InterNano Nanomanufacturing Repository
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Ultrahigh Density Alignment of Carbon Nanotube Arrays by Dielectrophoresis
No full textWe report ultrahigh density assembly of aligned single-walled carbon nanotube (SWNT) two-dimensional arrays via AC dielectrophoresis using high-quality surfactant-free and stable SWNT solutions. After optimization of frequency and trapping time, we can reproducibly control the linear density of the SWNT between prefabricated electrodes from 0.5 SWNT/μm to more than 30 SWNT/μm by tuning the concentration of the nanotubes in the solution. Our maximum density of 30 SWNT/μm is the highest for aligned arrays via any solution processing technique reported so far. Further increase of SWNT concentration results in a dense array with multiple layers. We discuss how the orientation and density of the nanotubes vary with concentrations and channel lengths. Electrical measurement data show that the densely packed aligned arrays have low sheet resistances. Selective removal of metallic SWNTs via controlled electrical breakdown produced field-effect transistors with high current on−off ratio. Ultrahigh density alignment reported here will have important implications in fabricating high-quality devices for digital and analog electronics
Hybrid Top-Down and Bottom-Up Fabrication Approach for Wafer-Scale Plasmonic Nanoplatforms
No full textSynthesis of hydrogels via ring-opening metathesis polymerization: factors affecting gelation
No full textInforming Selection of Nanomaterial Concentrations for ToxCast In Vitro Testing based on Occupational Exposure Potential
No full textBackground: Little justification is generally provided for selection of in vitro assay testing concentrations for engineered nanomaterials (ENMs). Selection of concentration levels for hazard evaluation based on real-world exposure scenarios is desirable.
Objectives: Our goal is to use estimates of lung deposition following occupational exposure to nanomaterials to recommend in vitro testing concentrations for the U.S. Environmental Protection Agency’s ToxCastTM program. We provide testing concentrations for carbon nanotubes (CNTs), titanium dioxide (TiO2) and silver (Ag) nanoparticles.
Methods: We reviewed published ENM concentrations measured in air in manufacturing and R&D labs to identify input levels for estimating ENM mass retained in the human lung using the Multiple-Path Particle Dosimetry (MPPD) model. Model input parameters were individually varied to estimate alveolar mass retained for different particle sizes (5-1000 nm), aerosol concentrations (0.1, 1 mg/m3), aspect ratios (2, 4, 10, 167), and exposure durations (24 hours and a working lifetime). The calculated lung surface concentrations were then converted to in vitro solution concentrations.
Results: Modeled alveolar mass retained after 24 hours is most affected by activity level and aerosol concentration. Alveolar retention for Ag and TiO2 nanoparticles and CNTs for a working lifetime (45 years) exposure duration is similar to high-end concentrations (~ 30-400 μg/mL) typical of in vitro testing reported in the literature.
Conclusions: Analyses performed are generally applicable to provide ENM testing concentrations for in vitro hazard screening studies though further research is needed to improve the approach. Understanding the relationship between potential real-world exposures and in vitro test concentrations will facilitate interpretation of toxicological results
Universal Cyclic Polymer Templates
No full textTwo unique molecular templates for generating polymeric materials with a cyclic molecular architecture were developed by combining ring-expansion metathesis polymerization and click chemistry. These two universal cyclic polymers were used in three examples to demonstrate the wide range of potential materials enabled. They include functional cyclic polymers, cyclic polymer brushes, and cyclic gels
Additive-loaded EUV photoresists: performance enhancement and the underlying physics
No full textA series of molecular glasses (MGs) protected with multiple tert-butoxylcarbonylmethyl (tBCM) groups are employed as additives to enhance extreme ultra violet (EUV) photolithographic performance of a hydroxystyrene based Environmentally Stable Chemically Amplified Photoresist (ESCAP). The tBCM groups deprotect to form carboxylic acids that are capable of hydrogen bonding with chain segments of the polymer resist. This approach enables a systematic study of the governing physics underlying the improved lithographic performance. While MGs inhibit solubility in all cases, we find that differences in the structure of the MGs can significantly affect the photoacid diffusivity. In our ongoing optimization of the structure and loading of MGs, photoacid generators (PAGs), and base quenchers, 25 nm to 30 nm resolution has been achieved. The structure-property relationships and the synergistic effects of employing small, multi-functional additives in the polymeric photoresists are studied using various characterizations