents may require subsequent drug therapy regimens to prevent infection, or decrease inflammation. Drug release derived directly from the implant surface rather than systematically can reduce unnecessary side effects and increase efficiency. We have used reverse electrochemical anodization to embed TiO2 nanotube textured implants with minimal amounts of 10nm silver nanoparticles and then tested them against E-Coli, and P-gingivalis bacteria. Our results show that not only can promise to enhance osseointegration but also can fight infection and eliminate chronic inflammation and provide a clinical benefit for a broad range of implant-needing patients.
The Impacts of Zirconia As a Spacer Layer on Fill Factor of Hole-Free Perovskite Solar Cells
Authors: Abdel-Fattah Tarek M , Ebrahim Shaker , Gasmalla Khalid , Soliman Moataz
Published: February 2020

Organometallic trihalide perovskite solar cells have attracted the researchers due to their easy fabrication, low cost and high power conversion efficiencies. Hole-conductor free perovskite solar cell is the most interesting structure to be commercialized due to its manufacturing simplicity, lower cost materials and higher stability compared to the other structures such as p-i-n and n-i-p structures [1-2]. The main issues of this type of solar cells are the poor fill factor and low power conversion efficiency due to the direct contact between TiO2 and carbon, absence of hole transport layer and poor interfacing between TiO2/perovskite interface. To overcome this problem, the influence ZrO2 and spiro-OMeTAD and correlate them with the photovoltaic performance will be presented. Three different cells have been prepared and compared to each other, typically named “cell 1” without ZrO2 spacer layer, “cell 2” with ZrO2 spacer layer between mesoprous TiO2/carbon electrode interface and “cell3” with perovskite doped spiro-OMeTAD with 50 wt%. Different photovoltaic performances were observed and enhancement of the fill factor has been achieved. The strength of our perovskite CH3NH3PbI3 layer has been enhanced with a ratio of 10 wt% of PbCl2, the HTM-free PSCs based on the incorporation ZrO2 “cell 2” has a significant increase in the fill factor more than 0.49, and “cell 1” achieved a higher efficiency of 5.4 %.

References

Chenxi Zhang . Yudan Luo . Xiaohong Chen . Yiwei Chen . Zhuo Sun . Sumei Huang. Effective Improvement of the Photovoltaic Performance of Carbon-Based Perovskite Solar Cells by Additional Solvents, 2016, Nano-Micro Lett. 8(4):347–357.

Using a low-temperature carbon electrode for preparing hole-conductor-free perovskite heterojunction solar cells under high relative humidity. 2016, Nanoscale, 8, 7017

Figure 1: Schematic representation of the cell structure.

Figure 1
Electronic Structures of a Cerasome Surface Model
Authors: Oda Masato
Published: February 2020

Drug therapy is always accompanied by undesirable side effects, because the drug spread out and affect to healthy tissues and organs as well. One of the ways to reduce the side effects is to develop a system that deliver a desired amount of the drug to a diseased part directly. The system is known as drug delivery system (DDS). The construction of the DDS requires the technology to encapsulate the drug and release it around the diseased part. Lipid bilayer vesicles, so-called liposomes, are typical DDS materials. However, liposomes are not very stable because all the lipids are connected via van der Waals interactions. As a result of this low stability, sometimes liposomes cannot reach the diseased part intact. There is a pressing need to develop more stable liposomes capable of encapsulating the drug. Recently, erasomes, i.e., liposomes featuring surfaces reinforced with a siloxane bond network, have been developed. It has been shown that a cerasome can encapsulate the drug and is much more stable than liposomes. Thus, cerasomes are promising materials for DDS. However, the improvement in stability is accompanied by a difficulty in opening the capsule. Breaking the chemical bonds of a cerasome surface requires information about its microstructure and electronic states, although the microscopic properties of cerasomes remain unclear.

In the previous work, we construct a simple cerasome model (figure) to investigate the electronic structures of its surface. Comparing the electronic structures of the membrane model with that of the molecule, we reveal that there are mid-gap states in the membrane model that are not in the molecule. These mid-gap states consist of antibonding states of Si-C bonds that connect the siloxane network and organic parts of the lipid. The existence of the antibonding states in the gap indicates that there is a possibility to break cerasomes with some electronic excitations to the system. However, the previous model is extremely simple, we assume perfect siloxane network, although there are many O- and OH groups on the surface of actual cerasomes. The purpose of this study is to investigate effects of surface substituent groups on the electronic structures of the cerasome model.

We introduce some O- and OH groups in the surface of the model and calculate the electronic strucutres. All calculations are carried out using first-principles scheme based on density functional theory. It is revealed that the energy of the mid-gap states is modulated around 0.2 eV, but still in the HOMO-LUMO gap of the lipids. This result indicates that we can expect that the mid-gap states valid for the realistic cerasomes.

