bluuebunny/crossref_metadata_2025 huggingface dataset:
Challenging the Limits of Nanoscale Simulations: Modeling Joule Effect and Piezoresistivity in Carbon Nanotubes Enforced Polymers
Authors: Donati Greta , Milano Giuseppe
Published: February 2020

The unique electric properties of carbon nanotubes (CNT)1, have opened new scientific and technological fields2 based on the investigation and optimization of CNT filled polymers3. CNTs, when added to polymer matrices (such as epoxy, bitumen, concrete) make them conductive once they overcome a specific (so-called percolative) concentration4. When this percolative threshold is reached, a CNT electric circuit is formed and the composite materials become conductors. Based on such peculiar behavior, smart materials able to monitor their own conditions could be realized and employed for several applications ranging from automotive and aeronautics to civil engineering infrastructures.

The main goal of this work is to understand, through a theoretical-computational approach, the electric behavior of CNT based composites5 and help in improving their performances. In particular, the Joule effect, i.e. the heat dissipation of the conductive CNTs is simulated. The CNTs Joule effect can be employed to build smart materials able to have specific properties (i.e. self-deicing under certain temperatures) or to repair their own cracks (self-healing). The piezoresistivity, i.e. the change in the electric resistance of the CNTs due to an applied strain or stress, is also investigated. This feature allows these composites to be sensitive to an external stress or damage (self-sensing), in this way an immediate and efficient repair can be performed.

A computational protocol to understand the behavior, the sensitivity and the limits of such materials at the nanoscale is proposed. This will improve the materials performances and efficiency on larger scales. For the first time, a computational modeling strategy along with preliminary results is built and presented to simulate at the nanoscale the Joule effect and the piezoresistivity of CNTs filled polymers. Obtaining a widely applicable strategy to model electric properties of CNTs and characteristic behavior trends of such materials is the final goal of this project.

[1] Iijima, Nature, 1991, 354, 56-58.

[2] W. Nan, Y. Shen, J. Ma, Annu.Rev.Mater.Res., 2010, 40, 131-151.

[3] M. Ajayan, O. Stephan, C. Colliex, D. Trauth, Science, 1994, 265, 1212-1214.

[4] M. Mutiso, K. I. Winey, Prog. Polym. Sci., 2015, 40, 63.84.

[5] Zhao, M. Byshkin, Y. Cong, T. Kawakatsu, L. Guadagno, A. De Nicola, N. Yu, G. Milano, B. Dong, Nanoscale, 2016, 8, 15538-15552.
Effect of Molding Condition on Mechanical Properties in Injection and Compression Hybrid Molding
Authors: Nakai Asami , Funahashi Masahiro
Published: February 2020

The advantage for discontinuous fiber reinforced thermoplastic composite is to form a complicated shape in a short time. On the other hand, the continuous fiber reinforced plastic (c-FRTP) has high mechanical properties, but its process ability is limited and it is difficult to produce complicated shapes such as ribs. Therefore, the hybrid molding method attracts attention.

The hybrid molding method used in this study is a molding method combined the compression molding with continuous fiber and the injection molding with discontinuous fiber. Hybrid molding is a method of injecting and joining discontinuous fibers to a continuous fiber part. The part of requiring strength is formed by compression molding of intermediate material with continuous fiber, and the complicated shape part is made by injection molding of discontinuous fiber.

However, there is a problem with the strength of the joint part between the intermediate material part molded by compression molding and the part molded by injection molding. Joining characteristics are affected by preheating conditions of c-FRTP, molding conditions such as temperature, pressure and speed of injection resin. Therefore, it was aimed to clarify the effects of the preheating condition for the intermediate material and the temperature of the injection resin on the mechanical properties of the molding and injection resin joint.

In this research, a hybrid molding machine of a press machine and an injection machine was used. A heating test was conducted by using preheating devices, and the temperature distribution and the difference in temperature rise were investigated. In addition, the influence of the difference in the preheating condition of the intermediate material on the strength was examined by evaluation of mechanical properties, surface and cross sectional observations. From this study, middle infrared was found out to be the most suitable preheating device for hybrid molding, from its advantages that could preheat in a short time and improves mechanical property.
Al-Doped ZnO Nanotubes Designed Via Simultaneous Doping and Etching of H2o-Oxidized ZnO Nanorods for Perovskite Solar Cells
Authors: Pelicano Christian Mark , Yanagi Hisao
Published: February 2020

Herein, a novel approach to generate Al-doped ZnO nanotubes (AZO NTs) via simultaneous doping and etching of H2O-oxidized ZnO nanorods (NRs) is presented. The simultaneous doping and etching was done through a facile one-step spin-coating process of a methanolic AlCl3 solution on top of the NRs. The acidic nature of the AlCl3 solution triggers the selective etching of polar (001) planes of ZnO resulting in the formation of NTs. At the same time, doping with Al occurs. Surface morphological analysis revealed the gradual transformation of the NRs to full NTs with increasing number of AlCl3 coatings. Improved transmittance and a blue shift in absorption edge can also be observed in doped films indicating band gap broadening. Evidence of dopant inclusion in AZO NTs was verified in XPS measurements. XRD and Raman spectra displayed a shift in 2
θ values and reduced E2 peaks for the AZO NTs, respectively. These results also demonstrate the successful incorporation of Al3+ ions in ZnO crystals. In addition, room temperature photoluminescence showed that all the samples exhibited blue (l = 450 nm) and orange emissions ((l = 650 nm); however, the intensity of the latter emission is reduced and a new green emission ((l = 530 nm) appeared with the increase in Al concentration. Moreover, the AZO NTs exhibited higher electrical conductivity and electron mobility values compared with undoped ZnO NRs. These improved electrical properties, as well as, the higher surface area of AZO NTs could substantially enhance the photovoltaic performance of perovskite solar cells through effective electron extraction and suppression of carrier recombination. Finally, we are now aiming to utilize these films as electron-transporting layer for perovskite solar cells.

