Nitrogen reactive ion etch processes for the selective removal of poly-(4-vinylpyridine) in block copolymer films.

Self-assembling block copolymer (BCP) patterns are one of the main contenders for the fabrication of nanopattern templates in next generation lithography technology. Transforming these templates to hard mark materials is key for pattern transfer and in some cases, involves selectively removing one block from the nanopattern. For poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP), a high χ BCP system which could be potentially incorporated into semiconductor nanofabrication, this selective removal is predominantly done by a wet etch/activation process. Conversely, this process has numerous disadvantages including lack of control and high generation of waste leading to high cost. For these reasons, our motivation was to move away from the wet etch process and optimise a dry etch which would overcome the limitations associated with the activation process. The work presented herein shows the development of a selective plasma etch process for the removal of P4VP cores from PS-b-P4VP nanopatterned film. Results have shown that a nitrogen reactive ion etch plasma has a selectivity for P4VP of 2.2:1 and suggest that the position of the nitrogen in the aromatic ring of P4VP plays a key role in this selectivity. In situ plasma etching and x-ray photoelectron spectrometry measurements were made without breaking vacuum, confirming that the nitrogen plasma has selectivity for removal of P4VP over PS.

Controlled solvent vapor annealing of a high χ block copolymer thin film.

Molecular self-assembling block copolymers (BCPs) have shown promise as a next generation bottom-up lithography technology. However, a critical step in advancing this approach is the elimination of polymer dewetting due to bulk solvent nucleation and thermodynamically driven film rupture that can occur during the solvent vapor annealing process. We report on the pattern formation via phase segregation of spin coated diblock copolymer films through the investigation of annealing parameters in the limit of high solvent vapor saturation conditions that results in wafer-scale patterning without observing polymer dewetting defects. Specifically, the work addresses polymer dewetting in diblock copolymer nanodot templates through the use of a "neutral" functionalization layer and the development of a custom-built solvent vapor annealing chamber to precisely control saturation conditions. Furthermore, the long anneal times (4 h) using a standard static solvent vapor annealing procedure were reduced to ∼15-30 minutes with our dynamic solvent vapor annealing system for the high χ, cylindrical forming poly(styrene)-block-poly(4-vinyl-pyridine) [PS-b-P4VP] diblock copolymer system. We discuss the kinetic mechanism governing the phase segregation process that highlights the small processing window bounded by long phase segregation timescales (≳1 min) on one side and the initiation of polymer film dewetting on the other. These results demonstrate a key step towards realizing a high fidelity, low cost BCP patterning technique for large-scale "bottom-up" feature definition at nanometer length scales.

Controlled degradation of polycaprolactone-based micropillar arrays.

Herein we demonstrate the fabrication of arrays of micropillars, achieved through the combination of direct laser writing and nanoimprint lithography. By combining two diacrylate monomers, polycaprolactone dimethacrylate (PCLDMA) and 1,6-hexanediol diacrylate (HDDA), two copolymer formulations that, owing to the varying ratios of the hydrolysable ester functionalities present in the polycaprolactone moiety, can be degraded in the presence of base in a controllable manner. As such, the degradation of the micropillars can be tuned over several days as a function of PCLDMA concentration within the copolymer formulations, and the topography greatly varied over a short space of time, as visualised using scanning electron microscopy and atomic force microscopy. Crosslinked neat HDDA was used as a control material, demonstrating that the presence of the PCL was responsible for the ability of the microstructures to degrade in the controlled manner. In addition, the mass loss of the crosslinked materials was minimal, demonstrating the degradation of microstructured surfaces without loss of bulk properties was possible. Moreover, the compatibility of these crosslinked materials with mammalian cells was explored. The influence of both indirect and direct contact of the materials with A549 cells was assessed by profiling indices reflective of cytotoxicity such as morphology, adhesion, metabolic activity, oxidative balance, and release of injury markers. No significant changes in the aforementioned profile were observed in the cells cultured under these conditions for up to 72 h, with the cell-material interaction suggesting these materials may have potential in microfabrication contexts towards biomedical application purposes.

A Review of Polylactic Acid as a Replacement Material for Single-Use Laboratory Components.