Figure 1
Chitin Nanofiber Transparent Paper: A Structural/Fuctional Material Platform for Green Electronics and Energy Devices
Authors: Jin Jungho
Published: February 2020

Chitin – ‘the cellulose of the sea’ – is a structural polysaccharide that is a major constituent of the exo-/endo-skeleton of marine crustaceans and cephalopods, and is the 2nd most abundant biopolymer on earth only after cellulose. Ever since its discovery in the early 19th century, chitin has been considered a promising material due to its atypical yet compelling combination of mechanical and physicochemical properties, such as high elastic modulus (150 GPa), biodegradability, and excellent biocompatibility. Despite the promising traits, however, it is only quite recent that scientific interest on chitin has thrived and the utilization of chitin for engineering applications has revisited considerably. In this presentation, I will introduce some of my research endeavors to create structural/functional materials (e.g., transparent nanopaper) using chitin nanofibers (ChNF) as the basic building-blocks. I will also describe proof-of-concept examples of electronics and energy devices constructed using the ChNF paper platform.
(Invited) Evaluation of Tailored Organic Molecules for Cathode Passivation in High Voltage Lithium-Ion Batteries
Authors: Odom Susan A. , Kaur Aman Preet , Attanayake N. Harsha , Johnson Christopher
Published: February 2020

Redox-active organic compounds have been explored as electrolyte additives for lithium-ion batteries, for purposes ranging from mitigation of excess current in overcharging cells to passivation of electrode surfaces to stabilize surfaces that would otherwise lead to electrolyte decomposition. Especially when expanding the voltage range in charging of lithium-ion cells, passivation becomes more critical to cell longevity during operation. Electrolyte additives containing purposefully weak covalent bonds have been employed in high-voltage (e.g. NMC cathodes) lithium-ion cells, which are tailored to react with hydrofluoric acid – a product of decomposition of fluorine-containing anions present in the electrolyte. Here we report results from the investigation of organic molecules as electrolyte additives with functionality aimed to react with/at cathode surfaces to form passivating films. These organic molecules with varying oxidation potentials (3.4 V vs. Li+/0 and above) house main group ad-atoms unique from those contained in the electrode, binder, conductive fillers, and electrolyte solutions. This allows for surface imaging and electrolyte analysis to determine the location and reaction of such additives following formation cycling.
Electrolyte Studies Centered Around a Substituted Lithium Cobalt Phosphate Cathode Material
Authors: Delp Samuel A , Allen Jan L , Jow T Richard
Published: February 2020

Current state of the art lithium ion batteries have reached a plateau in energy density. Next generation materials are becoming available and researched. There are two directions being pursued to achieve higher energy density. The first path is to use materials that have higher energy density than the ones currently used, for example, incorporating silicon into the anode or transitioning to lithium as the anode. A second direction is to use cathode materials that are electrochemically active at higher voltages. Lithium cobalt phosphate (LCP) is one example of a cathode material that operates at a higher voltage than state of the art materials (4.8 V vs Li). Pure LCP suffers from severe capacity fade due to structural degradation during cycling. Recently we have been able to increase the cycle life of LCP by the introduction of elemental substitution of iron, chromium and silicon. The major challenge now is that conventional electrolytes are not stable at the elevated voltages at which LCP cycles. The electrolytes must not only be stable at high voltages but also at low voltage if graphite is used as the anode material. Generally, when the oxidative stability voltage of the electrolyte increases, the reductive stability voltage increases causing problems on the anode. The progress of electrolyte development for LCP batteries will be discussed.
Ion Dynamics in Al-Doped Cubic Li7La3Zr2O12 Garnet-Type Single Crystals
Authors: Posch Patrick , Lunghammer Sarah , Berendts Stefan , Uecker Reinhard , Rettenwander Daniel , Wilkening Martin
Published: February 2020

Li7La3Zr2O12 (LLZO) garnet-type materials are regarded as promising candidates for solid electrolytes and have been extensively investigated in the past few years.[1,2] Several studies report on an increase in conductivity by doping with ions to stabilize the cubic structure.[3,4] In the present study we focus on the ionic transport processes in Al-doped LLZO single crystals. To investigate ionic motions we used 7Li nuclear magnetic resonance (NMR) spectroscopy and impedance spectroscopy. With the help of rotating-frame spin-lock NMR spin-lattice relaxation (SLR) we looked at localized and medium-ranged ionic motions, respectively. Impedance spectroscopy was used to shed light on the long range ion dynamics. At room temperature the total conductivity turned out to be 0.082 mS cm-
1 at, which is remarkably good for LLZO with an Al-content of only 0.34 wt%.[5]

Most importantly, 7Li NMR spin-lock NMR of revealed two overlapping diffusion-induced processes that share almost the same activation energy. A similar behavior has recently been seen for Mo-bearing LLZO.[6] Overall, activation energies gathered from spin-lock NMR and impedance measurements are in good agreement with each other; both techniques yield values around 0.36 eV. The solid-state coefficient (D) and the self-diffusion coefficient (Dsd), calculated from impedance spectroscopy and NMR spin-lock SLR, respectively, almost coincide. This excellent agreement points out that the two methods are sensitive to very similar motional correlations functions probing magnetic spin fluctuations and electrical relaxation processes, respectively.

