Volume 9, Issue 11, November 2018

Multilayer ceramics as integration platform for sensors in in-vitro cell culture reactors

Heike Bartsch; Martin Baca; Uta Fernekorn; Marcel Himmerlich; Jens Müller; Andreas Schober Hartmut Witte

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 748-752
DOI: 10.5185/amlett.2018.2090

Monitoring systems that are capable to record neuronal activity in in-vitro cell cultures are prerequisite to the comprehensive investigation of neuronal processes. Low temperature cofired ceramics are a suitable platform for rapid prototyping of biological reactors, entailing a wide assortment of integration-capable sensors. Neuronal spikes capture is fundamental for understanding of the signal propagation within the neuronal network. It requires reliable electrodes, which can be arranged 3-dimensionally in an in vitro cell culture. Thick film gold electrodes have been proven for such applications, however their characteristics especially at small dimensions stray strongly. This work investigates thin films separating small thick film gold electrodes and an electrolyte solution with regard to their influence on the charge transport processes in such systems. PEDOT:PSS layer and TiOxNy deposited on LTCC gold electrodes, including their impedance characteristics are discussed and compared. TiOxNy layers with serial resistance Rs of 32 kΩ and serial capacitance Cs of 4.1 pF measured at 1 kHz are proposed to be the used as sensing elements in 3-dimensional in vitro cell cultures.                                                                       

Behavior of EB FRP masonry bond under service temperature

Zuhair Al-Jaberi; John J. Myers; K. Chandrashekhara

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 753-759
DOI: 10.5185/amlett.2018.2152

The interest in advanced composites in repairing and strengthening infrastructure systems has considerably increased, especially as the application externally bonded (EB) fiber reinforced polymer (FRP) has become more well established. Previous research on bond behavior has focused on impact of durability by considering exposure to harsh environmental conditions and testing the specimens after exposure, rather than testing bond performance during exposure. The influence of directly applying temperature on bond behavior represents an open topic that needs to be investigated in more detail. This study is one of the first studies to investigate the bond behavior when the composite is subjected to tension force simultaneously with applying temperature. The temperatures considered in this study were at freezing, ambient, and high temperature, which are more representative of structural elements under field conditions. A total of 16 specimens were strengthened and tested under single-lap direct shear. The key parameters investigated include (a) the type of fiber [laminate carbon vs. wet layup glass] (b) the level of temperature applied on specimen, including ambient condition 21°C (70 °F), freeze condition -18 °C (0 °F) and hot weather 49 °C (120 °F), and (c) the exposure regime (direct exposure during loading process vs. loading after exposure). Most of the specimens were subjected to tension force simultaneously with applying temperature, and the other specimens were later tested after exposure to the heating and cooling cycles. These cycles are proposed to simulate 20 years of the typical in-situ weather conditions in the Central United States. The results showed that overall the EB strengthening systems exhibited good performance when subjected to cycles of heating and cooling prior to testing. High reduction of FRP-epoxy bond properties was up to 59% when exposed to high service temperatures. Different modes of failure were observed such as debonding at fiber-matrix interface and debonding due to shearing in laminate.

Magnetism of ACFs and superfluidity of 4He adsorbed in ACFs

Yoshiyuki Shibayama

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 760-766
DOI: 10.5185/amlett.2018.2129

Activated carbon fibers (ACFs) are a nanoporous form of carbon with huge specific surface areas caused by a three-dimensional random network of nanographites. Because of nano-size effects, non-bonding π-electron spins emerge on the nanographite. The nanographite random network produces many nanopores with a mean size of several nanometers and creates a host system for various guest molecules in ACFs. In order to investigate the magnetic properties of nanographite and the superfluidity of 4He restricted in nano-spaces, the magnetization of ACFs and superfluidity of 4He adsorbed in ACFs have been investigated. The magnetization shows an antiferromagnetic interaction between the non-bonding π-electron spins. Near the insulator-metal transition caused by heat treatment of ACFs, spin glass-like disordered magnetism observed. Up to an 4 He coverage of 22.6 μmol/m 2 , no superfluidity is observed due to the strong van der Waals force between 4 He and nanographite. Over 23.7 μmol/m 2 4He coverage, the superfluid transition is observed at approximately Tc ~ 500 mK. Upon increasing the 4 He coverage, the superfluid density increases, but no change in Tc is observed. These observations indicate that the thickness of superfluid films on nanographite is restricted by the slit type pore shape of ACFs. Copyright © 2018 VBRI Press.