Figure 1
(Invited) Organic and Inorganic Materials for Efficient Pb and Pb-Free Perovskite Solar Cells
Authors: Wakamiya Atsushi
Published: February 2020

Perovskite solar cells have attracted much attention as cost-effective next generation printable photovoltaics. In a relatively short period, power conversion efficiencies in such cells have been substantially increased, mainly due to improvements of the fabrication protocols for the perovskite layer as well as the development of new materials for buffer layers.

Our approaches toward efficient lead and lead-free perovskite solar cells are as follows.

1) Development of organic semiconductors as efficient charge-collection layer: We design and synthesis of novel p-conjugated materials in terms of control of the energy level of frontier orbitals and molecular aggregation.

2) Development of highly purified perovskite precursor materials: We synthesis of a series of complexes of lead halides or tin halides as purified precursor for perovskite materials.

3) Development of fabrication methods for perovskite layer by solution process: We focus on the intermediates formed during the solution process and develop efficient fabrication methods based on the mechanism.

In this talk, we introduce our recent progress on tin halide perovskite solar cells as well as lead halide perovskites.
Improving the Dye Loading of TiO2/MWCNT Composite Based Dye Sensitized Solar Cells By Vacuum Assisted Dye Adsorption Technique
Authors: Naveen Kumar S K , Kiran S
Published: February 2020

The most attractive properties of Dye Sensitized Solar Cells (DSSCs) are their low cost and simple manufacturing processes which makes them as one of the promising third generation solar cells. Each part of the device and the fabrication process heavily determines the cost and efficiency. Dye loading is such one process where the dye sensitizers are made to adsorb on the surface of the mesoporous TiO2/MWCNT nanocomposites. The type of the dye, situations and time of dye loading plays a vital role in performance of the DSSCs. This work reports the synthesis of TiO2/MWCNT nanocomposite and its structural characterization done using Field Emission Scanning Electron Microscope (FESEM) and BET surface area analyzer. Photoandoes were prepared by doctor blade technique with a thickness of 21µm. The dye loading process in ambient condition and in a self developed low cost set up to load the dye under vacuum are compared. The work also reports effects of dye loading time on the amount of dye loaded, chemical stability of photoanode and the light conversion efficiency of the DSSCs. It was seen that dye adsorption increased by 29.6% when loaded in vacuum compared to normal loading conditions. Over all time required to reach the saturated level of dye adsorption was decreased to 8 hours from 18 hours of soaking in ambient conditions.
Materials Challenges for Energy Storage/Conversion Applications
Authors: Manivannan Mani
Published: February 2020

Among the goals of modern renewable energy systems is to convert the available resources into clean forms of stored energy to alleviate the crisis of fossil fuel exhaustion and oil dependence for energy production. New energy storage and conversion technologies are needed for the development of a cost-efficient renewable energy sources. Materials are the key to fundamental advances in various such energy conversion and storage applications. ln order to meet the challenge of global concerns on pollution and the existing fossil fuels it is important to develop new conversion and storage devices. Especially, materials with unique nanostructures offer exceptional properties or combinations of properties for a wide range of energy devices. This presentation will review/describe some of the recent developments in materials for batteries, supercapacitors, fuel cells, photoelectrochemical cells etc. Novel current and emerging electrode materials and their processing methods for battery technologies based on Lithium, Magnesium, Sodium etc., various carbon/transition metal oxide composite, nitride-based supercapacitors and OER (oxygen evolution reaction) catalysts for advanced air batteries and fuel cells will be presented. The advantages of the nanoscale in materials design for such devices and possible new pathways for improving the strategy of the materials design will be discussed.
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 and 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 and 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.
Study of Active Center Structures for Fe/N/C Type Oxygen Reduction Catalyst Using Semi-Empirical Molecular Orbital Calculations
Authors: Shiroishi Hidenobu , Ono Ryoma
Published: February 2020

Polymer electrolyte fuel cells (PEFCs) are one of the most important devices in realizing hydrogen society. Platinum, which is used as the catalyst of PEFCs, is expensive and less abundant. Thus, the development of a non-platinum oxygen reduction catalyst is required for the wide-spread use of PEFCs. Fe/N/C non-platinum oxygen reduction catalysts are promising platinum alternative catalyst candidates. We have reported new metal/nitrogen/carbon-electrocatalysts synthesized by the pyrolysis of precursors consisting of Ketjenblack®, a Zn complex with 4,4’-bipyridine, 1,10-phenanthroline (phen), and iron(II) chloride1)．The density of active sites on the catalysts need to be increased for the improvement of for oxygen reduction reaction (ORR). Although we obtained that pyridine type nitrogen is related to the ORR activity, the chemical structure of the active center is still unknown. The conclusion does not match whether Fe atoms function as activity centers2-3．In this study, the structures of active center for Fe/N/C ORR catalysts were studied using semi-empirical molecular orbital calculations．

Assuming that four electrons were injected into the compound, the distance between an O2 molecule and atoms was stepwise shortened with the parameters4 using MOPAC 20165. The result of the calculation was visualized by Jmol6. We used model compounds modeling a part of the edge of a graphite layer (Fig. 1(a)).

