Theoretical Study of Novel B2CO Compounds with High Hardness

Two B2CO phases (oP8’ with sp2-sp3 hybridization coexist and mP16 with unitary sp3 hybridization) were discovered via structure searching and stability analysis. The study of formation enthalpy reveals that high pressure (HP) technology performed maybe an important method for synthesis. Among all isoelectronic with diamond (IED) B-C-O phases, oP8’ has the smallest gap and mP16 has the widest gap. With pressure increasing, for B2CO phases with high symmetry and composed of sp3 hybridization, their band gaps all increases monotonically; for B2CO phases composed by sp3-sp2 hybridization coexist or with low symmetry like mP16, their band gaps increased first and then decreased. oP8’ and mP16 both have large mechanical modulus and they are typical materials with high hardness. Pressure has a positive correlation with its mechanical modulus.

Enhancing sensitivity of QCM for dengue type 1 virus detection using graphene-based polymer composites

Graphene oxide-molecularly imprinted polymer composites (GO-MIP) have attracted significant attention as recognition materials in sensing due to their outstanding properties in terms of electrical and thermal conductivity, high mechanical modulus, and the comparably straightforward way to functionalize them. The aim of this study was to design a MIP-based sensor recognition material and enhance its sensitivity by blending it with GO for sensing a harmful dengue hemorrhagic fever pathogen, namely the dengue type 1 virus (DENV-1). Polymer composites comprising GO incorporated to an acrylamide (AAM)/methacrylic acid (MAA)/methyl methacrylate (MMA)/N-vinylpyrrolidone (VP) copolymer were synthesized and compared to the “pure” MIP, i.e., the copolymer without GO. The pure polymer revealed a zeta potential of + 9.9 ± 0.5 mV, whereas GO sheets prepared have a zeta potential of − 60.3 ± 2.7 mV. This results in an overall zeta potential of − 11.2 ± 0.2 mV of the composite. Such polymer composites seem appropriate to bind the positively charged DENV-1 particle (+ 42.2 ± 2.8 mV). GO-MIP coated onto 10-MHz quartz crystal microbalance (QCM) sensors indeed revealed two times sensitivity compared to sensors based on the pure MIP. Furthermore, GO-polymer composites revealed imprinting factors of up to 21, compared to 3 of the pure MIP. When plotting the sensor characteristic in a semilogarithmic way, the composite sensor shows the linear response to DENV-1 in the concentration range from 100 to 103 pfu mL−1. The corresponding limits of detection (S/N = 3) and quantification (S/N = 10) are 0.58 and 1.94 pfu mL−1, respectively. Furthermore, imprinted polymer composites selectively bind DENV-1 without significant interference: DENV-2, DENV-3, DENV-4, respectively, yield 13–16% of DENV-1 signal. The sensor requires only about 15–20 min to obtain a result. Graphical abstract

Synergistic modification of the tribological properties of polytetrafluoroethylene with polyimide and boron nitride

Polytetrafluoroethylene (PTFE) blended with polyimide (PI) and filled with boron nitride (BN) is prepared through cold pressing and sintering for composites with remarkable wear resistance and reduced coefficient of friction (COF). The characterizations show that BN and PI at different levels, improve the hardness, dynamic thermo-mechanical modulus, thermal conductivity, and tribological properties of PTFE. PI boosts the dispersion and bonding of BN in PTFE. In dry sliding friction of a block-on-ring tribometer, the wear rate and COF of 10:10:80 BN/PI/PTFE reduce to almost 1/300 and 80% of those of pure PTFE, respectively, as the wear mechanism transition from being adhesive to partially abrasive. This occurs only when the additives BN and PI induce a synergistic effect, that is, at concentrations that are not higher than ca. 10 wt% and 15 wt%, respectively. The obvious agglomeration at high percentages of added PI and severe conditions (400 N and 400 rpm) induce strong adhesive failure. The variations in the tensile properties, hardness, crystallization, and microstructure of the composites correspond to different effects. The multiple parameters of the plots of wear and friction are transformed into their contour curves. The mechanism transition maps aid in understanding the influence of various test conditions and composite compositions on the contact surfaces in the space-time framework of wear.

