Search

In this study, we propose a way for miniaturization of mid-infrared (MIR) fibre bundles while maintaining low crosstalk and transmission losses. Such miniaturization of fibres is important when applying MIR in thin polycrystalline AgCl0.25Br0.75 fibres with a diameter of 110 µm, made using custom-designed extrusion components. These fibres were then mechanically assembled in an optical bundle of seven hexagonally arranged fibres. Transmission of MIR from a heat source through this bundle was compared with similar bundle of seven fibres with a diameter of 300 µm. It was found that both bundles are transparent to MIR in the spectral range of 2–20 µm corresponding to temperature range from –130 to + 1150 °C. They also have low crosstalks (

The positive temperature co-efficient (PTC) of resistivity in BaTiO3 is a grain boundary effect, where the resistivity increases by several orders of magnitude near the transition temperature from ...

Calcium carbonate and carbonate-hydroxyapatite are known to form inorganic components of crystals and calcareous concretions found in many non-skeletal tissues and structures including the pineal gland. We used advanced surface analyses techniques such as polarization microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), microfocus X-ray diffraction (XRD), transmission electron microscopy with selected area electron diffraction (TEM-SAED) to investigate samples extracted from rat pineal gland after irradiation with visible light for 12 h. Single-crystal X-ray diffraction showed that the concretions were largely amorphous with the presence of some nanocrystalline phases. High resolution TEM-SAED revealed the presence of iron oxide in the form of hematite. Spectroscopy data especially Raman spectroscopy revealed a mixed nature of these concretions, which corresponded reasonably with XPS, TEM and XRD. Overall the study confirms the presence of a mixed phase of calcium carbonates including calcite, aragonite and vaterite. We note that aragonite is not a common occurrence in vertebrates and recommend further investigation to rule out any link to pathology.

Arrays of micron-sized domains of modified surface potential were created on hydroxyapatite films by mid-energy (20 keV) electron beam irradiation available in a laboratory scanning electron microscope. The dosage of electron beam was varied between 10−3 and 103 μC/cm2 to inject charge into the film surface. Contrary to the conventional electrowetting theory, the dosage of injected charge used in creating such microdomains caused a gradual increase of the water contact angle from 57° to 93° due to the elimination of the polar component of the surface free energy. Surface contamination by carbonaceous species can be held only partially responsible for such behavior at lower dosage of electron beam. A transfer of free surface charge to water and an electron beam induced disruption of polar orientation of OH ions have been attributed to be influencial factors in the overall dewetting behavior.

This work investigates the converse piezoelectric effect in crystals of the protein lysozyme using Piezoresponse Force Microscopy (PFM) in contact and Hybrid modes. The mechanical properties of lysozyme crystals were mapped at the surface by means of Hybrid mode. In addition, ferroelectric loops were measured by the switching-spectroscopy PFM method (SS-PFM). We explore these findings using crystallographic principles and propose that the presence of defects within the crystal may lower the symmetry of lysozyme to a polar one. Our findings point towards the potential of exploiting lysozyme and other proteins in technical applications, especially those in which biocompatibility is critical. © 2018 Taylor & Francis Group, LLC.

This article pays tribute to the contributions of Professor Sidney B. Lang in the field of pyroelectricity of materials of biological relevance since his discovery in 1966 of pyroelectricity in bone and tendon. The article sets the perspective to understand the significance of this discovery and summarizes key progresses made in the field since then. It also provides an outlook for the direction in which future research in this field may take place.

It is widely recognized that hot working, grain structure, degree of deformation and crystal orientation can have a significant effect on the thermomechanical properties of Nitinol, the shape memory alloy of nickel and titanium, widely used in the biomedical device industry. In the current work, a novel hot-working process was applied to Nitinol rods with subsequent material hardness testing, electron backscatter diffraction (EBSD) and differential scanning calorimetry (DSC) analysis performed to determine the mechanical properties, grain texture and transformation temperatures of the processed Nitinol. The properties of the processed alloy, as ascertained by the aforementioned techniques, were compared to the as-received material. It was established that processing the material had the beneficial effect of softening the material from the as-received condition, making the material suitable for subsequent forming operations, such as cold drawing. EBSD results showed a strong preference towards a 〈1 0 1〉 texture in the processed material with some preference also towards a 〈1 1 1〉 texture. The results of the DSC analysis, which measured the transformation temperatures of the processed Nitinol material, showed a significant reduction in the austenite finish transformation temperature of the processed material compared to that of the as-received material. Tensile tests carried out to determine changes in the superelastic behaviour of the material due to the dieless drawing process corroborated and emphasized the results of the hardness tests, EBSD and DSC analyses. The process has resulted in a material with lower transformation temperatures, higher ductility and reduced tensile flow stress. The upper loading plateau begins at a lower strain and is present over a longer strain range.

Electrical properties of hydroxyapatite (HA) in the form of screen printed thick films that can be used as a biocompatible coating for bone and dental implants are reported. In particular, piezo- and pyroelectric behaviour of these films suggest that they can be used to promote faster healing of bones and prevent rejection of implants. Moreover, the reversible pressure-induced changes in their electrical characteristics can be employed for real-time in vivo pressure sensors implantable simultaneously, for example, with knee or hip prosthesis. The additional advantage of HA in the form of screen-printed thick films is that, due to the technology’s versatility, it can be produced on flexible substrate in any shape and size to suit the needs of various patients.

