Flow controlled solvent vapor annealing of block copolymers for lithographic applications

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 185-192).Self-assembly of block copolymer thin-films may provide an inexpensive alternative to patterning lithographic features below the resolution limits of traditional optical methods. Block copolymers (BCPs) are polymers made of two or more distinct monomer/block units that are covalently bonded. Due to their differences in surface energy, the different blocks tend to phase segregate like oil and water; but because of the covalent linkage, this segregation is practically limited to size scales ranging from only a few nm to ~ 100 nm. A thin film of a BCP can be used in much the same way as a photoresist in the lithographic process, whereas a desired pattern morphology can be obtained by etching one block away and leaving behind a self-assembled hard mask for the underlying substrate. After a thin film of BCP is coated onto a given substrate, the BCP must be given an annealing step, where the disordered entangled polymer networks can be allowed to diffuse and equilibrate into lower free energy configurations which result in periodic patterns of micelles with different morphologies such as spheres, in/out of plane cylinders, etc. This work explored the technique of solvent vapor annealing, where organic solvents were allowed to interact with BCP thin films to facilitate annealing and act as surrogates for the different BCP polymer blocks. This allowed for a wide range of control over the BCP self-assembly (morphology, periodicity, etc.) for a given molecular weight BCP. Additionally, by adding heat at critical times during the self-assembly, time scales for solvent vapor enhanced self-assembly could be reduced from hours to seconds making the prospects for this technology to become industrially applicable more promising.by Kevin Willy Gotrik.Ph.D

In Vitro Directed Evolution of Fluorescence-Enhancing and Structure-Switching RNA Aptamers

Genetically-encoded fluorescent proteins have become an essential tool, and researchers today have access to a diverse array of protein-labeling strategies for studying fundamental \textit{in vivo} processes. However, there exist relatively few methods for \textit{in vivo} detection of an equally important biomolecule – RNA. One useful method to track RNA entails fusing the cellular RNA of interest to an RNA aptamer that can bind to and “turn on” the fluorescence of a small-molecule dye. Unfortunately, it is difficult to discover such fluorescence-enhancing RNA aptamers. This is because the conventional method of aptamer discovery (SELEX) can enrich for RNA that binds to a dye, but it does not preferentially identify sequences that generate a fluorescent signal upon binding. Thus, there is a critical need for a method capable of directly screening RNA aptamers for fluorescence enhancement. To address this need, we have developed a strategy for rapidly and intently screening large numbers of RNA aptamers based on their capacity to generate a fluorescent signal upon binding a small-molecule dye. Our approach generates libraries of Gene-linked RNA Aptamer Particles (GRAPs) that display functional RNA aptamers and are isolatable using fluorescence-activated cell sorting (FACS). As proof of concept, we performed selections isolating fluorescence-enhancing aptamers against malachite green (MG). We show that by directly selecting for function rather than binding, we can isolate RNA aptamers that are brighter and higher affinity than the best known MG aptamer. GRAP display also enables us to measure the fluorescence signal of every aptamer across multiple emission windows, permitting us to reconstruct the emission profile of every displayed aptamer. This in turn, allows us to intentionally isolate aptamers that fluoresce at a variety of wavelengths upon binding their target dye. Lastly, this technique can be used to discover functional RNA that undergoes a structural re-organization upon ligand binding. This has promising implications in the fields of biosensing, gene therapy, and cellular computing. This flexibility should greatly expand the toolbox of reagents available for studying RNA in vivo

Rectangular Symmetry Morphologies in a Topographically Templated Block Copolymer

Using an array of majority-block-functionalized posts makes it possible to locally control the self-assembly of a block copolymer and achieve several morphologies on a single substrate. A template consisting of a square symmetry array of posts produces a square-symmetry lattice of microdomains, which doubles the areal density of features.Semiconductor Research CorporationFENA CenterSemiconductor Research Corporation. Nanoscale Research InitiativeSingapore-MIT AllianceNational Science Foundation (U.S.)Taiwan Semiconductor Manufacturing CompanyTokyo Electron LimitedNational University of Singapor

Sacrificial-Post Templating Method for Block Copolymer Self-Assembly

A sacrificial-post templating method is presented for directing block copolymer self-assembly to form nanostructures consisting of monolayers and bilayers of microdomains. In this approach, the topographical post template is removed after self-assembly and therefore is not incorporated into the final microdomain pattern. Arrays of nanoscale holes of different shapes and symmetries, including mesh structures and perforated lamellae with a bimodal pore size distribution, are produced. The ratio of the pore sizes in the bimodal distributions can be varied via the template pitch, and agrees with predictions of self consistent field theory.Semiconductor Research CorporationFENA CenterSemiconductor Research Corporation. Nanoscale Research InitiativeSingapore-MIT AllianceNational Science Foundation (U.S.)Tokyo Electron LimitedTaiwan Semicondcutor Manufacturing Compan

Development and Applications of Fluorogen/Light-Up RNA Aptamer Pairs for RNA Detection and More.

