Design rules for self-assembled block copolymer patterns using tiled templates

Directed self-assembly of block copolymers has been used for fabricating various nanoscale patterns, ranging from periodic lines to simple bends. However, assemblies of dense bends, junctions and line segments in a single pattern have not been achieved by using sparse templates, because no systematic template design methods for achieving such complex patterns existed. To direct a complex pattern by using a sparse template, the template needs to encode the key information contained in the final pattern, without being a simple copy of the pattern. Here we develop a set of topographic template tiles consisting of square lattices of posts with a restricted range of geometric features. The block copolymer patterns resulting from all tile arrangements are determined. By combining tiles in different ways, it is possible to predict a relatively simple template that will direct the formation of non-trivial block copolymer patterns, providing a new template design method for a complex block copolymer pattern.Samsung Scholarship FoundationSemiconductor Research CorporationTokyo Electron LimitedTaiwan Semicondcutor Manufacturing CompanyNational Science Foundation (U.S.) (Award DMR1234169

Evaluation of the cost and effectiveness of diverse recruitment methods for a genetic screening study

Purpose: Recruitment of participants from diverse backgrounds is crucial to the generalizability of genetic research, but has proven challenging. We retrospectively evaluated recruitment methods used for a study on return of genetic results. Methods: The costs of study design, development, and participant enrollment were calculated, and the characteristics of the participants enrolled through the seven recruitment methods were examined. Results: A total of 1118 participants provided consent, a blood sample, and questionnaire data. The estimated cost across recruitment methods ranged from $579 to$1666 per participant and required a large recruitment team. Recruitment methods using flyers and staff networks were the most cost-efficient and resulted in the highest completion rate. Targeted sampling that emphasized the importance of Latino/a participation, utilization of translated materials, and in-person recruitments contributed to enrolling a demographically diverse sample. Conclusions: Although all methods were deployed in the same hospital or neighborhood and shared the same staff, each recruitment method was different in terms of cost and characteristics of the enrolled participants, suggesting the importance of carefully choosing the recruitment methods based on the desired composition of the final study sample. This analysis provides information about the effectiveness and cost of different methods to recruit adults for genetic research

Assembly of Sub-10-nm Block Copolymer Patterns with Mixed Morphology and Period Using Electron Irradiation and Solvent Annealing

Block copolymer self-assembly generates patterns with periodicity in the ∼10–100 nm range and is increasingly recognized as a route to lithographic patterning beyond the resolution of photolithography. Block copolymers naturally produce periodic patterns with a morphology and length-scale determined by the molecular architecture, and considerable research has been carried out to extend the range of patterns that can be produced from a given block copolymer, but the ability to control the period of the pattern over a wide range and to achieve complex structures with mixed morphologies from a given block copolymer is limited. Here we show how patterns consisting of coexisting sub-10-nm spheres and cylinders and sphere patterns with a range of periods can be created using a combination of serial solvent anneal processes and electron-beam irradiation of selected areas of a film of poly(styrene-block-dimethylsiloxane). These techniques extend the capabilities of block copolymer lithography, enabling complex aperiodic nanoscale patterns to be formed from a single block copolymer thin film.Semiconductor Research CorporationUnited States. Office of Naval ResearchSingapore-MIT AllianceUniversity of California, Los Angeles. FENA Cente

Seeded solution growth of nanoparticles into ordered three-dimensional supracrystals

We report on a novel synthetic method for ordered three-dimensional nanoparticle supracrystals, which is based on seeded solution growth of nanoparticles. The present study provides a new platform for nanoparticle supracrystals to be efficiently fabricated and manipulated

Two-Dimensional Nanoparticle Supracrystals: A Model System for Two-Dimensional Melting

In a Langmuir trough, successive compression cycles can drive a two-dimensional (2D) nanoparticle supracrystal (NPSC) closer to its equilibrium structure. Here, we show a series of equilibrated 2D NPSCs consisting of gold NPs of uniform size, varying solely in the length of their alkanethiol ligands. The ordering of the NPSC is governed by the ligand length, thus providing a model system to investigate the nature of 2D melting in a system of NPs. As the ligand length increases the supracrystal transitions from a crystalline to a liquid-like phase with evidence of a hexatic phase at an intermediate ligand length. The phase change is interpreted as an entropy-driven phenomenon associated with steric constraints between ligand shells. The density of topological defects scales with ligand length, suggesting an equivalence between ligand length and temperature in terms of melting behavior. On the basis of this equivalence, the experimental evidence indicates a two-stage 2D melting of NPSCs

Aligned Sub-10-nm Block Copolymer Patterns Templated by Post Arrays

Self-assembly of block copolymer films can generate useful periodic nanopatterns, but the self-assembly needs to be templated to impose long-range order and to control pattern registration with other substrate features. We demonstrate here the fabrication of aligned sub-10-nm line width patterns with a controlled orientation by using lithographically formed post arrays as templates for a 16 kg/mol poly(styrene-block-dimethylsiloxane) (PS-b-PDMS) diblock copolymer. The in-plane orientation of the block copolymer cylinders was controlled by varying the spacing and geometry of the posts, and the results were modeled using 3D self-consistent field theory. This work illustrates how arrays of narrow lines with specific in-plane orientation can be produced, and how the post height and diameter affect the self-assembly.United States. Office of Naval ResearchNational Science Foundation (U.S.)Semiconductor Research CorporationUniversity of California, Los Angeles. Center on Functional Engineered Nano ArchitectonicsSamsung Electronics Co. (Scholarship foundation

Molecular biological and procedural optimization of the P450BM-3 based whole-cell biotransformation of alpha-pinene in an aqueous-organic two-phase process