References

[1] S. Ohta et al., J. Power Sources, 2012, 202, 332–335.

[2] B. Stanje et al., Ann. Phys. (Berlin), 2017, 529, 1700140.

[3] D. Rettenwander et al., Chem.
Mater., 2014, 26, 2617–2623.

[4] J. L. Allen et al., J. Power Sources, 2012, 206, 315–319.

[5] H. Buschmann et al., Phys.
Chem. Chem. Phys., 2011, 13, 19378–19392.

[6] P. Bottke et al., Chem. Mater., 2015, 27, pp 6571–6582
Fluorinated Phosphorus-Based Compounds As Multifunctional Additives/Co-Solvents for Advanced Lithium-Ion Battery Electrolytes
Authors: von Aspern Natascha , Diddens Diddo , Stubbmann-Kazakova Olesya , Kozel Volodymyr , Roeschenthaler Gerd-Volker , Winter Martin , Cekic-Laskovic Isidora
Published: February 2020

In today’s society, the utilization of portable energy sources like lithium-ion batteries (LIBs) is of essential worth. However, LIBs still have certain limitations and bottlenecks addressed to nonaqueous aprotic electrolytes, as inevitable components for the operation of the battery.1 With this in line, state-of-the-art nonaqueous aprotic electrolytes (SOTA) reveal different challenges such as electrolyte decomposition and high flammability. One effective and cost favorable approach refers to the introduction of additives or co-solvents to the SOTA electrolyte.2-3 Hereby, the electrolyte decomposition can be minimized when increasing the cut-off potential (beyond 4.5 V vs. Li/Li+) that prevents the increased capacity fading of the battery. Furthermore, phosphorus (III and V) fluorinated or non-fluorinated compounds have been the subject of an investigation and can be featured as effective flame retardants.2-3 With the advance demand of energy in the last decades, an increase in the energy density, as well as an improvement in safety concerns are highly required for the advanced batteries, tailored for targeted application.2-5

In this work, several fluorinated cyclic phosphorus-based containing compounds were designed, synthesized and investigated as bifunctional - high-voltage and flame retardant – additives/co-solvent as electrolyte components for advanced LIB application. The selected molecules were correlated in respect to their structure-reactivity relationship and characterized by means of carefully selected physicochemical, electrochemical, analytical and structural methods. Furthermore, the influence of the fluorinated cyclic phosphorus-based additives/co-solvents on the overall performance of the graphite/NCM111 cells was studied. In addition, the flammability of electrolyte formulations were investigated. The results obtained from self-extinguishing time test (SET) and flash point determination, as well as TGA and DSC measurements were correlated to theoretical calculations to understand the mechanism of the combustion.

This systematical approach allows to understand the structure-reactivity relationship of the selected compounds, their impact on the overall battery chemistry, performance and safety and helps, to further tailor the properties of electrolyte additives/co-solvents for specific application.

1 D. Gao, RSC Adv. (2015), 5, 17566.

2 K. Xu, Chem. Rev. (2004), 104, 4303.

3 K. Xu, Chem. Rev. (2014), 114, 11503.

4 S. S. Zhang, J. Power Sources (2006), 162, 1379.

5 M. Asif, Renew. Sustainable Energy Rev. (2007), 11, 1388.
The Effect of Pore Connectivity on Li Dendrite Propagation within Llzo Electrolytes Observed with Synchrotron X-Ray Tomography
Authors: Hatzell Kelsey B , Dixit Marm , Shen Fengyu , Xiao Xianghui
Published: February 2020

Li7La3Zr2O12 (LLZO) is a garnet type material that demonstrates promising characteristics for all solid-state battery applications due to its high Li-ion conductivity and its compatibility with Li metal1,2. The primary limitation of LLZO is the propensity for short-circuiting at low current densities3. Microstructure features such as grain boundaries, pore character, and density all contribute to this shorting phenomenon. Toward the goal of understanding structure-processing relationships for practical design of solid electrolytes, the present study tracks structural transformations in solid electrolytes processed at three different temperatures (1000, 1050 and 1150 °C) using synchrotron x-ray tomography4. A sub volume of 300 μm3 captures the heterogeneity of the solid electrolyte microstructure while minimizing the computational intensity associated with 3D reconstructions. While the porosity decreases with increasing temperature, the underlying connectivity of the pore region increases. Solid electrolytes with interconnected pores short circuit at lower critical current densities than samples with less connected pores.