The central role of RNA in living systems made it highly desirable to have noninvasive and sensitive technologies allowing for imaging the synthesis and the location of these molecules in living cells. This need motivated the development of small pro-fluorescent molecules called "fluorogens" that become fluorescent upon binding to genetically encodable RNAs called "light-up aptamers." Yet, the development of these fluorogen/light-up RNA pairs is a long and thorough process starting with the careful design of the fluorogen and pursued by the selection of a specific and efficient synthetic aptamer. This chapter summarizes the main design and the selection strategies used up to now prior to introducing the main pairs. Then, the vast application potential of these molecules for live-cell RNA imaging and other applications is presented and discussed.journal article2020importe

In Vitro Directed Evolution of Fluorescence-Enhancing and Structure-Switching RNA Aptamers

Genetically-encoded fluorescent proteins have become an essential tool, and researchers today have access to a diverse array of protein-labeling strategies for studying fundamental \textit{in vivo} processes. However, there exist relatively few methods for \textit{in vivo} detection of an equally important biomolecule – RNA. One useful method to track RNA entails fusing the cellular RNA of interest to an RNA aptamer that can bind to and “turn on” the fluorescence of a small-molecule dye. Unfortunately, it is difficult to discover such fluorescence-enhancing RNA aptamers. This is because the conventional method of aptamer discovery (SELEX) can enrich for RNA that binds to a dye, but it does not preferentially identify sequences that generate a fluorescent signal upon binding. Thus, there is a critical need for a method capable of directly screening RNA aptamers for fluorescence enhancement. To address this need, we have developed a strategy for rapidly and intently screening large numbers of RNA aptamers based on their capacity to generate a fluorescent signal upon binding a small-molecule dye. Our approach generates libraries of Gene-linked RNA Aptamer Particles (GRAPs) that display functional RNA aptamers and are isolatable using fluorescence-activated cell sorting (FACS). As proof of concept, we performed selections isolating fluorescence-enhancing aptamers against malachite green (MG). We show that by directly selecting for function rather than binding, we can isolate RNA aptamers that are brighter and higher affinity than the best known MG aptamer. GRAP display also enables us to measure the fluorescence signal of every aptamer across multiple emission windows, permitting us to reconstruct the emission profile of every displayed aptamer. This in turn, allows us to intentionally isolate aptamers that fluoresce at a variety of wavelengths upon binding their target dye. Lastly, this technique can be used to discover functional RNA that undergoes a structural re-organization upon ligand binding. This has promising implications in the fields of biosensing, gene therapy, and cellular computing. This flexibility should greatly expand the toolbox of reagents available for studying RNA in vivo

Analyse og prosjektering av tak strukturen av en velodrome

Oppgaven omhandler hvordan å analysere og prosjektere tak strukturen for en velodrome. I oppgaven er det brukt håndberegninger samt FEM-analyse program og BIM-program for å oppnå resultatene.This bachelor thesis is based on how to analyze and design the roof structure for a velodrome with the use of hand calculations, FEM-analysis software and BIM software to achieve the results

Kapitalstruktur och lönsamhet : En studie av svensk elektronikindustri

Bakgrund Forskning kring kapitalstrukturens betydelse för företagens lönsamhet är splittrad då olika studier visar på olika samband. Detta beror på att det är många andra faktorer utöver kapitalstrukturen som påverkar lönsamheten, likväl som det förekommer faktorer som påverkar kapitalstrukturen i sig. Dessa faktorer är i många fall dolda och manifesteras istället i resultatet, och dessa skiljer sig åt mellan branscher, länder och andra företagsspecifika särdrag. Svensk elektronikindustri är den del av svensk industri som uppvisat störst tillväxt de senaste två decennierna samtidigt som den utgör en viktig del av svenskt näringsliv. Det faktum att tidigare forskning är blandad i kombination med att det saknas studier som enbart fokuserar på denna bransch i detta land uppstod ett intresse av att fastställa förhållandet mellan kapitalstruktur och lönsamhet för denna bransch. Kunskap om detta kan vara till hjälp för ägare och chefer i företag inom denna bransch när de ska fatta beslut som rör kapitalstruktur. Syfte Syftet med denna uppsats är att fastställa hur lönsamheten förhåller sig till kapitalstrukturen inom svensk elektronikindustri. Metod Uppsatsen använder sig av linjär regressionsanalys för att undersöka sambandet mellan kapitalstruktur och lönsamhet. De beroende variablerna som använts i regressionsanalysen har varit två olika lönsamhetsmått: avkastning på totalt kapital, ROA, och avkastning på eget kapital, ROE. De oberoende variablerna har utgjorts av tre olika skuldsättningsmått: kortfristig, långfristig respektive total skuldsättning. Som kontrollvariabler har omsättning och balansomslutning använts.   Slutsats Empirin visar ett negativt förhållande mellan kortfristig, långfristig respektive total skuldsättning och lönsamhet när det mäts som ROA. När ROE används som lönsamhetsmått visade sig analysmodellen vara dåligt anpassad till att hantera datan, därmed gick det ej att dra några fullständiga slutsatser kring förhållandet mellan ROE och skuldsättning

Solvothermal Annealing of Block Copolymer Thin Films

A two-stage annealing process for block copolymer films was introduced consisting of a solvent vapor exposure followed by a thermal cycle. By heating the film but not the chamber, changes in the ambient vapor pressure of the solvent were avoided. Films of block copolymers and homopolymers showed transient nonmonotonic swelling behavior immediately after solvent exposure that was dependent on how the thin film was cast before the anneal. Thermal cycling of the solvent-swelled block copolymer films during the solvent vapor anneal (SVA) caused the films to deswell in 1–10 s and produced well-ordered microdomains in templated 45.5 and 51.5 kg/mol polystyrene-block-polydimethylsiloxane films annealed in toluene and <i>n</i>-heptane vapors for total process times of 30 s to 5 min