Im Zentrum dieser Arbeit stand die Entwicklung eines wässrig-organischen Zweiphasenpro-zesses zur regio- und stereoselektiven Ganzzellbiotransformation eines apolaren und toxischen Terpens zu hochwertigen Produkten. Die Fünffachvariante V26T R47F A74G F87V L188K der katalytisch unabhängigen P450-Monooxygenase CYP102A1 (P450BM 3 QM) und das bizyklische Monoterpen (-)-alpha-Pinen wurden als Modellenzym bzw. –terpen verwendet, um die mikrobielle Ganzzellbiotransformation durch rekombinante Escherichia coli BL21 (DE3) Zellen zu untersuchen. Dabei konnten Produktausbeuten und Produktend-konzentrationen des wässrig-organischer Zweiphasenbioprozess sowohl durch prozesstechni-sche als auch molekularbiologische Optimierungen verbessert werden. P450BM 3 QM oxidiert in einer cofaktorabhängigen Reaktion (-)-alpha-Pinen zu (-)-alpha-Pinenoxid, (-)trans-Verbenol und (-)-Myrtenol mit einem Enantiomerenüberschuß >92%. Verbenol und Myrtenol fördern die Entkopplung der NADPH-Oxidation von der Substratoxidation und hemmen dadurch P450BM 3 QM kompetitiv. Zusätzlich zu diesem Phänomen machte die Instabilität von alpha-Pinenoxid in wässriger Lösung eine interne in situ Produktabtrennung durch Extraktion in eine organische Trägerphase, die im direkten Kontakt mit dem Ganzzellbiokata-lysator steht und gleichzeitig als Substratreservoir dient, notwendig. Im Erlenmeyerkolben mit reinem (-)-alpha-Pinen als organische Phase konnten einige prozessrele-vante Parameter, wie toxische Einflüsse einer alpha-Pinenphase auf E. coli, identifiziert werden. Durch Expression eines Glucosefacilitators (GLF) aus Zymomonas mobilis und einer Glucosedehydrogenase (GlcDH) aus Bacillus megaterium konnte ein, auf extrazellulär vorliegender Glucose basierendes, intrazelluläres Cofaktorregenerationssystem eingeführt werden und dessen positiver Einfluss auf die spezifische Produktausbeute YP/X und die spezifische initiale Produktbildungsrate Q beschrieben werden. Bei Verwendung eines Ganzzellbiokatalysators mit rekombinanter Cofaktorregenerierung konnte YP/X um das Sechs- und Q um das Neunfache gesteigert werden. Bei der prozesstechnischen Optimierung des Zweiphasenbioprozesses konnte, durch Einführung von Diisononylphthalat (DINP) als organische Trägerphase für das Substrat alpha-Pinen, eine Verbesserung der Biokompatibilität der organischen Phase und dadurch eine Verlängerung des Produktbildungszeitraums auf über 4 h erreicht werden. Weitere prozessrelevante Parameter wie Rührerdrehzahl, Volumen der organischen Phase und Anteil des Substrats alpha-Pinen in der organischen Phase wurden identifiziert und optimiert. Die Kombination prozesstechnischer und molekularbiologischer Optimierungen führte zu bisher in der Literatur nicht beschriebenen Konzentrationen für die biokatalytische Oxidation von alpha-Pinen von über 1 g l 1 oxidierte Produkte bezogen auf das Volumen der wässrigen Phase nach 4 h Biotransformationszeit. Diese Produktausbeuten stellen einen weiteren Schritt zur Etablierung industrieller Verfahren zur biologischen Wertschöpfung auf Basis von Terpenen dar.A recombinant E. coli BL21 (DE3) strain overexpressing a variant of P450BM-3 (V26T/R47F/A74G/F87V/L188K) oxyfunctionalizes the bicyclic monoterpene alpha-pinene to alpha-pinene oxide, verbenol and myrtenol. To address the low water solubility and the toxicity of terpenoids an aqueous-organic two-phase bioprocess was developed. Diisononyl phthalate (DINP) was selected as a biocompatible organic carrier solvent capable of masking the toxic effects mediated by alpha-pinene and of efficiently extracting the products enabling scale-up to the bioreactor. With an aqueous to organic phase ratio of 3:2 and 30 % (v/v) of alpha-pinene in the organic phase a biocatalytic product formation period of more than 4 hours was achieved. A comparison of the biotransformation performance of BL21 (P450BM 3 QM) and a strain with an additional heterologous NADPH regeneration system comprising glucose facilitator and dehydrogenase, but only expressing half the amount of P450BM-3 QM, shows comparable product concentrations of 1020±144 and 800±61 mg l-1Aq, respectively. The total product yields YP/P450 (µmol µmol 1P450) were 80 % higher when the strain with the cofactor regeneration system was used. A total product concentration of over 1 g lAq-1, corresponding to the highest value reported for microbial alpha-pinene oxyfunctionalization so far, marks a promising step forward towards a future application of recombinant microorganisms for the selective oxidation of terpenoids to value-added products

Aligned Sub-10-nm Block Copolymer Patterns Templated by Post Arrays

Self-assembly of block copolymer films can generate useful periodic nanopatterns, but the self-assembly needs to be templated to impose long-range order and to control pattern registration with other substrate features. We demonstrate here the fabrication of aligned sub-10-nm line width patterns with a controlled orientation by using lithographically formed post arrays as templates for a 16 kg/mol poly(styrene-block-dimethylsiloxane) (PS-<i>b</i>-PDMS) diblock copolymer. The in-plane orientation of the block copolymer cylinders was controlled by varying the spacing and geometry of the posts, and the results were modeled using 3D self-consistent field theory. This work illustrates how arrays of narrow lines with specific in-plane orientation can be produced, and how the post height and diameter affect the self-assembly