[1]Thompson, Travis, et al. "Tetragonal vs. cubic phase stability in Al–free Ta doped Li 7 La 3 Zr 2 O 12 (LLZO)." Journal of Materials Chemistry A 2.33 (2014): 13431-13436.

[2] Sharafi, Asma, et al. "Characterizing the Li–Li 7 La 3 Zr 2 O 12 interface stability and kinetics as a function of temperature and current density." Journal of Power Sources 302 (2016): 135-139.

[3] Cheng, Eric Jianfeng, Asma Sharafi, and Jeff Sakamoto. "Intergranular Li metal propagation through polycrystalline Li 6.25 Al 0.25 La 3 Zr 2 O 12 ceramic electrolyte." Electrochimica Acta 223 (2017): 85-91.

[4] Hatzell, Kelsey B., et al. "Direct observation of active material interactions in flowable electrodes using X-ray tomography." Faraday discussions 199 (2017): 511-524.

Figure 1
Quantitative Analysis of Overcharge Event in Lithium-Ion Batteries
Authors: Kobayashi Yo , Miyashiro Hajime , Mita Yuichi
Published: February 2020

Safety assessments of lithium-ion cells have been estimated by the judgment of the possibility of explosion and/or ignition of the tested cells. However, existing judgment of the safety is mainly based on the qualitative assessment so that quantitative evaluation approach is required. We developed a forced destruction system in which pressure change in event can quantitatively estimate using a pressure tight housing surrounding the test cell. We report the comparative results of the overcharged tests using LiFePO4/Graphite (LFP/Gr, 64 Wh), LiNi0.8Co0.15Al0.05O2/Gr (NCA/Gr, 15 Wh), and LiCoO2/Li4Ti5O12 (LCO/LTO, 10 Wh) systems. The increase in pressure (DPe) at overcharged state reflected well the electrode chemistry. DPe of the LFP/Gr system (2.6 kPa/Wh) was lower than that of the NCA/Gr system (7.0 kPa/Wh). The difference was derived from the cathode stability at the overcharge state. DPe of the LCO/LTO system (4.6 kPa/Wh) was lower than that of the NCA/Gr system. The stability of the LTO anode contributed the lower DPe of the LCO/LTO system than that of the NCA/Gr system. As presented above, we can quantitatively estimate the abuse event of the lithium-ion batteries with various chemistries and capacities by using developed forced destruction system.
A Macroscopic Model to Describe the Composite Effects of a LiFePO4 PVDF/Csp Cell Based on Effective Transport Parameters
Authors: Mendoza Santos Ilda Olivia , Vazquez-Arenas J. , González Ignacio , Castillo Araiza Carlos Omar
Published: February 2020

Li-ion batteries have been positioned like one of the best storage devices today there is a satisfactory combination of electrodes and electrolytes to be used for rechargeable Li-ion batteries in the electronic market due to their high energy densities (e.g. portable media, computers and small equipment), however, it is overriding to account for numerous problems related with transport mechanisms of charge and mass that significantly affect their capacities and power. The understanding of these mechanisms is complex due to various kinetic and transport phenomena interacting within the battery, and the difficulty of estimating local variables such as concentrations, potential, among other.

Mathematical modeling based on porous electrode theory [1] has been a powerful tool to understand and optimize the functioning performance of these devices. Nevertheless, the role of each component in the porous matrix of the electrode has not been accounted for since under this perception the battery is described as a whole identity [2, 3]. In this direction, the effect of electrode composition (i.e. variation of active and inactive material) on rate capabilities cannot be explained by these models.

In the present work, a macroscopic model is proposed relying on the assumption that the electrode is a porous solid matrix where active and inactive components should be separately expressed but interacting in solid and liquid phases. This enables to account for the experimental discharge of a semi cell Li °/1M LiPF6 in 1:1:1 EC:DMC:EMC/LiFePO4:PVDF-Csp considering effective transport parameters and the kinetic proposal taking in count the active material fractionin the cathode composition.

Acknowledgements:

I. Santos is grateful to CONACYT for the scholarship granted to pursue his doctoral studies.

References:

[1] Newman, J. and W. Tiedemann, AIChE Journal, 21 (1975) 25-41

[2] West, K., T. Jacobsen, and S. Atlung, Journal of The Electrochemical Society, 129 (1982) 1480-1485

[3] Farkhondeh, M., et al., Physical Chemistry Chemical Physics, 16 (2014) 22555-22565.
Large-Scale First-Principles Simulation on Li-Intercalated Graphite
Authors: Nakata Ayako , Miyazaki Tsuyoshi , Sodeyama Keitaro
Published: February 2020