Joule heating of logs for phytosanitary purposes and timber processing pre-treatment

William J.B. Heffernan; Nurzhan Nursultanov; Ryan van Herel; Thomas Smart

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 767-775
DOI: 10.5185/amlett.2018.2133

Joule heating has recently been investigated as a potential alternative to chemical fumigation for phytosanitary treatment of Pinus radiata logs exported from New Zealand. The research was driven by concern regarding the effects of methyl bromide release to atmosphere, following fumigation, as highlighted by the Montreal Protocol. The work has involved creating 1 dimensional and 3 dimensional computer models of the Joule heating process in P. radiata, building a laboratory-scale log test rig with suitable instrumentation and control systems, heating approximately 60 P. radiata logs and using the measured data to refine and validate the models. While engaged in this work it became clear that the process could also potentially be applied to heat veneer peeler logs. This paper describes the application of the 1 dimensional model and laboratory-scale test rig to a typical P. radiata export log and to a Eucalyptus nitens log prepared for veneer peeling. The results demonstrate that, despite the heterogeneities of the timber, the technique is capable of achieving the required temperature profiles for both applications and that the model is a sufficiently good representation of the process to provide a viable control method. 

Design of FES based muscle stimulator device using EMG and insole force resistive sensors for foot drop patients

Muhammad A. Khan; Saad Abdullah; Mauro Serpelloni; Emilio Sardini

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 776-780
DOI: 10.5185/amlett.2018.2170

In the presented research, design of functional electrical stimulation (FES) based muscle stimulator device has been described which is used to correct and enhance the gait activity of foot drop patients. The device mainly comprises of FES unit for electrical pulse generation, an electromyography (EMG) sensor V3 for feedback system and insole force-sensitive resistive sensors (FSR) to control ON/OFF timing of device. The device controls the ankle flexion without excessive eversion or inversion of foot (i.e. balanced flexion) by stimulation of common peroneal nerve and tibialis anterior muscle (TA). The efficiency of device is assessed by evaluating gait temporal and spatial parameters (TSP’s) and 3-dimensional gait kinematics (ankle flexion) of footdrop patients by “Peak Motus Motion Measurement System”. It has been found that use of FES stimulator increases the walking speed by 19%, cadence by 7%, step length by 11% and stride length by 15.5%. In addition, it is also observed that stride time, stance time, step time, single support time and double support time is decreased by 5%, 17%, 22%, 15% and 18% respectively. Moreover, kinematics analysis of foot shows that the device prevented the footdrop up to 30° by controlling the ankle flexion and extension magnitude. Thus, the obtained results suggest that the proposed FES based stimulator device provides enough stimulation to peroneal nerve required for stable gait activity of footdrop patients. Copyright © 2018 VBRI Press.

Structure and properties degradation of the nuclear graphite under neutron irradiation

Boris A. Gurovich; Denis A. Kuleshov; Dmitriy A. Maltsev; Oleg K. Chugunov; Alexey S. Frolov; Yaroslav I. Shtrombakh

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 781-788
DOI: 10.5185/amlett.2018.2132

The operation of nuclear graphite in graphite-moderated reactors is accompanied by its properties degradation under the influence of neutron irradiation, which limits their service life. In this connection, it is of interest to identify the mechanisms that determine the properties degradation of graphite materials at various operational stages of operating RBMK power reactors.