Dynamic mechanical analysis in materials science: The Novice’s Tale

There are a few useful textbooks and online materials available on dynamic mechanical analysis (DMA) but no short and succinct article that will be useful for a beginner. Here we are providing a brief introductory overview of DMA, followed by details of the different types of measurements possible with a typical DMA instrument. Some of the important measures needing to be taken in these analyses are also summarized, along with the possibilities of designing new experiments with the help of a DMA instrument. Oscillatory stress/strain-assisted studies of two different types of membranes—a polymer membrane and a membrane which consists of assembled ultra-thin oxidized graphene flakes—are discussed at the end. These studies show the vast possibilities of DMA in understanding the different aspects of solids, such as their phase transitions, microstructure, damping, complex interactions in the composite matrix, and also about the mechanical modulus of the solid membrane. Hence this article discusses the new avenues for DMA in different fields and takes the reader from the fundamentals to its advanced applicability.

A Skin-Conformal, Stretchable, and Breathable Fiducial Marker Patch for Surgical Navigation Systems

Augmented reality (AR) surgical navigation systems have attracted considerable attention as they assist medical professionals in visualizing the location of ailments within the human body that are not readily seen with the naked eye. Taking medical imaging with a parallel C-shaped arm (C-arm) as an example, surgical sites are typically targeted using an optical tracking device and a fiducial marker in real-time. These markers then guide operators who are using a multifunctional endoscope apparatus by signaling the direction or distance needed to reach the affected parts of the body. In this way, fiducial markers are used to accurately protect the vessels and nerves exposed during the surgical process. Although these systems have already shown potential for precision implantation, delamination of the fiducial marker, which is a critical component of the system, from human skin remains a challenge due to a mechanical mismatch between the marker and skin, causing registration problems that lead to poor position alignments and surgical degradation. To overcome this challenge, the mechanical modulus and stiffness of the marker patch should be lowered to approximately 150 kPa, which is comparable to that of the epidermis, while improving functionality. Herein, we present a skin-conformal, stretchable yet breathable fiducial marker for the application in AR-based surgical navigation systems. By adopting pore patterns, we were able to create a fiducial marker with a skin-like low modulus and breathability. When attached to the skin, the fiducial marker was easily identified using optical recognition equipment and showed skin-conformal adhesion when stretched and shrunk repeatedly. As such, we believe the marker would be a good fiducial marker candidate for patients under surgical navigation systems.

Relationships between wood properties of small clear specimens and structural-sized boards in three softwood species

Research on the mechanical and physical properties of wood is commonly carried out on either small clear specimens or structural-sized boards. The first approach was more frequently utilized in the past, while the latter is more commonly used nowadays. However, there is very little information on how the two approaches relate with one another. This study aimed to quantify the relationships between the mechanical [modulus of elasticity (MOE) and bending strength] and physical properties (density) of both specimen sizes. A total of 1376 structural-sized boards from three different species (Douglas-fir, Norway spruce and Sitka spruce) were tested in bending, after which a small clear specimen was extracted from the undamaged portion of each board and re-tested in bending. Prior to destructive testing, all boards and clear specimens were evaluated using non-destructive technology. Poor-to-moderate relationships were found between all measured mechanical and physical properties of structural-sized timber and small clear specimens. In both specimen sizes, the properties correlated with one another within the same specimen size, as well as across the two sizes. The strength of correlations appears to be somewhat species dependent. Relatively good relationships were identified when comparing the mean tree values of the properties examined, suggesting either method can be used for a tree-level comparison. The non-destructive evaluation of specimens was shown to reflect the measured properties moderately well, with the relationships changing significantly depending on which measured property was being predicted.