Lithium-ion batteries (LIBs) have attracted considerable attention for use in larger power sources like electric vehicles and energy storage system because of their high energy densities. In the LIB, carbon materials, such as highly oriented pyrolytic graphite (HOPG), are used as negative electrode. During the charge and discharge cycle, Li-ions are intercalated to the graphite. For the Li- ions intercalation into the layered graphite, phase transition between different staging structures occurs. At first, Li-ions are intercalated randomly to whole layers, called dilute stage1. Next, stage transformation between dilute stage 1 and stage 4, stage 4 and stage 2, stage 2 and stage 1 proceed. This stage transformation plays an important role for the LIB performance, especially the maximum capacity and charge discharge rate of batteries. Regarding atomic scale mechanism of the stage transformation, Daumas and Hérold model was proposed. In the model, fully occupied and empty region of Li-ions in the layers exist, but the layers can be distorted to localize the Li-ion occupied region. This layer distortion is the key for the stage transformation. To clarify this mechanism from the view point of the first-principles study, large-scale calculations is required.

In this study, we investigate the atomic and electronic structures of Li-intercalated graphite by using our large-scale DFT program CONQUEST [1]. The CONQUEST code uses real-space local orbital functions to express density matrices instead of the plane-wave basis. Especially, recently-developed “multi-site method” [2] reduces the number of local orbital basis functions to be minimal size keeping high accuracy, which reduces the computational cost dramatically and enables us to treat large systems containing 10,000+ atoms. The comparison of the geometries and electronic structures of Li-intercalated graphite at several stage structures with several thousand atoms (as in figure 1) will be discussed in the presentation.

[1] http://www.order-n.org/

[2] A. Nakata, D. R. Bowler, T. Miyazaki, Phys. Chem. Chem. Phys. 17, 31427 (2015).

Figure 1. Large-scale simulation model of Li-intercalated graphite (stage1).

Figure 1
Effects of the Composition on the Effective Transport Coefficients of a LiFePO4 Cathode
Authors: Hernandez-Rodriguez Roel , Mendoza Santos Ilda Olivia
Published: February 2020

The LiFePO4 as cathode material for Ion Lithium batteries has been extensively studied. One of the main research interest lays on determining of charge and mass transport and their influence on specific capacity of the battery. Recent studies, the composition of the cathode slurry has been reported to influence battery performance and rate capability [1,2, 3]. However, in most studies based on effective medium equations, the intrinsic properties of each of the cathode constituents have been neglected. In this work, the effect of the composition on the geometrical and transport properties in a LiFePO4 cathode is studied theoretically and experimentally. To carry out this, an effective medium model is developed, using the volumetric averaging method. This alternative allows to theoretically predict the effective medium coefficients through a closure problem [4]. The solution of closure problems is carried out in representative samples of the porous cathode obtained by Scanning Electron Microscope (SEM). The theoretical predictions of the effective coefficients show good fit with those obtained experimentally, where it can be seen that there are deviations between the coefficients when taking into account the properties of the additional materials that make up the LiFePo4 cathode material. With this first stage of our results we have the possibility to analyze the behavior of the LiFePO4 cathode.

Guzman, G., et al., Electrochimica Acta 247 (2017) 451-459

Gao, F. and Z. Tang, Electrochimica Acta, 53 (2008) 5071-5075.

Liu, H., et al., 159
(2006) 717-720.

Whitaker, S. (1999) The Method of Volume Averaging. ISBN 0-7923-5486-9
3-D Printing with Carbon Nanotube Composites
Authors: Farthing Tyler , Mukherjee Santanu , Singh Gurpreet
Published: February 2020

The mechanical benefits gained from using carbon nanotubes in liquid thermosetting resins gives stereolithograhy 3-D printing a promising future in the world of additive manufacturing. There are some challenges faced with obtaining consistent results in this area of research, however. The primary reason is due to the unique aspect ratio of the carbon nanotubes which leads to uneven distribution during the preparation of the polymer matrix composite. Furthermore, it is also difficult to achieve complete photo-polymerization of the part due to the carbon nanotubes interference with the UV light during the curing process.

Here the effect of MWCNT filler on mechanical strength and stiffness of 3-D printed polymer-matrix composite using stereolithography printer is studied. MWCNTs were de-agglomerated in Toluene and introduced into photopolymer resin at various weight loadings. 3-D printing was performed with the composite resin followed by uniaxial tensile testing to obtain data to analyze for possible mechanical stress and strength benefits. This work concluded that the addition of .005 weight % of MWCNT showed an improvement of 24.8 % and 9.6 % for stress failure and Young’s Modulus respectively compared to neat sample. The addition of 0.01 and 0.02 weight % had adverse effects of lowering the Young’s Modulus and causing stress failure.
(Invited) Morphological Diversity and Space-Recognition of Polysaccharide Microfibers on Evaporative Interface
Authors: Okeyoshi Kosuke , Tongsuk Kittiphong , Yamashita Miki , Budpud Kulisara , Shinhama Takeshi , Joshi Gargi , Okajima Maiko K , Kaneko Tatsuo
Published: February 2020

