A simple atomic force microscope-based method for quantifying wear of sliding probes.

Sliding wear is particularly problematic for micro- and nano-scale devices and applications, and is often studied at the small scale to develop practical and fundamental insights. While many methods exist to measure and quantify the wear of a sliding atomic force microscope (AFM) probe, many of these rely on specialized equipment and/or assumptions from continuum mechanics. Here we present a methodology that enables simple, purely AFM-based measurement of wear, in cases where the AFM probe wears to a flat plateau.

Production of tunable nanomaterials using hierarchically assembled bacteriophages.

Large-scale fabrication of precisely defined nanostructures with tunable functions is critical to the exploitation of nanoscience and nanotechnology for production of electronic devices, energy generators, biosensors, and bionanomedicines. Although self-assembly processes have been developed to exploit biological molecules for functional materials, the resulting nanostructures and functions are still very limited, and scalable synthesis is far from being realized. Recently, we have established a bacteriophage-based biomimetic process, called 'self-templating assembly'.

Aquatic toxicity of photo-degraded insensitive munition 101 (IMX-101) constituents.

Insensitive munitions are desirable alternatives to historically used formulations, such as 2,4,6-trinitrotoluene (TNT), because of their so-called insensitivity to unintended detonation. The insensitive munition IMX-101 is a mixture of 2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), and nitroguanidine (NQ). Environmental releases of munitions may be from production wastewaters or training; these munitions may be exposed to ultraviolet (UV) light.

Nanosilver conductive ink: A case study for evaluating the potential risk of nanotechnology under hypothetical use scenarios.

Engineered nanomaterials (ENMs) are being incorporated into a variety of consumer products due to unique properties that offer a variety of advantages over bulk materials. Understanding of the nano-specific risk associated with nano-enabled technologies, however, continues to lag behind research and development, registration with regulators, and commercialization. One example of a nano-enabled technology is nanosilver ink, which can be used in commercial ink-jet printers for the development of low-cost printable electronics.

A weight-of-evidence approach to identify nanomaterials in consumer products: a case study of nanoparticles in commercial sunscreens.

Nanoscale ingredients in commercial products represent a point of emerging environmental concern due to recent findings that correlate toxicity with small particle size. A weight-of-evidence (WOE) approach based upon multiple lines of evidence (LOE) is developed here to assess nanomaterials as they exist in consumer product formulations, providing a qualitative assessment regarding the presence of nanomaterials, along with a baseline estimate of nanoparticle concentration if nanomaterials do exist. Electron microscopy, analytical separations, and X-ray detection methods were used to identify and characterize nanomaterials in sunscreen formulations.

Characterization of multi-layered fish scales (Atractosteus spatula) using nanoindentation, X-ray CT, FTIR, and SEM.

The hierarchical architecture of protective biological materials such as mineralized fish scales, gastropod shells, ram's horn, antlers, and turtle shells provides unique design principles with potentials for guiding the design of protective materials and systems in the future. Understanding the structure-property relationships for these material systems at the microscale and nanoscale where failure initiates is essential. Currently, experimental techniques such as nanoindentation, X-ray CT, and SEM provide researchers with a way to correlate the mechanical behavior with hierarchical microstructures of these material systems1-6.

Determination of nanosilver dissolution kinetics and toxicity in an environmentally relevant aqueous medium.

Assessing the dissolution of silver nanoparticles (AgNPs) in laboratory test media and in the aquatic environment is critical for determining toxicity. In the present study, the ion-release kinetics for 20-nm, 50-nm, and 80-nm AgNPs in environmentally relevant freshwaters with different electrical conductivity values (30 µS/cm, 150 µS/cm) were examined and related to the associated impact on Daphnia magna. The acute toxicity of the AgNP suspensions to D.

Testing of various membranes for use in a novel sediment porewater isolation chamber for infaunal invertebrate exposure to PCBs.

In benthic sediment bioassays, determining the relative contribution to exposure by contaminants in overlying water, porewater, and sediment particles is technically challenging. The purpose of the present study was to assess the potential for membranes to be utilized as a mechanism to allow freely dissolved hydrophobic organic contaminants into a pathway isolation exposure chamber (PIC) while excluding all sediment particles and dissolved organic carbon (DOC). This investigation was conducted in support of a larger effort to assess contaminant exposure pathways to benthos.

Determination of isoelectric points and the role of pH for common quartz crystal microbalance sensors.

Isoelectric points (IEPs) were determined by the method of contact angle titration for five common quartz crystal microbalance (QCM) sensors. The isoelectric points range from mildly basic in the case of Al2O3 sensors (IEP = 8.7) to moderately acidic for Au (5.