Fig. 1(b) shows the dependence of ΔH on the distance between O and target atoms during shortening distance. The activation energies of route (i) was the smallest of the four routes. The cleavage of O-O bond occurred at routes (i) and (iv). The supply of further proton via H3O+ is necessary in the route (ii) and (iii).

References and Notes

Shimbori, H. Shiroishi, R. Ono, S. Kosaka, M. Saito, T. Yoshida, H. Katagiri, K. Miyazawa, Y. Tanaka, Mat. Sci. Eng. B, 228, 190 (2018).

Lefèvre, J.P. Dodelet, P. Bertrand, J. Phys. Chem. B
, 106, 8705 (2002).

Guo, R. Shibuya, C. Akiba, S. Saji, T. Kondo, J. Nakamura, Science, 351, 361 (2016).

Typical calculation parameters of MOPAC used in the simulations: PM6-DH2 EF PRECISE PULAY CAMP ITRY=9999 SHIFT=50 SYMMETRY STEP=-0.025 POINT=74 NOINTER GRAPHF EPS=78.5 NSPA=200 (UHF) CHARGE=(2 to -2).

MOPAC2016, James J. P. Stewart, Stewart Computational Chemistry, Colorado Springs, CO, USA, HTTP://OpenMOPAC.net (2016).

Jmol: an open-source Java viewer for chemical structures in 3D. http://www.jmol.org/

Figure 1
Adsorption and Desorption Properties of CeO2 Nanoparticles for Concentrating Dilute CO2
Authors: Kanahara Keita , Matsushima Yuta
Published: February 2020

A recent concern about an energy issue has encouraged investigation on photocatalytic [1] or electrochemical [2] conversion of CO2 to fuels such as methane and methanol. For the realization of the conversion of CO2 to fuels, a technique concentrating dilute CO2 in the atmosphere also becomes important. A rare-earth oxide of CeO2 is an excellent adsorbant against CO2 [3]. The advantage is that CeO2 adsorbs CO2 near room temperature and releases it until 300 °C. The mass of the CO2 adsorbed to 1 g of CeO2 reaches 0.04 g at most, although the adsorption and desorption properties are dependent on the natures of particles. The crucial factors have not been revealed yet. In this work, we prepared several CeO2 nanoparticles with different synthetic routes and characterized their properties with respect to the unit cell dimensions, morphologies, and specific surface areas. The CeO2 nanoparticles were prepared by (1) thermal decomposition of Ce2(CO3)2·8H2O or CeCO3OH, and (2) precipitation by raising the pH of Ce(NH4)2(NO3)6 aq with NH3 or CO(NH2)2. Some samples were heat-treated at 300 °C to improve the crystallinity and the effects of the heat treatment were examined.

The adsorption and desorption properties were characterized by thermogravimetric (TG) analysis (Rigaku Thermo plus EVO), in which a powder sample was pretreated in TG in dry CO2 at 250 °C to remove the adsorbed CO2 and H2O and then kept at 25 °C in CO2 for adsorption equilibrium. The mass of the adsorbed CO2 was calculated from the weight change between 25 and 250 °C.

XRD indicated the formation of fluorite type CeO2 regardless of the preparation routes. TEM observation revealed that the prepared samples were composed of nano-sized particles less than 10 nm. The TEM observation exhibited well crystallized nanoparticles of CeO2 with clear lattice fringes in the images. The broadened XRD peaks were attributed to the smallness of the grain size. The CeO2 particles prepared via thermal decomposition of Ce2(CO3)·8H2O or CeCO3OH showed better performance on CO2 adsorption. Quite interestingly, there was no distinct correlation between the specific surface areas evaluated by N2 adsorption and the CO2 adsorption. Rather, the nanoparticles which had a specific crystallite size around 5~6 nm appeared to be advantageous on the CO2 adsorption as shown in Fig. 1. Fig. 1 shows the adsorbed mass of CO2 to 1 g of the CeO2 powders prepared via the different synthetic routes. An increasing tendency can be seen in the adsorbed mass until 6 nm when the data was plotted against the crystallite size.

[1] H. Rao et al., Nature 548 (2017) 74.

[2] S. Kaneco et al., Ind. Eng. Chem. Res. 41 (2002) 5165.

[3] C. Li et al., J. Chem. Soc. Faraday Trans 1 (1989) 3901.

Figure 1
(Keynote) Nanomaterials and Interfaces for Efficient Solar Energy Conversion
Authors: Yang Shihe
Published: February 2020

Nanostructured materials and interfaces are critical to the functioning of solar energy conversion devices. For photovoltaics, hybrid organic/inorganic halide perovskite solar cells have emerged as among the most competitive photovoltaic technologies of the future thanks to their superb and rapidly improving power conversion efficiencies (PCEs). For realistic deployment of the perovskite photovoltaic technology in large scale, however, device stability has become more and more important issue of the day. I will update our recent efforts in the material and interface innovations to develop high-efficiency and high-stability perovskite solar cells: (1) the relationship between device stability and ion movement of the perovskite layer; 2) the use of NiO and carbon nanostructures for efficient hole extraction and enhanced device stability; and 3) the development of perovskite and interface engineering techniques for improving both efficiency and stability. Implications of these results on the future development of perovskite solar cells will be discussed.