The geometric structures of soft materials can be controlled on the macro-scale by using interfacial or mechanical instability, e.g.fingering patterns of viscous liquids and buckling patterns of gels during swelling/deswelling. These patterns can be used as smart materials for capturing/releasing and mass-transportation applications. Here we introduce the emergence of uniaxially oriented membranes by drying an aqueous liquid-crystalline solution, composed of megamolecular supra-polysaccharides, sacran, in a limited space. In addition, by controlling the geometry of the evaporation front, multiple nuclei emerge that grow into vertical membraneswith uniaxial orientation. Notably, the membrane, composed of microfiber, is rationally formed along the dynamic three-phase contact line. As a result of the self-organization, the membrane macroscopically partitions the three-dimensional cuboid cell. We envision that such uniaxially oriented membranes, obtained through partitioning phenomena, can be used as soft biomaterials, like anisotropic dialysis membranes with directional controllability in the medical and pharmaceutical field.
(Invited) Using Biomolecules to Trigger Hydrogel Shape Change
Authors: Schulman Rebecca
Published: February 2020

Shape-changing hydrogels that can bend, twist, or actuate in response to external stimuli are critical to soft robots, programmable matter, and smart medicine. We show how specific DNA molecules can induce 100-fold volumetric hydrogel expansion by successive extension of cross-links. Up to centimeter-sized gels containing multiple domains that undergo different shape changes in response to different DNA sequences can be photopatterned. DNA molecules can be coupled to molecular sensors, amplifiers, and logic circuits. Using this coupling, soft devices that respond to diverse biochemical inputs and autonomously implement chemical control programs are developed.
Microfabrication of High-Strength Gels with a 3D Printer
Authors: Takamatsu Kyuichiro , Khosla Ajit , Kawakami Masaru , Furukawa Hidemitsu
Published: February 2020

Using 3D printer Acculas, we fabricated a high-intensity particle double network gel (P-DN gel) . In this apparatus, the spot diameter of the UV laser to be irradiated can be set to 30 to 300 μm and the z pitch can be set to 30 μm at minimum. The data used was mesh of size 250 μm and the set value of spot diameter was 30 μm. The line width of the mesh was investigated by increasing the weight percentage of the UV absorber2-Hydroxy-4-methoxybenzophenone-5-sulfonic Acid Hydrate (Kemisorb 11 S) in the material composition to 0.02 to 0.06 wt%. The mesh with an average width of 89.3 μm could be fabricated with 0.04 wt% UV Absorber. It was nearly three times the set value and a variation of ± 20 μm was observed. This is thought to be the influence of the amount and particle size of the gel particles. From this result, We showed the possibility of forming a gel having a three-dimensional structure of 100 μm or less. In the future, in addition to improving modeling accuracy by adjusting material composition, we will develop new devices aiming at further miniaturization. We also plan to develop research into soft robots and modeling and evaluation of organ models.

Figure 1
Self-Healing Supramolecular Hydrogel: Polyrotaxane Cross-Linked By Host-Guest Interactions
Authors: Kobayashi Yuichiro , Takashima Yoshinori , Yamaguchi Hiroyasu , Harada Akira
Published: February 2020

Self-healing materials, which can extend the service life of objects, have attracted much attention in efforts to create a sustainable society. One of the most important approaches to obtain self-healing materials is non-covalently bonded systems. Unlike covalently bonds, non-covalent interactions such as hydrogen bonds, π-π stacking interactions, metal-ligand coordination bonds, and host-guest interactions [1] are reversible. It has been recently reported that materials recover their original mechanical property when they are damaged. This self-healing property occurs by introducing a non-covalent interaction site into the end or side chain of a polymer. In this regard, the healing time is affected by the mobility of the polymer chain because self-healing occurs by the formation of non-covalent bonds between the responsible sites via non-covalent interactions in the polymer. To address the expected practical demands and requirements, the development of a self-healing material that recovers in a short time is in high demand.

For this purpose, we employ polyrotaxanes (PRxs), which are a class of supramolecular threaded macromolecules in which cyclic molecules are threaded onto linear polymers.[2] The advantage of PRxs is that threaded cyclic compounds are freely mobile along the linear polymer because they are non-covalently assembled between the linear polymer and many cyclic molecules. Thus, compared to functional groups conjugated to a conventional polymer side chain, the functional group conjugated with the cyclic molecules in PRx can effectively bind to the target.

Herein we report a self-healing material based on PRx through host-guest interactions. This material was prepared by radical copolymerization of acryl amide (AAm) and the host monomer in the presence of PRx introduced with guest molecules. The resulting material exhibits a self-healing property, and its healing speed is faster than a self-healing material without PRx.

