Tribology—the study of contacting, sliding surfaces—seeks to explain the fundamental mechanisms underlying friction, adhesion, lubrication, and wear, and to apply this knowledge to technologies ranging from transportation and manufacturing to biomedicine and energy. Investigating the contact and sliding of materials is complicated by the fact that the interface is buried from view, inaccessible to conventional experimental tools. In situ investigations are thus critical in visualizing and identifying the underlying physical processes. This article presents key recent advances in the understanding of tribological phenomena made possible by in situ experiments at the nanoscale. Specifically, progress in three key areas is highlighted: (1) direct observation of physical processes in the sliding contact; (2) quantitative analysis of the synergistic action of sliding and chemical reactions (known as tribochemistry) that drives material removal; and (3) understanding the surface and subsurface deformations occurring during sliding of metals. The article also outlines emerging areas where in situ nanoscale investigations can answer critical tribological questions in the future.

The software package ESPEI has been developed for efficient evaluation of thermodynamic model parameters within the CALPHAD method. ESPEI uses a linear fitting strategy to parameterize Gibbs energy functions of single phases based on their thermochemical data and refines the model parameters using phase equilibrium data through Bayesian parameter estimation within a Markov Chain Monte Carlo machine learning approach. In this paper, the methodologies employed in ESPEI are discussed in detail and demonstrated for the Cu–Mg system down to 0 K using unary descriptions based on segmented regression. The model parameter uncertainties are quantified and propagated to the Gibbs energy functions.

One of the most promising nanoscale materials which fascinated researchers for the last few decades owing to its unique optoelectronics and physicochemical properties are carbon-based nanomaterials (CBNs). Various forms of CBNs have been developed such as single and multi-walled carbon nanotubes, graphene, fullerenes, nanodiamonds, and fluorescent carbon quantum dots (C-Dots) whereas each form is having its own exceptional properties owing to its dimensionalities and architectures. The advent of these unique classes of nanoscale materials opens up a spectrum of new opportunities and possibilities in employing these in emerging areas of biomedical. However, successful biomedical applications greatly rely on the likelihood of the comprehensive understanding of physicochemical interactions and biological responses of CBNs. Herein, we have tried to explore the ‘blood-CBNs’ interface by including the findings of recent studies. The role of surface modifications and functionalization in order to mitigate the adverse outcomes has also been incorporated.

This paper reports the molecular organization and mechanical properties of electrospun, post-drawn polyacrylonitrile (PAN) nanofibers. Without post-drawing, the polymer chain was kinked and oriented in hexagonal crystalline structures. Immediate post-drawing in the semi-solid state disrupted the crystal structures and chain kink at maximum draw ratio. Structural re-orientation at maximum draw resulted in a 500% increase in Young's modulus and a 100% increase in ultimate tensile strength. By applying post-drawing to electrospinning it may be possible to obtain PAN fibers and PAN-derived carbon fibers with enhanced mechanical properties compared to available fabrication technologies.

Insects have more than a million described species and represent more than half of all known living organisms. However, little is known about the operation and functions of the insect body, particularly their remarkable leg joints. This study is focused on partly filling this knowledge gap by using nanoindentation instruments to characterize the mechanical properties of leg joints from three different insects: a beetle, a mantis, and a dragonfly nymph. For all insect species, the tibia joint had the largest effective elastic moduli, followed by the femur joint, while the exocuticle had the smallest values.

A new protocol has been devised for determining elastic properties of natural biocomposites in the form of bivalve shells under wet and dry conditions. Four-point bending on shell slices of Mytilus edulis, Ensis siliqua, and Pecten maximus give generally lower and more reliable values of Young’s modulus, E, than those in the literature from three-point bending, due to the more even distribution of strain. Finite element analysis of the prismatic microstructure of Pinna nobilis, obtained by X-ray tomography, shows that values of E ≈ 20 GPa can be understood in terms of the real microstructure containing a small proportion of organic matrix phase with E ≈ 1 GPa and a dominant proportion of calcite with E ≈ 90 GPa. Higher values of E obtained by nanoindentation give results which are biased toward the properties of the carbonate phase rather than of the biocomposite as a whole.