For electrocatalysts needed for generating solar fuels, I will focused on two-dimensional (2D) materials. In particular, molybdenum sulfide (MoS2) is an attractive noble-metal-free electrocatalyst for the hydrogen evolution reaction (HER). We have recently demonstrated significantly enhanced HER kinetics by controllably fabricating a stepped MoS2 surface structure. Vertical arrays of MoS2 sheets terminated with such a stepped surface structure have proved to be an outstanding HER electrocatalyst with overpotential of 104 mV at 10 mA/cm2, exchange current density of 0.2 mA/cm2 and high stability. Experimental and theoretical results indicate that the enhanced electrocatalytic activity of the vertical MoS2 arrays is associated with the unique vertically terminated, highly exposed, stepped surface structure with a nearly thermoneutral H-adsorption energy.

The HER electrocatalyst we engineered above, albeit based on the earth-abundant 2D MoS2, is only active in acidic media, and the HER reaction kinetically retarded in alkaline media. Thus, improving the sluggish kinetics for HER in alkaline media is crucial for advancing the performance of water-alkali electrolyzers. Toward this end, we have demonstrated a dramatic enhancement of HER kinetics in base by judiciously hybridizing vertical MoS2 sheets with another earth-abundant material, layered double hydroxide (LDH). The resultant MoS2/NiCo-LDH hybrid exhibits an extremely low HER overpotential of 78 mV at 10 mA/cm2 and a low Tafel slope of 76.6 mV/dec in 1 M KOH solution. At the current density of 20 mA/cm2 or even higher, the MoS2/NiCo-LDH composite can operate without degradation for 48 hr. This work not only brought forth a cost-effective and robust electrocatalyst, but more generally opened up new vistas for developing high-performance electrocatalysts in unfavorable media recalcitrant to conventional catalyst design.
(Invited) Synthetic Catalysts for Water Oxidation Using Metal Complexes and Nanoparticles
Authors: Yagi Masayuki
Published: February 2020

With solar cells, sunlight can be efficiently converted to electric power, however the electric power is instant. As soon as the Sun goes down, the electric power goes dim. On the other hand, conversion of sunlight into fuels provides a viable way of storing the sunlight for its permanent utilization. Green plants, algae, and cyanobacteria provide an efficient way of storing the sunlight in the form of sugars and starches using water and carbon dioxide (CO2) as feedstock materials by enzyme systems of high complexity in photosystems I and II in a process known as photosynthesis. The sunlight is utilized to get out electrons and protons from water via its oxidation at photosystem II with extremely high catalytic activity with turnover frequencies (TOFs) of 100-400 s-1 at overpotential (η) of only 160 mV. The electrons and protons are then siphoned off for the reduction of CO2 to sugars and starches at photosystem I.

Inspired from photosynthesis, researchers worldwide are trying to design an artificial photosynthetic device that could efficiently convert the sunlight to fuels (H2 or CO2 reduction products such as CH4, CH3OH, CO, HCOOH, …etc.) using a combination of inexpensive materials and water or water and CO2 as sustainable raw resources. Two artificial photosynthetic devices have been designed, photoelectrochemical (PEC, artificial-leaf) and photovoltaic (PV) driven electrolyzer. In both electrolyzers, water via its oxidation at the photoanode/anode is the source of protons and electrons required for the fuel production at the photocathode/cathode. Water oxidation, however, is a kinetically sluggish process because of the complexity of the reaction mechanism that involves the removal of four protons and four electrons from two water molecules to form O=O double bond It consequently requires a potential substantially higher than the thermodynamic value [E
0(H2O/O2) = 1.23 V, pH = 0], that is η, likely due to the generation of energetic intermediates in the multiple electron and proton coupling steps. The high η value complicates the design of efficient artificial photosynthetic device for fuel production. Consequently, it is crucial to develop highly efficient anodes for water oxidation to decrease η and thus realize efficient artificial photosynthetic device. Herein we report our recent progress on water oxidation catalyst of metal complexes and nanoparticles.
Nanocellulose Ionomer Membranes for Electrochemical Energy Conversion
Authors: Lyth Stephen Matthew
Published: February 2020

Nanocellulose is a promising new ionomer membrane material for polymer electrolyte membrane fuel cells (PEFCs). It is the most abundant polymer in the world, making it much cheaper than conventional ionomer membranes such as Nafion or Aquivion. It I three times stronger and has three orders of magnitude lower hydrogen permeability than Nafion. We investigated the proton conductivity and prepared the world’s first operational PEFCs with nanocellulose membranes.

In order to improve the proton conductivity, we prepared sulfonated nanocellulose. To take advantage of the low hydrogen permeability and high strength, we developed very thin membranes. Spray-painting was used to fabricate “paper fuel cells” with 8 µm-thick sulfonated nanocellulose membranes. This resulted in high current density (almost 1 A cm-2), and a maximum power density of 156 mW cm-2 (H2/air, 80°C, 95% RH, 0.1 MPa).