Structural performance of severely damaged reinforced concrete beams after SRP repair

Hayder H. Alghazali; Zuhair K. Al-Jaberi; Zena R. Aljazaeri; John J. Myers

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 789-795
DOI: 10.5185/amlett.2018.2153

To experimentally examine the ability of the steel reinforced polymer (SRP) in restoring the moment capacity compromised by damage in the main steel reinforcement, six full-scale reinforced concrete (RC) beams were designed to simulate impact damage from over height vehicle collision. The simulation was represented by concrete beams reinforced with discontinuous reinforcement (splice in maximum moment region) and tested until failure due to splice. The damaged concrete was repaired, and the SRP system (longitudinal soffit laminates and transverse U-wraps) was applied to restore the original moment capacity. All beams were 10 ft (3.0 m) in length, 18 in. (457 mm) in depth, and 12 in. (305 mm) in width. Different repairing configurations were investigated. The studied variables were the provided laminate area and the amount and distribution of U-wraps. The ultimate load capacity, deflection, and mode of failure were recorded during testing. The test results were compared to beam results with continuous reinforcement. It was concluded that the repairing beams with the SRP system can restore the damaged beams to a capacity similar to that of a non-damaged reinforced concrete (RC) beam with continuous reinforcement.

Polycaprolactone/organoclay biodegradable nanocomposites: dissimilar tendencies of different clay modifiers

Romina P. Ollier; Matias R. Lanfranconi; Vera A. Alvarez; Leandro N. Ludue

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 796-804
DOI: 10.5185/amlett.2018.1828

In this work, biodegradable nanocomposites based on polycaprolactone (PCL) reinforced with 2.5, 5.0 and 7.5 wt.% of two different clays, a commercial organo-clay (Cloisite 20A, C20A) and a laboratory modified bentonite with tributylhexadecyl phosphonium bromide (bTBHP), were prepared by melt intercalation followed by compression molding. The study contemplates the analysis of chemical (Infrared Spectrometry, FTIR), morphological (X-Ray Diffractometry, XRD, Scanning Electron Microscopy, SEM, and Transmission Electron Microscopy, TEM), rheological, thermal (Differential Scanning Calorimetry, DSC, and Thermogravimetrical Analysis, TGA) and mechanical properties (tensile tests), which are important properties for packaging applications.In previous works, we concluded that higher clay dispersion degree inside the PCL matrix is expected when clays with large interlayer distance, strong hydrophobicity and strong processing stability are used. In the present work, the opposite result was obtained. Although the phosphonium treated clay (bTBHP) showed the largest interlayer distance (d001), strongest hydrophobicity and the best processing stability, the clay dispersion degree inside PCL was worse than in the case of the alkylammonium treated clay (C20A). PCL/bTBHP nanocomposites showed weaker mechanical properties in comparison with PCL/C20A ones, which is in accordance with the morphological analysis. On the other hand, the thermal properties of the matrix were not substantially affected by clay incorporation in both nanocomposites. 

Synthesis and characterization of pure BiFeO3 using various complexing agents by Sol-gel method

Balesh Kumar Vashisth; Jarnail S. Bangruwa; S. P. Gairola; Vivek Verma

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 805-810
DOI: 10.5185/amlett.2018.2173

Pure BiFeO3 (BFO) nanoparticles were prepared using various complexing agents like citric acid, malonic acid, succinic anhydride and tartaric acid by sol-gel method annealed at different temperatures (400 °C, 500 °C, 600 °C). X-Ray diffraction pattern of various samples show the degree of formation of required phase. Particle size of pure phase BFO has been shown using TEM image. Scanning Electron Microscopy studies for different samples give detailed study of morphology of samples. Ferroelectric and magnetic studies of best prepared samples show their comparative multiferroic properties. Dielectric analysis also shows the variation in dielectric loss, real and imaginary part of permittivity versus frequency at room temperature.