A kind of n–p (SnO2)1.3/(α ∼ Bi2O3)x/(β ∼ Bi2O3)1−x nanocomposite (SB-15) was synthesized with polyvinyl alcohol (PVA) as a template by solid state synthesis. XRD and HR-TEM confirmed the formation of n–p (SnO2)1.3/(α ∼ Bi2O3)x/(β ∼ Bi2O3)1−x. Particle size is found to be about 18 nm from HR-TEM images. FE-SEM clearly detected the boundary between SnO2 nanoparticles and Bi2O3 polyhedron particles. The special morphology and coexisting of α-Bi2O3 and β-Bi2O3 in SB-15 make it have a stronger visible light absorption range as far as 725 nm. PL and photocurrent test shows that the SB-15 has the best photocarriers separation capability. About 99% decolorization ratio of Rh.B was achieved in only 5 min. About 70% Cr6+ was degraded within 20 min and it is about 60% for tetracycline in the coexisting system (Te with Cr6+ solution), introducing it as a promising photocatalytic material. This work has addressed the method of phase-selective synthesis of n–p SnO2/α ∼ Bi2O3/β ∼ Bi2O3 by convenient solid state synthesis, which should be useful for the studies of other composites.

Synthetic biology combines engineering and biology to produce artificial systems with programmable features. Specifically, engineered microenvironments have advanced immensely over the past few decades, owing in part to the merging of materials with biologic mimetic structures. In this review, the authors adapt a traditional definition of community ecology to describe “cellular ecology,” or the study of the distribution of cell populations and interactions within their microenvironment. The authors discuss two exemplar hydrogel platforms: (1) self-assembling peptide hydrogels and (2) poly(ethylene) glycol hydrogels and describe future opportunities for merging smart material design and synthetic biology within the scope of multicellular platforms.

Aluminum-doped zinc oxide (AZO) is one of the most promising transparent conductive oxide materials for a front electrode in solar cells. In this work, we roughened substrate surface and sputtered AZO films, where the effect of roughness on various AZO properties was investigated. The haze values were largely enhanced, retaining other important properties such as conductivity and transparency. The optical band gap exhibits a clear blue shift because of the roughness. The possible cause of this shift may be variation in the Al content due to the different deposition and post-annealing mechanisms of AZO films on the roughened surface.

The effective charge of an element is a parameter characterizing the electromigration effect, which can determine the reliability of interconnection in electronic technologies. In this work, machine learning approaches were employed to model the effective charge (z*) as a linear function of physically meaningful elemental properties. Average fivefold (leave-out-alloy-group) cross-validation yielded root-mean-square-error divided by whole data set standard deviation (RMSE/σ) values of 0.37 ± 0.01 (0.22 ± 0.18), respectively, and R2 values of 0.86. Extrapolation to z* of totally new alloys showed limited but potentially useful predictive ability. The model was used in predicting z* for technologically relevant host–impurity pairs.

Gelatin–chitosan–based scaffolds using different bioactive nano-ceramic phase such as hydroxyapatite (HAp), beta tri calcium phosphate (β-TCP) and 58 s bioactive glass (58 s BG) were fabricated at a fixed 30 wt% of bioceramic phase content. From FTIR spectrum of the composite scaffold, a red shift in amide I and amide II bonds from 1595 to 1545 cm−1 and a new absorption peak due to electrostatic interaction between Ca2+ and COO− were observed. Average pore size in all the composite scaffolds was in the range between 100 and 300 μm, significantly smaller than the average pore size of pure gelatin–chitosan scaffold. Gelatin–chitosan-58 s BG (GCB30) scaffold exhibited the highest amount of protein absorption of 23 mg/cm2 among all the prepared scaffolds after 36 h of incubation in bovine serum albumin (BSA) solution. Mesenchymal stem cell’s (MSC’s) proliferation onto GCB30 scaffold was significantly higher as compared to other prepared scaffolds up to 7 days of cell culture. Expression of both early marker (RUNX2) and late marker (Osteocalcin) of differentiation was higher in MSCs cultured onto GCB30 scaffold as compared to other prepared scaffolds.