Every year, the EU emits 13.4 Mt of CO2 solely from plastic production, with 99% of all plastics being produced from fossil fuel sources, while those that are produced from renewable sources use food products as feedstocks. In 2019, 29 Mt of plastic waste was collected in Europe. It is estimated that 32% was recycled, 43% was incinerated and 25% was sent to landfill. It has been estimated that life-sciences (biology, medicine, etc.) alone create plastic waste of approximately 5.5 Mt/yr, the majority being disposed of by incineration. The vast majority of this plastic waste is made from fossil fuel sources, though there is a growing interest in the possible use of bioplastics as a viable alternative for single-use lab consumables, such as petri dishes, pipette tips, etc. However, to-date only limited bioplastic replacement examples exist. In this review, common polymers used for labware are discussed, along with examining the possibility of replacing these materials with bioplastics, specifically polylactic acid (PLA). The material properties of PLA are described, along with possible functional improvements dure to additives. Finally, the standards and benchmarks needed for assessing bioplastics produced for labware components are reviewed.

An investigation into the one-pot Heck olefination-hydrogenation reaction.

Herein is described an operationally simple process concerning the observation that, following either inter-, or intramolecular Heck olefination, stirring of the so formed substituted alkenyl product under an atmosphere of hydrogen efficiently effects alkene hydrogenation. Overall this two-operation, one-pot "reductive Heck" sequence is notable since direct reductive Heck processes, using additives such as formate salts, are restricted to a limited range of substrates. In total 25 examples are reported (yields ranging from 0 to 95%), which were selected in order to probe the scope and limitations of this method. Finally, the utility of this sequence was demonstrated in a short synthesis of the calcimimetic agent, cinacalcet.

Biomimetic Polymer Surfaces by High Resolution Molding of the Wings of Different Cicadas.

Recent studies have shown that insect wings have evolved to have micro- and nanoscale structures on the wing surface, and biomimetic research aims to transfer such structures to application-specific materials. Herein, we describe a simple and cost-effective method of replica molding the wing topographies of four cicada species using UV-curable polymers. Different polymer blends of polyethylene glycol diacrylate and polypropylene glycol diacrylate were used as molding materials and a molding chamber was designed to precisely control the x, y, and z dimensions. Analysis by scanning electron microscopy showed that structures ranged from 148 to 854 nm in diameter, with a height range of 191-2368 nm, and wing patterns were transferred with high fidelity to the crosslinked polymer. Finally, bacterial cell studies show that the wing replicas possess the same antibacterial effect as the cicada wing from which they were molded. Overall, this work shows a quick and simple method for patterning UV-curable polymers without the use of expensive equipment, making it a highly accessible means of producing microstructured materials with biological properties.

Replica molding of cicada wings: The role of water at point of synthesis on nanostructure feature size.

Many natural surfaces, including the wings of cicada insects, have shown to display bactericidal properties as a result of surface topography. Moreover, the size and distribution of the surface features (on the nano- and microscale) are known to influence the efficacy of the surface at inhibiting bacterial cell growth. While these types of natural surfaces illustrate the effect of structure on the bactericidal activity, a deeper understanding can be achieved by creating surfaces of different feature sizes. This is essential in order to understand the effects of changes of surface topography on bacteria-surface interactions. To this end, we have performed a series of replica molding processes of the wings of the Megapomponia Intermedia cicada to prepare wing replicas in polyethylene glycol (PEG), which possess the topographical features of the wing surface, with a minimum loss of feature resolution. Atomic force microscopy characterization of these patterned surfaces in both air and aqueous environments shows that by controlling the swelling characteristics of the PEG, we can control the ultimate swollen dimensions of the nanopillar structures on the surface of PEG. As a result, by using a single wing with an average nanopillar height of 220 nm, different patterned PEG samples with nanopillar heights ranging from 180 to 307 nm were produced.

Evaluation of the usefulness of an ELISA and protein electrophoresis in the diagnosis of Encephalitozoon cuniculi infection in rabbits.