The cost of these spray-painted sulfonated nanocellulose membranes was calculated to be ~50 $/m2, which is much lower than e.g. Nafion. This work paves the way for the mass production of affordable, recyclable, and even disposable fuel cells.

Acknowledgements: We acknowledge the support of Q-PIT; NEXT-FC, and WPI-I2CNER (sponsored by the WPI Initiative, MEXT), Japan. This research was partially supported by the Center of Innovation Program from Japan Science and Technology Agency, JST. The work was also partially supported by JSPS KAKENHI Grant-in-Aid for Young Scientists (B), Grant Number JP17K14087.

Figure 1
Nanofibrous Inorganic Semiconductors in Electrocatalytic CO2 Reduction
Authors: Aljabour Abdalaziz , Coskun Halime , Apaydin Dogukan Hazar , Stadler Philipp , Sariciftci Niyazi Serdar , Kus Mahmut
Published: February 2020

The electrochemical carbon dioxide reduction reaction (CO2RR) is attractive in terms of resolving the ever-growing release of CO2 from anthropogenic cause. Thereby, electrochemical CO2RR combines high energy-transfer yields and the refinement to versatile products such as C1- chemicals, which represent the concurrent carbon feedstock.

Herein we explore the CO2 reducing property of nanofibrous chalcopyrite copper indium sulfide CuInS2 (CIS) and the pristine cobalt oxide (Co3O4), both p-type semiconducting materials, towards CO production mainly with remarkable faradaic efficiencies of 77% and 65%, respectively [1]. The focus in our studies are given to the utilization of the nanofiber electrodes as an appropriate electrocatalyst for CO production without using further expensive metal supplements, e.g. palladium, platinum, and potassium. Thus, the nanocrystalline shaping of nanofiber networks was achieved by the low-cost, versatile and time-saving electrospinning technique. In order to reduce the imperfection in the crystalline fiber, Polyacrylonitrile (PAN) was selected as template polymer [2]. The desired chemical structure of nanofibers was achieved through sintering process at 500 °C and 550 °C, respectively.

With reasonable product selectivity by CuInS2 and pristine Co3O4 nanofibers [3] and a stable operation at a constant electrolysis potential for many hours, we think that this work will stimulate more exploration into using nanofiber based materials in energy recovery and carbon capture and utilization technologies.

[1] Aljabour A.; Coskun H.; Apaydin D.H.; Ozel F.; Hassel A.W.; Stadler P.; Sariciftci N.S.; Kus M.; Applied Catalysis B: Environmental; 229; 2018; 163–170.

[2] Ozel F.; Kus, M.; Yar, A.; Arkan, E.; Yigit, M. Z; Aljabour, A.; Büyükcelebi, S.; Tozlu, C.; Ersoz M, Materials Letters. 2015, 140, 23–26.

[3] Aljabour A.; Apaydin D.H.; Halime Coskun, Ozel F.; Ersoz M.; Stadler P.; Sariciftci N.S.; Kus M.; ACS Appl. Mater. Interfaces 2016, 8, 31695−31701.
VUV-Assisted Photochemical Sol-Gel Processing of Metal Oxide Thin Films
Authors: Sun Lina , Kurosawa Yuu , Yoshida Tsukasa , Suzuri Yoshiyuki
Published: February 2020

Metal oxides such as TiO2, ZnO, SnO2 are useful in many of energy devices because of their high chemical stability, n-type semiconductivity and photoelectrochemical properties. Various methods of solution processing of their thin films are known, such as chemical bath deposition, electrodeposition and sol-gel reactions. Typically, high temperatures need to be applied for crystallization to achieve good properties. The need of high temperature however limits the choice of substrates to heat-resistant materials. Also, crystallization often results in pinholes and cracks to damage the performance of devices.

We have developed an alternative sol-gel method to obtain ultra-smooth thin films of various metal oxides at room temperature, by employing photochemical decomposition of coated precursor by vacuum ultraviolet (VUV) light irradiation. The method is compatible with conductive plastic film substrates, so that multiple applications in thin film devices such as transparent conductive layer, light emitter, buffer layer in solar cells and thin-film encapsulation (TFE) as an example shown in Fig. 1 can be envisioned.

Figure 1
(Invited) Diffusion Map Analysis of Multi-Channel Time Series Data
Authors: Nakamura Takashi , Hagan Scott
Published: February 2020

Sensor data often come in the form of multichannel time series, for example, ECG, EEG, and structural vibration monitoring to name a few. Conventionally, such multichannel time series data are analysed by using FFT for each channel, and/or by computing inter-channel correlations. Mathematically, however, these signals are better represented by dynamical systems, which are sets of differential equations.

The behaviour of a dynamical system may be visualised as a trajectory in the so-called phase space. For example, the state of a weight suspended by a spring can be fully described by the weight’s position x and its velocity v, hence its temporal behaviour creates a trajectory in its phase space (x, v). It works similarly for real systems that produce time series data. From a single channel of time series x(t) it is possible to reconstruct the phase space trajectory using lagged variables x(t), x(t-1), x(t-2),…., x(t-n). It is, however, very difficult to find and analyse the trajectory because the dimensionality of the phase space is very large in general.

