Mechanical Properties of Electrospun, Blended Fibrinogen: PCL Nanofibers

Electrospun nanofibers manufactured from biocompatible materials are used in numerous bioengineering applications, such as tissue engineering, creating organoids or dressings, and drug delivery. In many of these applications, the morphological and mechanical properties of the single fiber affect their function. We used a combined atomic force microscope (AFM)/optical microscope technique to determine the mechanical properties of nanofibers that were electrospun from a 50:50 fibrinogen:PCL (poly-ε-caprolactone) blend. Both of these materials are widely available and biocompatible. Fibers were spun onto a striated substrate with 6 μm wide grooves, anchored with epoxy on the ridges and pulled with the AFM probe. The fibers showed significant strain softening, as the modulus decreased from an initial value of 1700 MPa (5–10% strain) to 110 MPa (>40% strain). Despite this extreme strain softening, these fibers were very extensible, with a breaking strain of 100%. The fibers exhibited high energy loss (up to 70%) and strains larger than 5% permanently deformed the fibers. These fibers displayed the stress–strain curves of a ductile material. We provide a comparison of the mechanical properties of these blended fibers with other electrospun and natural nanofibers. This work expands a growing library of mechanically characterized, electrospun materials for biomedical applications.

Temperature Controlled Synthesis of Ce–MnO2 Nanostructure: Promising Electrode Material for Supercapacitor Applications

The objective of this study was to prepare Ce–MnO2 nanostructure composite as an electrode material for supercapacitor application. Ce–MnO2 nanostructure composite was synthesized by facile hydrothermal method at different temperatures. Structural details of pure and Ce–MnO2 nanostructure composite were studied using powder X-ray diffraction technique. The formation of flower like structure and strong interaction with Ce and MnO2 were confirmed by field emission electron microscope technique. Their electrochemical performances were elucidated by using cyclic voltammetry, charge–discharge, and electrochemical impedance spectroscopy techniques. Nearly rectangular shaped cyclic voltagram was observed for synthesized Ce–MnO2 nanostructure composite electrode, indicating the existence of electric double layer capacitance nature. Ce–MnO2 (130) nanostructure composite exhibited high specific capacitance value of 147.25 F/g at applied current density of 1 A/g in 1 M Li2SO4 aqueous electrolyte. Furthermore, resistive and capacitive behaviors of these electrodes were studied from Nyquist and bode diagrams within frequency range of 10 mHz to 100 kHz.

Influence of microcork particles on the lap shear strength of an epoxy adhesive subjected to fatigue loading and different environmental conditions

The present study deals with the effects of temperature and cyclic loading on the strength of single lap adhesive joints enhanced with different amounts of microcork particles. To achieve this, different joints with various overlap lengths were manufactured and tested. The joints were tested at two different temperatures (−20 ℃ and 75 ℃) in quasi-static conditions. Results of high temperature (75 ℃) show that the joints tensile strength decreases with the amount of cork particles. For low temperature (−20 ℃), the strength of the joint with 1 vol.% of cork increased; however, higher amounts of cork led to a reduction of the joint strength. To investigate the influence of cork particles on the fatigue endurance, joints were tested at room temperature under sinusoidal cyclic loading. Based on the experimental data it was found that the cork particles can significantly improve the fatigue life of adhesive joints (up to 4.6 times). Microfailure analysis of the tested joints was also performed using the scanning electron microscope technique.

Novel X-ray Microscopic Chemical Imaging for Rapid Non-Destructive Identification of Structural and Compositional Defects from Microbumps to FinFET

New heterogeneous 3D integration schemes and continuing miniaturization of semiconductor packaging components, such as micropillars, are driving demand for substantive changes to conventional PFA (physical failure analysis). In particular, desired performance capabilities include the ability to nondestructively determine failures within seconds to minutes. New tools should be quantitative, have sufficient resolution to determine sub-micron sized defects and voids in TSVs at the wafer or package level. It should also measure thickness and their material composition of multilayer structures above the wafer surface, such as microbumps, or those below the surface including UBM and RDL. In this paper we are introducing a novel x-ray fluorescence microscope technique capable of solving the above applications in advanced packaging for PFA and process development. The same technique can also be applied in the front end metrology of new gate materials, 3D FinFET structures within test structures in patterned wafers. Characterization of sub nanoscopic changes (sensitivity of sub-angstrom) in film and dopants deposited in 3D structures will also be shown. With its high sensitivity for trace materials, contamination analysis of post hard mask residue, post metal etch residue especially in high aspect ratio structures is also possible.

Characteristic and Preparation of TiO2/PVP Nanofiber Using Electrospinning Technique

In this work, titanium dioxide (TiO2) ceramic nanofiber was prepared by homemade electrospinning technique. A homogeneous solution of titanium isopropoxide in polyvinyl pyrrolidone (PVP) was prepared. The thermal behavior of the fiber was characterized by differential thermal analyzer (DTA) and thermogravimetric analysis (TGA) to obtain the calcination temperature range. Fourier transform infrared spectroscopy (FTIR) was employed to analyze the chemical structures of the TiO2/PVP composite nanofibers. The structural phase formations were characterized by x-ray diffraction technique (XRD). It has been found that the single phase of anatase and rutile were obtained at the calcinations temperature at 500 and 900 °C, respectively. The microstructure was characterized by a scanning electron microscope technique (SEM). The diameter of titanium oxide nanofibers were in the range of 70 nm to 300 nm and decrease as the calcination temperature increasing. The results indicated the effect of calcination temperature on the crystalline phase and morphology of the nanofiber.

Some of the physical and mechanical properties of composites made from Tetra Pak™/LDPE

This study investigated the effect of milk packet waste (Tetra Pak™) and maleic anhydride–grafted polyethylene (MAPE) on the physical and mechanical properties of wood–plastic composites. Tetra Pak was used in four levels (0, 10, 20, and 30%) and MAPE was applied in two levels (0 and 3%). The morphology of the samples was characterized using the scanning electron microscope technique. The results showed that adding Tetra Pak and MAPE to samples increased the flexural strength and modulus of elasticity and reduced 24-h water absorption and thickness swelling. The results were also confirmed by electron microscopy images.

A Low Cost Time-Coded Confocal Microscope

Confocal microscopy is a high resolution microscope technique, which operates by scanning a diffraction limited focal spot over a sample. This focal point on the sample is then imaged through an objective lens and a pinhole to ensure that only the information coming from the focal plane is captured and the information from the other planes are blocked by the pinhole. Although this gives better lateral resolution, this method is inefficient in terms of the amount of light required and the scanning time. In this paper, we discuss an alternative solution using digital micromirror device (DMD) to perform multiple focal points scanning simultaneously. This is done by projecting a series of orthogonal codes onto the DMD. The corresponding images obtained from the orthogonal codes are then saved and processed offline in a computer to calculate a confocal image. We use incoherent illumination rather than a laser source as used previously. We also discuss a key issue in this confocal system, which is a suitable separation between each focal spots and a crosstalk between them. We demonstrate that the proposed confocal configuration with the DMD device improves the light efficiency, the scanning time through the parallel confocal spots and a laser source is not required.