OBJECTIVE-To evaluate the usefulness of an antibody detection ELISA and protein electrophoresis (PE) for diagnosing Encephalitozoon cuniculi (ECUN) infection in pet rabbits. ANIMALS-203 pet rabbits. PROCEDURES-Serum and plasma samples from pet rabbits were submitted from veterinary clinics within the United States. Participating veterinarians completed a questionnaire that was used to classify rabbits as clinically normal (n=33), suspected of having an ECUN infection (103), or clinically abnormal but not suspected of having an ECUN infection (67). An ELISA for detection of serum or plasma IgG against ECUN was developed by use of commercially available reagents. Results of the ELISA and PE were used to detect ECUN infection. RESULTS-A high seroprevalence of antibody against ECUN was detected in all 3 groups of rabbits. In rabbits suspected of having an ECUN infection, the mean IgG titer was 1.7 times as high as the values in the other rabbit groups. Rabbits suspected of having an ECUN infection and those that were simply clinically abnormal had a higher concentration of gamma-globulins than clinically normal rabbits. This increase in globulins concentration was accompanied by a decrease in the albumin-to-globulin ratio. Results of the ELISA and PE were significantly different between clinically normal rabbits and those suspected of having an ECUN infection. CONCLUSIONS AND CLINICAL RELEVANCE-The combination of an ELISA and PE may aid in the diagnosis of ECUN infection in pet rabbits. IMPACT FOR HUMAN MEDICINE-Because ECUN is a potential zoonotic agent, diagnostic methods for pet rabbits need to be improved to protect human health.

Diastereoselective functionalisation of benzo-annulated bicyclic sultams: Application for the synthesis of cis-2,4-diarylpyrrolidines.

The cis-dibromination of unsaturated bicyclic bridgehead sultams 5a and 5b, and experiments designed to understand the cis-stereochemical outcome of these reactions, are described. In the case of 5b, a novel solvent dependent carbocation rearrangement occurs with the formation of 18b. cis-Dibromides 13a and 13b undergo regioselective dehydrobromination, and the participation of the resultant vinyl bromide 24a in lithiation and Pd-coupling chemistry is described. In the case of the latter, hydrogenation of the styryl products afforded a single diastereoisomer. These compounds were then studied under dissolved metal reduction conditions, in which the cleavage of both N-S and C-S bonds takes place to afford cis-2,4-diaryl-substituted pyrrolidines 35-37.

Investigating the colloidal stability of fluorescent silica nanoparticles under isotonic conditions for biomedical applications.

Fluorescent silica nanoparticle (NP) labels are of great interest in biomedical diagnostics, however, when used in bioassays under physiological conditions they rapidly agglomerate and precipitate from solution leading to high levels of non-specific binding. In this work, using size and zeta-potential data obtained from Dynamic and Electrophoretic Light Scattering analysis, the improvement in colloidal stability of silica NPs under physiological conditions was correlated with an increase in the concentration of three additives: (1) a protein, bovine serum albumin (BSA); (2) a neutral surfactant, Tween 20®; and (3) a charged surfactant, sodium dodecyl sulfate (SDS). The number of BSA molecules present in the NP corona at each concentration was calculated using UV-Vis spectroscopy and a bicinchoninic acid protein assay (BCA). The optimal concentration of each additive was also effective in stabilizing antibody labeled fluorescent nanoparticles (αNPs) under physiological conditions. Using a fourth additive, trehalose, the colloidal stability of αNPs after freeze-drying and long-term storage also significantly improved. Both as-prepared and freeze-dried αNPs were tested in a standard fluorescence immunoassay for the detection of human IgG. The as-prepared assay showed a higher sensitivity at low concentration and a lower limit of detection when compared to a free dye assay. Assays performed with freeze dried αNPs after 4 and 22 days also showed good reproducibility.

Bacterial and parasitic diseases of rabbits.

Bacterial disease is common in pet rabbits; parasitic disease occurs as well but at a much lower frequency. Of these, bacterial diseases of the respiratory tract and dental structures are seen most commonly in practice. Successful treatment depends on positive diagnosis of the disease process and causative agent. This article focuses on the more common bacterial and parasitic diseases encountered in clinical practice.

Synthesis of tertiary benzamides via Pd-catalyzed coupling of arylboronic esters and carbamoyl chlorides.

Ortho-substituted arylboronic esters are efficiently coupled with carbamoyl chlorides under Pd-catalysis to give tertiary benzamides.