Effect of sulfurization temperature on optical and compositional properties of sputtered Zn(O, S) thin films

K. S. Gour; A. K. Yadav; Rahul Kumar; J. S. Tawale; V. N. Singh

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 811-815
DOI: 10.5185/amlett.2018.2125

Zinc oxysulfide or Zn(O,S) is emerging as an alternate n-type buffer layer for kesterite, chalcogenides and CdTe based thin film solar cell due to it is being made from non-toxic elements and tunable bandgap, its suitable optical and electrical properties required for a buffer layer. Generally, buffer layers of these solar cells are deposited using chemical bath deposition (CBD) techniques, but these require breaking of vacuum and again inserting the sample in vacuum during solar cell fabrication, which is not economical and is cumbersome. Sputtering is considered to be industrial process and therefore, here we have deposited Zn(O,S) thin film by sputtering technique and effect of sulfurization temperature on bandgap and composition of Zn(O,S) films have been studied. The bandgap of deposited films changed from 3.36 eV to 3.15 eV by changing the sulfurization temperatures. By changing the sulfurization temperature, the composition of films also changed. Crystallite size (D) of Zn(O,S) films increased from 12.1 nm to 22.3 nm by varying the sulfur content for samples S1-S4, respectively. Optical, morphological, compositional and structural properties have been studied using UV-Vis-NIR spectroscopy, Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS) and X-ray diffractometer (XRD), respectively. 

Staking lay-up effect on dynamic compression behaviour of e-glass/epoxy composite materials: experimental and numerical investigation

Mostapha Tarfaoui; Mourad Nachtane

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 816-822
DOI: 10.5185/amlett.2018.2060

Several industrial applications have exposed polymer matrix composite materials to a very high strain rate loading conditions, requiring an ability to understand and predict the material behaviour under these extreme conditions. Many composite aircraft structures such as fuselage, wing skins, engine nacelles and fan blades are situated such that impacts at high strain rates are a realistic threat. To investigate this threat, high velocity impact experiments and subsequent numerical analysis were performed in order to study the compressive loading of composite materials at high strain rates. Specimens are subjected with various orientations from low to high strain rates to determine the compressive material properties. Three fibre orientations such as: ±20°, ±60° and 90° of cubic geometry are tested in in-plane direction. The tests show a strong material sensitivity to dynamic loading and fibre direction. In the second part, the FEA results of the dynamic tests resulting in no damage appeared satisfactory. The FEA gives results which are in coherence with the experimental data. The improved understanding of these phenomena and the development of predictive tools is part of an ongoing effort to improve the long-term integrity of composite structures under dynamic loads.

Facile Electrostatic Immobilization of Glucose Oxidase onto Citrate Capped Gold Nanoparticles for Surface-enhanced (Bio)-Catalysis

Ayushi Tiwari; Anshuman Mishra

Advanced Materials Letters, 2018, Volume 9, Issue 11, Pages 823-830
DOI: 10.5185/amlett.2018.2007

Diabetes mellitus is a serious life-time health issue which has been increasing among the greater population, approximately 285 million people carrying this disease worldwide. In this study, we have functionalised the gold nanoparticles (AuNPs) with biocatalytic enabled optical property, it is the subject of the study for detecting glucose towards the development of photometric nano-transducer. The citrate capped AuNPs were used to warrant the electrostatic self-assembly of glucose oxidase (GOx) in the colloidal state. Glucose biocatalysis was studied through the nano-optical function of glucose on the surface of AuNPs. Using surface plasmonic resonance as analytical technique, we have determined the molecular binding interaction between glucose molecule and AuNPs surface. Based on the visible spectrum, successful immobilization of GOx onto AuNPs was demonstrated. The GOx functionalized AuNP exhibits catalytic activities for the oxidation of glucose and resulting change in the absorption peak of colloidal bio-assembly. It was observed that the absorbance at 520 nm was proportional to the concentration of glucose in the test samples. The Lambert-Beer law expresses the linear relationship between the absorbance and glucose concentration at a fixed wavelength, i.e., λmax at 520 nm. The precise detection of glucose is essential to monitor the biological level of glucose in the body. It can be concluded that the nano-(bio) gold surface exhibits a rapid photometric response with changes of glucose concentration in the test samples.