The understanding of adhesion and survival behavior of bacterial pathogens on implant surfaces are critical to control and reduce implant-associated infections. Herein, the authors investigate the interactions of Staphylococcus aureus, one of the most prevalent causes of implant infections, with Mg–4Zn–0.5Ca implants. It was found that within 60 min of exposure, 99.1% of adherent bacteria were inactivated. The combination of unique mechanical properties, biodegradation kinetics, and antimicrobial characteristics of Mg–4Zn–0.5Ca alloy makes it a promising candidate for future implant applications.

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.

Insects are recognized with their ability to efficiently move, operate, and function, and hence are inspiration for the design of micromechanical systems. This work deals with the structural, mechanical, and frictional characterization of the leg joint articulations of the katydid (Orthoptera: Tettigoniidae). For the katydids, the tibia joints were found to show a nanosmooth texture while the femur joint had a micro/nanotextured surface characteristics. The nanotexture was a two-tone periodic patterns with the hierarchical structures involving cylindrical ridges that are covered with nanoscale lamellar patterns perpendicular to the long axis and valleys between ridges that are decorated with the hillock patterns. The tibia and femur contact regions showed the reduced elastic modulus (E r) values ranging from 0.88 ± 0.01 GPa to 3.90 ± 0.11 GPa. The friction coefficient (μ) value of 0.053 ± 0.001 was recorded for the sliding contact of the tibia joint against the femur joint in air under dry conditions. The low friction values are attributed to the reduced real area of contact between the joint pair due to the coupling of the nanosmooth surfaces against the hierarchically nanotextured surfaces.

Cellulose nanocrystals (CNCs) are high-strength sustainable nanomaterials, theincorporation of which to a host polymer matrix can potentially lead tonanocomposites with superior mechanical properties. However, the mismatch insurface energy of CNCs and common structural polymers is a challenge that needsto be overcome to prevent the aggregation of CNCs and ensure the robustintegration of CNCs into a polymer matrix. Herein, we report an approachinvolving the functionalization of CNCs with maleated-anhydride polypropylene(MAPP) through diethylenetriamine (DETA) linkers to significantly enhance thecompatibility between CNCs and polypropylene. Polypropylene/modified CNCnanocomposites displayed 74% and 76% increase in elastic modulus in comparisonto neat polypropylene and polypropylene/untreated CNC nanocomposites,respectively. The tensile strength was also higher for nanocomposites withmodified CNC than neat polypropylene, as well as nanocomposites with untreatedCNCs. The tensile strength at 5.5% strain of polypropylene/modified CNCnanocomposites was 32% and 28% larger that of polypropylene andpolypropylene/untreated CNC nanocomposites, respectively. Finally, suchCNC-based nanocomposites have a lower density than many competitive systemsresulting in opportunities to propagate this environmentally-responsibletechnology to nanocomposites used in additive manufacturing, automotiveapplications, construction materials and consumer products.

Accumulated body [1] approach to mitigate the effects of line edge roughness on bulk silicon finFETs and tri-gate FETs is analyzed through 3D TCAD simulations. A side-gate surrounding the body portion of the FET is used to accumulate the body with majority carriers. This approach is predicted to reduce device-to-device variability due to line edge roughness by stronger accumulation of the body in the wider sections of the channel and confinement of the channel away from the edges.

We describe experiments on self-heating and melting of nanocrystalline silicon microwires using single high-amplitude microsecond voltage pulses, which result in growth of large single-crystal domains upon resolidification. Extremely high current densities (>20 MA/cm2) and consequent high temperatures (1700 K) and temperature gradients (1 K/nm) along the microwires give rise to strong thermoelectric effects. The thermoelectric effects are characterized through capture and analysis of light emission from the self-heated wires biased with lower magnitude direct current/alternating current voltages. The hottest spot on the wires consistently appears closer to the lower potential end for n-type microwires and to the higher potential end for p-type microwires. The experimental light emission profiles are used to verify the mathematical models and material parameters used for the simulations. Good agreement between experimental and simulated profiles indicates that these models can be used to predict and design optimum geometry and bias conditions for current-induced crystallization of microstructures.

Nanocrystalline silicon (nc-Si) micro-bridges are melted and crystallized through Joule heating by applying high-amplitude short duration voltage pulses. Full crystallization of nc-Si bridges is achieved by adjusting the voltage-pulse amplitude and duration. If the applied pulse cannot deliver enough energy to the bridges, only surface texture modification is observed. On the contrary, if the pulse is not terminated after the entire bridge melts, molten silicon diffuses on to the contact pads and the bridge tapers in the middle. Melting of the bridges can be monitored through current-time (I-t) and voltage-time (V-t) measurements during the electrical stress. Conductance of the bridges is enhanced after the electrical stress.

Asymmetric melting was observed in electrically pulsed n-type (phosphorus) nanocrystalline silicon (nc-Si) wires fabricated lithographically. Scanning electron microscope (SEM) images taken from the pulsed wires showed that melting initiates from the ground terminal end of the wires instead of the center as initially expected. Asymmetry in the temperature profile is caused by heat exchanged between charge carriers and phonons when an electrical current is passed along a temperature gradient. This effect is known as Thomson effect, a thermoelectric heat transfer mechanism. One dimensional (1D) time dependent heat diffusion equation including Thomson heat term was solved to model the temperature profile on our structures. The modeling results show that Thomson effect introduces significant shifts in the temperature distribution. The effect of Thomson heat is modeled for various electrical pulse conditions and wires dimensions. Our results indicate that Thomson effect is significant in small scale electronic devices operating under high current densities.

We review experimental results—over the past 10–15 years and more recent theoretical modeling and computer simulations—on the effects of surface subnanoscale texture on adhesion and friction and the implications for certain mechanical properties of materials such as Mode I and Mode II failure. Examples and comparisons include surfaces that are adhesive or nonadhesive, rough or smooth, hard or soft (e.g., viscoelastic polymers), dry (unlubricated) or lubricated. One important conclusion is that the ultrafine picoscale details of a surface lattice or its roughness (“texture”) can be the most important factor in determining its friction and Mode II fracture, whereas such effects are less important for determining adhesion forces and Mode I fracture processes. Such studies are also clarifying the molecular and atomic basis of many well-established adhesion and tribological laws and empirical observations and are revealing new fundamental insights and relationships between nanoscale (molecular) and macroscale processes.