In this presentation, we will show that a method called the diffusion map can extract the lower dimensional manifold in which the trajectory resides, and reveal the structure of the dynamics. Using some toy models we will demonstrate how our technique can be used to extract various useful information about the nature of the dynamics, including identification of anomalies, especially signs for imminent catastrophic changes such as phase transitions or structural collapse.
(Invited) Macro and Microstructure Biomimetic Hydrogel for Biotechnology
Authors: Kazi Gulsan ara sathi , Rahman Kazi Anisur , Matsumoto Takuya
Published: February 2020

In vitro fabricated biological tissue would be a valuable tool to screen newly synthesized drugs or understand the tissue development process. Several studies have attempted to fabricate biological tissue in vitro. However, controlling the growth and morphology of the fabricated tissue remains a challenge. Therefore, new techniques are required to modulate tissue growth. Advancements in biomaterial science have resulted in materials having cellular and tissue biocompatibility. Hydrogel materials have especially attracted a great deal of attention because of their unique biocompatibility, advantageous physical characteristics, and innate structural similarities to the extracellular matrix. Recent advances in hydrogel chemistries are enabling researchers to create hydrogels that can act as encapsulation of cells, 3D ex vivo tissue models, allowing them to explore fundamental questions in cell biology by replicating tissues' dynamic and nonlinear physical properties. Herein, we introduce a simple and novel 3D - printed device to prepare hydrogel beads and multi-properties gel sheet. We also prepared special hydrogel pattern for 3D ex-vivo organ culture. Regenerative medicine is a multidisciplinary field that aims to regenerate or replace diseased tissues or organs, restoring or maintaining their normal function. Given that every organ in the human body can be prone to failure or to injury, the field of regenerative medicine has expanded. Our data are invaluable in understanding how a hydrogel-based technology help us to understand the basic process of tissue development and has explored the applications of these technologies in the fields of materials science, soft robotics, biotechnology and medical treatment.

Reference:

Kazi GAS, Rahman KA, Farahat M, Matsumoto T. Fabrication of single gel with different mechanical stiffness using three-dimensional mold. J Biomed Mater Res A. 2018, ‘Accepted Article’, doi: 10.1002/jbm.a.36455.

Sathi GA, Kenmizaki K, Yamaguchi S, Nagatsuka H, Yoshida Y, Matsugaki A, Ishimoto T, Imazato S, Nakano T, Matsumoto T. Early initiation of endochondral ossification of mouse femur cultured in hydrogel with different mechanical stiffness. Tissue Eng Part C Methods. 2015; 21:567-75.

Kazi Ar, Sathi Ga, Taketa H, Farahat M, Okada M, Torii Y, Matsumoto T. Novel 3d Printed Device For The Simple Preparation Of Hydrogel Beads. 3d Printing And Additive Manufacturing. 2(1): 5-11:2015.
(Invited) Self-Synthesized Titanium Di-Oxide (Tio2) Nanoparticles Based Sensor for Brain Signals Extraction
Authors: kumar N Santhosh , Naveen Kumar S K
Published: February 2020

Titanium dioxide (TiO2) nanoparticles has been synthesized by using hydrothermal method. The effect of hydrothermal temperature and structure of the TiO2 nanoparticles are mentioned here. This paper describes the optical and structural properties of the self synthesized TiO2 nanoparticles using various characterization tools like UV-Visible spectrophotometer, X-ray diffraction, FESEM with EDAX etc, this work mainly concentrates on the MOS structure. MOS structure involves the silicon substrate as semiconductor, silicon dioxide as oxide layer, self synthesized TiO2 nanoparticles are the active layer and silver has used for contact. The electrical study for the MOS structure was carried out. Capacitance versus voltage (CV) and current versus voltage (IV) are the important characteristics has performs to conclude the MOS structure is working as sensor.

Figure 1
(Invited) Influence of Post Deposition Annealing on the Electrical Properties of Pt-Ti/HfO2/TiN/Sion/n-Si Capacitor for Flash Memory Applications
Authors: Vaid Rakesh , Rajput Renu , Khosla Ajit
Published: February 2020

To address the cell-to-cell interference in conventional floating gate (FG) ﬂash memory, a fully planar structure demands continuous scaling of poly silicon ﬂoating gate thickness. But the reduced FG thickness causes reliability issues due to ballistic current through inter-poly dielectric (IPD) and also decreases the gate coupling ratio (GCR). The introduction of metal FG in ﬂash memory eliminates the problem of poly depletion and ballistic transport even with ultrathin ﬂoating gate (<10 nm) and excellent memory performance with 16 V P/E window for 1 nm metal floating gate. Numerous studies on flash memory devices reported that a hybrid FG, transition metal dichalcogenides and multilayer graphene as FG results in improved memory performance such as fast program speed, excellent data retention and endurance characteristics. According to ITRS scaling projections for FG NAND flash, GCR of 0.6-0.7 would be desirable for satisfactory operation. However, in order to obtain adequate GCR, high-k based IPD and/or tunnel barrier has been proposed as mandatory alternatives. The improvement in GCR owed to greater coupling between the control and floating gates as a result of increased dielectric constant. The incorporation of nitrogen into tunnel oxide of NVM through nitridation can enhance the reliability performance of tunnel oxide of charge storage NVM. In this paper, we report the fabrication of Pt-Ti/HfO2/TiN/SiON/n-Si capacitor for flash memory applications with gate coupling ratio (GCR) of 0.68 and 0.71 for as-deposited and annealed SiON respectively. The XRD, AFM, FTIR, FESEM and XPS characterizations have been performed for structural and morphological studies. Program/erase and retention characteristics reveal the largest memory window of approx. 11.2 V after post deposition annealing and excellent data retention at room temperature under ±10 V. The enhanced program/erase speed was due to the fact that annealed SiON tunnelling oxide provides stronger interface against Si dangling bond generation and the decrease in barrier height of both electrons and holes. These results indicate that the SiON tunnelling oxide can be engineered by post deposition annealing for the improvement of metal floating gate memory performance.
(Invited) Suspended Graphene-Based Sensor for Real-Time and Highly Sensitive Monitoring of VOCs
Authors: Kumar Rakesh , Dang Caroline , Hadi Faisal , Sexton James , Koehne Jessica E. , Boult Stephen , Dixon Neil , Migliorato Max
Published: February 2020