[1] (a) T. Kakuta, Y. Takashima, M. Nakahata, M. Otsubo, H. Yamaguchi, A. Harada, Adv. Mater. 2013, 25, 2849-2853. (b) M. Nakahata, Y. Takashima, A. Harada, Macromol. Rapid. Commun. 2016, 37, 86-92.

[2] (a) Y. Kobayashi, Y. Nakamitsu, Y. Zheng, Y. Takashima, H. Yamaguchi, A. Harada, Chem. Commun. accepted (b) A. Harada, J. Li, M. Kamachi, Nature
1992, 356, 325-327.

Figure 1. (a) Chemical structures of Ad(x)DMEDAPRx–βCD gel, Ad(x)–βCD gel, and AAm(x) gel. (b) Schematic illustration of the self-healing feature of Ad(x)DMEDAPRx–βCD gel. Here, x represents the mol% of the cross-linking unit.

Figure 1
Study of Gelation for Biodegradable Polyelectrolytes By a Counter Ion Exchange Approach
Authors: Saito Keita , Yano Shigekazu , Fukushima Kazuki
Published: February 2020

Cationic polymers are promising as a new class of antimicrobials to combat a threat of emerging drug-resistant superbugs because multiple positive charges are effective in electrostatic interaction with negatively charged bacterial cell membranes, which leads to membrane disruption.1) Since this mechanism is fundamentally different from those of most conventional antibiotics that target inhibition of an intracellular function of bacteria, these antimicrobial polymers are believed not to contribute to development of drug resistance. Originating from the first report by Nederberg et al.,2) a series of biodegradable antimicrobial polycarbonates have been developed, and biodegradability and bioabsorbability have been recognized important for antimicrobials that injection into the body is assumed. We also have recently developed cationic antimicrobial polycarbonates tagging primary ammonium salts and a hydrophobic moiety at the side chains. These polymers exhibit antimicrobial activity and biocompatibility tuned by sequence, composition, and structure of hydrophobic comonomer units.

Moreover, microbial colonization and biofilm formation on biomedical implants and devices are now acknowledged as a more severe threat and cause financial challenges for patients. Bacterial biofilm comprising complex exopolysaccharides matrix is difficult to destroy and thus serves as barriers against antibiotics. Antimicrobial hydrogels are envisioned to be an effective weapon to counter the biofilm problem.3) Biodegradable antimicrobial hydrogels are the current focus of our research because they are expected to be used for both inside and outside of the body, e.g., wound dressings for burn treatment and surface treatment of long-term implants such as catheters.

In this study, we report a simple yet effective approach to generating charged biodegradable hydrogels using a counter anion exchange approach. By using di- or tri-carboxylic acids as a counter anion for a cationic ammonium group as well as a cross-linker, a cationic polymer network may be formed. Preliminary, we have already been successful to switch a counter carboxylate of the cationic polycarbonate. To form hydrogels, physical cross-linking points and balance of (de)hydration should be rationally controlled. Thus, we explore several combinations for cationic copolycarbonates with different compositions and hydrophobic side chains and di- and tri-carboxylic acids as shown in Figure 1. In addition, a chemically crosslinked cationic polycarbonate is examined for comparison.

1) Palermo, K. Kuroda, Appl. Microbial. Biotechnol. 2010, 87, 1605-1615.

2) Nederberg et al., Nature Chem. 2011, 3, 409-414.

3) Li et al., Angew. Chem. Int. Ed., 2013, 52, 674-678.

Figure 1
(Invited) Soft Electronics and Machines with Tough Hydrogels
Authors: Kaltenbrunner Martin
Published: February 2020

Introducing methods for instant strong bonding between hydrogels and antagonistic materials – from soft to hard – allows us to demonstrate elastic, yet tough biomimetic devices and machines with a high level of complexity [1]. Tough hydrogels strongly attach, within seconds, to plastics, elastomers, leather, bone and metals reaching unprecedented interfacial toughness exceeding 2000 J/m2. Our approach is applicable in rapid prototyping and in delicate environments inaccessible for extended curing and cross-linking. The combination of ionic hydrogels with antagonistic materials such as elastomers, polymers and metals allows to create soft electronics and hybrid machines. We demonstrate stretchable batteries for self-powered soft devices, adaptive lenses, and autonomous electronic skin for triggered drug delivery (Figure 1). We further introduce a new family of biodegradable hydrogels that are able to self-heal and are resistant to dehydration. Soft machines and robots – built from hydrogels with tuned mechanical properties – are designed to be operated in ambient conditions and degrade after use. Besides progressing standalone soft machines, our advances in the synthesis of biodegradable hydrogels bring bionic soft robots a step closer to nature.