Here, we present experimental evidence of the direct piezoelectric effect in the globular protein, lysozyme. Piezoelectric materials are employed in many actuating and sensing applications because they can convert mechanical energy into electrical energy and vice versa. Although originally studied in inorganic materials, several biological materials including amino acids and bone, also exhibit piezoelectricity. The exact mechanisms supporting biological piezoelectricity are not known, nor is it known whether biological piezoelectricity conforms strictly to the criteria of classical piezoelectricity. The observation of piezoelectricity in protein crystals presented here links biological piezoelectricity with the classical theory of piezoelectricity. We quantify the direct piezoelectric effect in monoclinic and tetragonal aggregate films of lysozyme using conventional techniques based on the Berlincourt Method. The largest piezoelectric effect measured in a crystalline aggregate film of lysozyme was approxi...

A high X-ray visibility of surgical devices is critical during minimally invasive surgery for exact placement of these devices within the targeted anatomical site while keeping the X-ray exposure of the patient to a minimum. NiTi and common metallic biomaterials (e.g. stainless steel and Co-Cr alloys) used in minimally invasive surgery are inherently less visible due to their weak X-ray absorption ability (radiopacity). Dense and high atomic number elements such as platinum (Pt) have been added to NiTi and stainless steel to enhance radiopacity. Contrary to the conventional understanding of using heavier atoms, radiopacity enhancement can be achieved by adding rare earth (RE) lanthanide elements such as erbium (Er). The retention of the shape memory effect (SME) and superelasticity (SE) in NiTi-RE to a functional level is an important challenge. Here we take NiTi-Er as a case study and show that this alloy can be conveniently prepared by spark plasma sintering (SPS) and subsequently processed by conventional hot and cold working to a number of forms suitable for both biomedical and nonbiomedical applications. Higher visibility of these devices will provide ease of placement and manipulation of these devices, reduce patients’ trauma during deployment and will significantly reduce radiation dose received by a patient in his lifetime.

Nanotechnology is becoming important for the textile industry because of the unique technical and economic advantages that nanomaterials offer. Traditional methods used to impart different characteristics and functionality to textiles often do not lead to the desired results in an efficient way. Fabrics lose their properties during wearing, washing, dry cleaning and hot pressing. Nanotechnology may overcome these limitations of conventional methods and provide durability of textile functions. Nanoparticles that are applied on to the fabric have both a large surface area-to-volume ratio and high surface energy. Furthermore, nanoparticles that are attached to the fabrics may not significantly affect physical and mechanical properties such as breathability, hand feel, strength, wetting etc. Commercially available antimicrobial finishes are resistant to body fluids and processes of sterilization or disinfection. This last property is particularly important in developing MRSA-resistant textiles. We review works on textiles that offer resistance to MRSA and discuss how antibacterial nanoparticles can provide significant benefits when used in textiles for MRSA resistance in comparison to conventional textiles.

Various methods of the electrical modification of biomaterials are discussed in this Chapter, along with their advantages and disadvantages. Electrical modifications to impart electrical charge in biomaterials have been reported to have beneficial effect, in particular in osteogenesis. Higher rates of calcifications and cellular activities have been reported on negatively polarized Biomaterials' surfaces. This general observation cannot be reconciled purely due to the hydrophobicity/hydrophilicity of the surface, as the current theory does not suggest any influence of polarity of the surface on wetting behaviour. More fundamental studies are required to obtain a proper understanding of electrical modification on the reported selectivity in the stimulation of mineralization.

The most commonly used charge measurement methods in dry and wet condition are discussed in this Chapter. A number of methods [thermally stimulated depolarization current (TSDC), induction probe, field mill, electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KPFM)] for electrostatic charge measurement in dry conditions have been reviewed. The TSDC method is capable of measuring the integral charge at the surface, as well as in the volume of the sample, but the charge is destroyed by the measurement. On the other hand, induction techniques are sensitive only to the surface charge, but they are usually non-contact and non-destructive. In particular, scanning probe microscopy (SPM) techniques allow the measurement of surface charge with high lateral (tens of nanometres) and potential (∼mV) resolution. In wet conditions, the streaming potential technique is most commonly used for surface potential measurements, although KPFM can also be employed in certain cases.

This papers reports on the electrical properties of Hydroxyapatite (HA) in the form of screen-printed thick films with novel paste composition In particular, it is revealed for the first time that both high temperature treatment alone and a combination of high temperature and high voltage, i.e. poling, can cause comparable surface modifications resulting in pyroelectric behavior being recorded off HA thick film surface. Moreover, a reversible pressure-induced changes in the values of capacitance recorded in real time confirmed the piezoelectric behavior of HA thick films. Hydroxyapatite is biocompatible material, whose electrical characteristics can be employed in implantable devices for real-time in vivo pressure sensors applications such as in knee or hip prosthesis. In particular, piezo- and pyroelectric behaviour of these films suggest that they can have potential biosensor applications. The investigation of the electric properties of HA thick films is vital for the understanding of their bioactive characteristics for effective application in medical industry.

A quartz crystal microbalance (QCM) measures mass per unit area by determining the change in frequency of a quartz crystal resonator caused by the addition of a small mass. The nominal resonance frequency of the shear mode of the quartz sensor is 5 MHz. A frequency change of 0.1 Hz corresponds to an addition of about 2 ng/cm2 of mass to the quartz surface. Sauerbrey was the first to recognize the potential usefulness of the QCM technology and demonstrate its extreme sensitivity to mass changes [1]. He developed the fundamental equation describing the QCM: equation Here Δƒ = change in frequency (Hz), ƒ 0 = fundamental frequency of resonator (MHz), ρ q = quartz density (2.648 g cm−3), μ q = shear modulus of AT-cut quartz (2.947 × 1011 g cm−1 s−2), and Δm = mass change/unit area (µg/cm2). The AT-cut is used because its resonant frequency is almost temperature-independent.