Volatile organic compounds (VOCs) are emitted from solids or liquids with high vapor pressure and are often combustible and toxic, so on site real-time monitoring is vital. Currently photoionization detectors (PIDs) are used for VOC monitoring. PID devices are bulky and expensive to make and operated at high voltage to operate. As such there is a need for more portable and less expensive methods for detecting VOCs. We developed a novel gas sensor for (VOCs) detection. This technology utilizes suspended graphene membranes to provide real-time, ultrasensitive VOC detection. A freestanding graphene film suspended over an array of cavities or trench can offers increased surface area (twice over) and gives a direct method of sensing when VOCs adsorbed at the surface of graphene. Our sensor requires low voltages to operate, immediate response, high sensitivity and a larger theoretical range of detection than photoionization detectors sensors and it is a non-specific as PIDs.

In this work, we shall present a 3 mm X 3 mm square chip, fabricated using conventional photolithography, containing an array of two terminal devices. Each individual device consists of a monolayer graphene sheet suspended over multiple cavities and clamped by two metal contacts. Suspended graphene, as opposed to substrate-based graphene, significantly reduces the surface charge hindrances and allows for ultrasensitive detection of gas molecules. The fabricated graphene chip has been successfully tested for toluene vapors. Currently, testing is underway to functionalize graphene for selective detection of different gases.

References:

Yuan, Wenjing, and Gaoquan Shi. "Graphene-based gas sensors." Journal of Materials Chemistry A35 (2013): 10078-10091.

Kuila, Tapas, et al. "Recent advances in graphene-based biosensors." Biosensors and Bioelectronics12 (2011): 4637-4648.

Shao, Yuyan, et al. "Graphene based electrochemical sensors and biosensors: a review." Electroanalysis10 (2010): 1027-1036.

Jackowska, Krystyna, and Pawel Krysinski. "New trends in the electrochemical sensing of dopamine." Analytical and bioanalytical chemistry11 (2013): 3753-3771.
(Invited) A CPW-Fed Flexible Uwb Monopole Antenna for Iot Applications
Authors: Saha Tonmoy Kumar , Knaus Tyler N , Sekhar Praveen K.
Published: February 2020

In this paper, a coplanar waveguide (CPW)-fed circular ultra-wideband (UWB) antenna is reported. The antenna is designed, simulated, fabricated, and tested experimentally. The antenna operates over a 3.8-30 GHz (155% fractional bandwidth) range with a return loss of 10 dB or more and voltage standing wave ratio (VSWR) < 2. The designed monopole antenna is of dimensions 33.1 mm x 33.84 mm with an electrical size of 0.42 λ x 0.43 λ at 3.8 GHz frequency. The antenna is fabricated on Kodak 4-Star photo paper with a dielectric permittivity of 2.85, loss tangent of 0.05, and a thickness of 0.254 mm. Fujifilm Dimatix 2831 was used as the inkjet printer. The designed antenna exhibits nearly omnidirectional radiation patterns over the entire impedance bandwidth. Considering the miniature size, higher operating bandwidth, and flexible characteristics of the substrate the presented antenna can be used for Internet of Things (IoT) applications.
(Invited) Structural Analysis of Multifunctional Ionic Gels
Authors: Ahmed Kumkum , Naga Naofumi , Khosla Ajit , Kawakami Masaru , Furukawa Hidemitsu
Published: February 2020

Ionic liquied mediated gels commonly known as ion gels or ionic gels have received remarkable attention for their advanced application in electrochemical and electromechanical devices, such as actuators, lithium batteries, electric double-layer capacitors, dye-sensitized solar cells and fuel cells [1, 2]. Investigation of the internal structure of ionic gels have been previously reported by our research group to understand their network homogeneity in association with mechanical characterization[3]. In this work we focused to determine structural analysis of ionic gels combining multifunctional thiol monomers and IL 1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide (BMImFSI). Therefore, we developed thiol monomer-based ionic gels via thiol-ene click reaction with theoretically homogeneous uniform network and investigated their mechanical properties using both conventional destructive method i.e. compression test and a unique nondestructive method using mesh size by scanning microscopic light scattering (SMILS) techniques [4]. The mesh size of the IGs was found to be highly dependent on the functionality of the monomer both in IL and conventional solvent media. Also long chain crosslinkers have been found to form dangling chain within the network hindering their homogeneous network formation. Thus our systems can offer to combine internal structures with the mechanical properties for characterization of soft materials in smart nondestructive ways.