[1] D. Wirthl, R. Pichler, M. Drack, G. Kettlgruber, R. Moser, R. Gerstmayr, F. Hartmann, E. Bradt, R. Kaltseis, C. M. Siket, S. E. Schausberger, S. Hild, S. Bauer, M. Kaltenbrunner, „Instant tough bonding of hydrogels for soft machines and electronics”, Science Advances, 3(6), e1700053 (2017).

Caption Figure 1: Hydrogel electronic skin. (left) Concept of a hydrogel smart skin, with a flexible unit bearing power supply, control, readout and communication units, and a stretchable transducer batch. (right) Photograph of an untethered electronic hydrogel with four stretchable heating elements and adjoined temperature sensors strongly bonded to a PVA hydrogel. Battery, control, readout and Bluetooth Low Energy communication electronics are hosted on a flexible circuit board.

Figure 1
(Keynote) Textile-Enabled Wearable Energy Devices
Authors: Zheng Zijian
Published: February 2020

Wearable electronics is foreseen to be the next major technology after smart phone in the near future. However, most conventional electronic devices are rigid, bulky, and heavy, making them difficult to wear. On the other hand, textiles are materials that have been worn by human beings for more than a thousand years. Textiles are flexible, lightweight, conformal, and highly manufacture-able. This talk will introduce how our research group makes use of fibre and textile for wearable electronics. These fibre-based electronic devices can function as high-performance electronics while maintaining the flexibility, lightweight, permeability, processibility, and even washing ability like textiles. In addition, we also show that fibre-based device can significant improve the electrochemical properties of the devices.

References:

[1] Q. Huang, D. Wang, Z. J. Zheng*, Adv. Energy Mater. 2016, DOI: 10.1002/aenm.201600783.

[2] L. Liu, Y. Yu, C. Yan, K. Li, Z. J. Zheng*, Nat. Commun. 2015, 6, 7260.

[3] Y. Yu, C. Yan, Z. J. Zheng*, Adv. Mater. 2014, 26, 5508­5516.

[4] Y. Yang, Q. Huang, L. Niu, D. Wang, C. Yan, Y. She, Z. J. Zheng*, Adv. Mater. 2017, 160667
(Invited) 3D Monolithic Integration in Flexible Organic Printed Transistors
Authors: Jung Sungjune
Published: February 2020

Despite the significant enhancements in material properties such as carrier mobility, few attempts have been made to print organic integrated circuits (ICs). The relatively large size of printed features (typically 10 μm – 100 μm) have limited the implementation of organic ICs with reasonable transistor densities. To overcome the limitation, we introduce three-dimensional (3D) integration of inkjet-printed organic transistors and circuits. We fabricated a p-type organic field-effect transistor that is inkjet-printed on top of an n-type organic field-effect transistor with a shared gate joining the two transistors. Based on the common-gate transistor-on-transistor structure, a complementary inverter array is fabricated with a high static noise margin and reliable characteristics. We have further developed 3D integration of a dual-gate NAND technology fabricated by printing technique with a demonstration of flexible logic circuits. The vertical stacking of independent-gate controlled dual gate transistors offers enhanced on-current, lowered sub-threshold swing, increased device stability and density. The present study fulfills the essential requirements for the fabrication of organic printed complex ICs, and the findings can be applied to realize more complex digital/analogue ICs and intelligent devices
(Keynote) Controlling Size and Dispersity in Nanoparticle Synthesis: Some Theoretical Results
Authors: Schmid Friederike
Published: February 2020

Polymeric nanoparticles are of increasing interest in nanotechnology and nanomedicine. One promising approach to preparing nanoparticles in a controlled manner is self-assembly from solution, e.g., in microfluidic devices. Molecular parameters such as the polymer length and architecture as well as process parameters such as mixing speed and shear rate can be used to control the size and shape of the particles.

Here we use self-consistent field theory and field-based simulations to investigate some of the main physical mechanisms underlying this control. The talk will have two parts.

In the first part, we examine the influence of molecular parameters on the resulting particles, with particular focus on the effect of molecular dispersity. Traditionally, theoretical studies us model systems of idealized monodisperse polymers. In reality, however, most synthetic polymers are inherently polydisperse, and this has a significant impact on the size and dispersity of the nanoparticles.

In the second part, we examine mechanisms of size control by tuning process parameters. We examine the so-called co-solvency method, where a collapse of polymeric nanoparticles from solution is induced by mixing bad solvent into a polymer dispersion. Experimentally, it is found that the particle size can be tuned by varying the mixing speed. We show that this control essentially happens in the initial stage of polymer-solvent demixing and derive scaling laws which are in agreement with experiments. Then, we study the effect of high shear rates on self-assembly. Shear mainly affects the later stages of self-assembly. It can reduce potential barriers for particle fusion and thus assist the production of larger particles. Furthermore, it can induce irreversible shape changes and be exploited to make particles with unconventional shapes.