References

[1] N. V. Plechkova, K. R. Seddon, Chem. Soc. Rev, 37, 123-150 (2008).

[2] T. Welton, " Chem. Rev
,
99, 2071-2084 (1999).

[3] Ahmed, K., Watanabe, Y., Higashihara, T. Arafune, H. Kamijo, T., Morinaga, T. Sato, T., Makino, M. Kawakami, M., Furukawa, H. Microsyst Technol 22, 17 (2016).

[3] H. Furukawa, K. Horie, R. Nozaki, M. Okada, Phys. Rev. E, 68, 031406 (2003)
Ag-Decorated Multi-Wall Carbon Nanotubes for Acetone Gas Sensing
Authors: Young Sheng-Joue , Lin Zheng-Dong , Khosla Ajit
Published: February 2020

In this study, room-temperature Acetone gas platform with enhanced sensitivity, superfast response and recovery, and good stability, using Ag nanocrystal-functionalized multiwalled carbon nanotubes. High-density carbon nanotubes (CNTs) are grown on an oxidized Si substrate by thermal chemical vapor deposition (CVD). The average length and diameter of the CNTs were about ~4.52μm and ~45nm, respectively. Ag nanoparticles were coated onto nanotube surfaces to a thickness of approximately 5nm and the CNTs thus formed could be utilized to sense acetone vapor. Functionalized CNT gas sensors exhibited better performances compared to unmodified CNTs, making them highly promising candidates for environmental air monitoring applications.
Development of Multi-Material 3D Printer
Authors: Basher Samiul , Ahmed Kumkum , Saito Azusa , Khosla Ajit , Kawakami Masaru , Furukawa Hidemitsu
Published: February 2020

The aim of developing a multi-material 3D printer is to print an object with a different kind of soft and hard material in a single run. It is expected that the combination of printing soft and hard material will be a new kind of 3D printer. The main printing material for this printer is the conductive based soft filament made by our laboratory “Soft & Wet Matter Engineering Laboratory”, along with other different soft filament and hard plastic filament to create a fully functional, multi-material printer to print objects in a single printing run with greater diversity and lower cost than any other single material printer. The biggest challenge for making this printer is to develop a soft material’s extruder because in 3D printer most of the materials are used is hard filament. So, to overcome this we are developing a special type of screw-based Extruder, where a huge range of polymer material can be processed in an application of 3D printer objects. This type of extruder is not so common in 3D printing field. Instead of the filament, we will use the conductive material as pellet or powder for this screw-based extruder. It is assumed that this type of screw-based extruder can solve the problem of combination of printing soft and hard material in a single run. Such type of screw base extruder will be a new era of the 3D printer and it could be a good STEM tool in Sensor and Robotics. Moreover, it is expected that it will be a new addition to the additive manufacturing process.
Tunable Shape Memory Polymer with Adhesive Property at Body Temperature for Shape Conformable Wearable Sensor Skins
Authors: Shiblee MD Nahin Islam , Ahmed Kumkum , Nagahara Larry A. , Thundat Thomas , Furukawa Hidemitsu , Kawakami Masaru , Khosla Ajit
Published: February 2020

Previously our group has developed poly(dimethyl acrylamide-co-stearyl acrylate (DMAAm-co-SA) based shape memory gels (SMG) [1] with high mechanical strength, very good transparency and biocompatibility having potential application in different sectors [2]. Most commonly used polymers in order to fabricate sensor skins is Polydimethylsiloxane (PDMS), but has a major drawback that it is not adhesive in nature [3, 4, 5].

In order to over come this problem, in this work we have incorporated adhesive properties by copolymerizing lauryl acrylate along with DMAAm and SA. The developed gels at body temperature had high transparency, good adhesive properties and wearability. Composition and temperature dependent adhesive properties of DMAAM-co-SA-co-LA has been investigated along with their mechanical, swelling and thermal properties and best suited adhesive SMG has been utilized to develop wearable skin sensor.

References:

Kabir, M.H., Ahmed, K. Furukawa, H., Microelectron. Eng. 150, 43–46 (2016).

Amano, Y; Hidema, R; Gong, J; Furukawa, H. Chem Lett.,41, 1029-1031 (2012)

Khosla, A., and B. L. Gray. "New technologies for large-scale micropatterning of functional nanocomposite polymers." In Nanosensors, Biosensors, and Info-Tech Sensors and Systems 2012, vol. 8344, p. 83440W. International Society for Optics and Photonics, 2012. https://doi.org/10.1117/12.915178

Hesketh, Peter J., Durga Misra, Seiichi Takamatsu, Toshihiro Itoh, Ajit Khosla, Amir H. Saheb, Michelle Leon, and Mira Josowicz. "Conducting polymers and their applications." Electrochemical Society Interface 61 (2012): 3-4.

Khosla, A., and B. L. Gray. "Fabrication and properties of conductive micromoldable thermosetting polymer for electronic routing in highly flexible microfluidic systems." In Microfluidics, BioMEMS, and Medical Microsystems VIII, vol. 7593, p. 759314. International Society for Optics and Photonics, 2010. https://doi.org/10.1117/12.840911