Dissertations / Theses on the topic 'Poly(dimethyl siloxane)'

This thesis focuses on the design, fabrication and characterization of polymeric smart structures that are able to alter their geometry and thus their properties upon the application of external stimuli in a reversible and controllable manner. Two different responsive structures are studied that both contain poly dimethyl-siloxane (PDMS) and differ in the design, geometry, and actuation mechanism. The first structure is a surface decorated by a square array of posts (cilia) made of PDMS reinforced with magnetic particles and is actuated magnetically. The structures are meant to mimic cilia, a hair-like structure found in nature. The physical parameters necessary for the magnetic response of the cilia including physical dimensions and filler concentration are investigated. In addition, the elastic modulus of the composites is measured and the microstructure is examined in order to determine the dispersion and homogeneity of the composites. The second structure is a planar hetero-structure consisting of a PDMS substrate and a nanoporous (NP) metal foam film which is actuated thermally or chemically by tuning the generation and release of residual stresses at the NP metal foam/PDMS interface. The effect of strain, applied to the PDMS substrate prior to the deposition of the NP metal foam and the effect of the PDMS and NP metal foam thicknesses on the shape/size of the planer hetero-structure after the actuation is investigated.

Poly (Dimethyl siloxane) thin films were prepared by solvent evaporation method in porous alumina hosts. The thickness of these layers ranged from multilayer to sub-monolayer. Different NMR methods (FFC relaxometry, transverse relaxation, 1H Double quantum NMR) were applied to study the dynamics and order in these thin films. We found that dynamic restrictions and order increased with decreasing layer size. The increase of a short component of T2 from CPMG curves was attributed to the thawing of the adsorbed chains as seen in the decrease of the short component from Hahn echoes.

Poly (Dimethyl siloxane) thin films were prepared by solvent evaporation method in porous alumina hosts. The thickness of these layers ranged from multilayer to sub-monolayer. Different NMR methods (FFC relaxometry, transverse relaxation, 1H Double quantum NMR) were applied to study the dynamics and order in these thin films. We found that dynamic restrictions and order increased with decreasing layer size. The increase of a short component of T2 from CPMG curves was attributed to the thawing of the adsorbed chains as seen in the decrease of the short component from Hahn echoes.

The main objectives of this thesis are 1) to evaluate the effect of cross-linking polar cyano phenyl (CN) groups on poly (dimethyl siloxane) (PDMS) and 2) to characterize the electromechanical properties of the resulting CN-PDMS blend as an electroactive actuator. Materials responding to an external stimulus are referred to as electroactive materials. There are several phenomena, which govern the mechanism in these materials, such as piezoelectricity, Maxwell's effect, ferroelectricity, electrostriction to name a few. These electroactive materials can be employed in several applications such as biomedical devices, robots, MEMs, aerospace vehicles, where the application is governed by the specific mechanism. However in order for the materials to be used effectively, they need to be thoroughly characterized to understand their behavior under factors like electric field, temperature, frequency and time.The present work focuses on developing an electroactive actuator, which has tailorable properties, allowing a wide operational temperature window from -100°C to 200°C and stability in harsh conditions. The characterization of the CN-PDMS polymer blend is done in two folds. First the physical properties of the polymer system are characterized by performing tests such as Dielectric Spectroscopy, Differential Scanning Calorimetery and Thermally Stimulated Current measurement. These techniques offer complete understanding of the structure-property relationship and effects of the functional groups on the dielectric and relaxation behavior of the polymer. The Dielectric Spectroscopy and the Thermally Stimulated Current analysis are used to elucidate the primary and the secondary relaxations, such as molecular mobility, interfacial polarization and dipolar relaxation. Dielectric Spectroscopy reveals that the molecular weight of PDMS does not affect the dielectric permittivity of the polymer blend. Also, Dielectric Spectroscopy clarifies the role of the CN polar group in the polarization of the CN-PDMS blend, inducing electromechanical strain in the polymer blend through electrostriction.The Differential Scanning Calorimetery is used to quantify the thermal behavior of the CN-PDMS polymer blend by quantifying properties such as melting temperature (Tm) and re-crystallization temperature of the PDMS polymer cross-linked with CN functional group. Results reveal that the thermal characteristics of the blend are not affected when PDMS is cross-linked with the functional CN moieties, meaning CN-PDMS maintains the advantages of PDMS in terms of stability towards harsh conditions, wide operating temperature and resistance to ultraviolet radiations.Following the physical characterization, electromechanical characterization of the CN-PDMS polymer blend is done to assess the electromechanical strain induced in the blend in response to electric field. The electromechanical strain is studied in two configurations; the electromechanical strain induced along the length of the polymer blend and induced through the thickness of the blend. These strain measurements are performed by applying both direct current as well as alternating current electric fields, and the induced electromechanical strain is studied as a function of amplitude and frequency of the electric field as well as the time of application of the electric field. The mechanism behind the development of the electromechanical strain and the nature of the strain under electric field is elucidated. The performance of the electroactive polymer is compared with several other polymeric actuators such as PVDF and PVDF-TrFE, polyurethane based actuators and ionomers. Comparison gives favorable results in terms of strains. In addition, CN-PDMS polymer system has the advantage of allowing control of processing of the blend, which is not present in all the other commercial electroactive polymers. The maximum electromechanical strain yielded along the length of the CN-PDMS polymer blend is 1.74 % when an electric field of 0.2MV/m is applied along the length of the polymer. Through the thickness, the maximum induced strain is 0.12 % for an electric field of 0.8 MV/m. Based on the nature of the strain yielded it is observed that the strain induced in the CN-PDMS blend is consistently proportional to the square of the electric field (E2). Moreover, the strain is driven by the concentration of the dipolar moieties (CN) present in the polymer blend.All the above-mentioned techniques used for thermal and electromechanical characterization of the CN-PDMS polymer blend illustrate the electrostrictive nature of the polymer under the study.

The objectives of this project were to investigate synthetic routes to form block copolymers of polyethersulphone and polydimethylsiloxane, linked through =Si-C= bonds. The work carried out has included the synthesis and characterisation of hydroxyl terminated polyethersulphone oligomers (PES). This material has then been quantitatively functionalised to give vinyl ended PES. A number of hydride terminated polydimethylsiloxane oligomers (PDMS) have also been synthesised and characterised. These materials have been successfully functionalised with epoxy groups through a vinyl addition reaction in the presence of chloroplatinic acid catalyst, incorporating the =Si-C= bond into the PDMS.These polymers, along with purchased carboxy propyl PDMS allowed the investigation of three principle routes to PES/PDMS copolymers (i) the catalysed addition reaction of vinyl PES with hydride terminated PDMS. (ii) the reaction of hydroxyl terminated PES with epoxy functionalised PDMS. (iii) the condensation reaction of hydroxyl terminated PES with carboxy propyl PDMS in the presence of stannous octoate catalyst. All three routes produce (A-B)[n] PES/PDMS block copolymers linked through =Si-C= bonds. Due to the large difference in solubility parameters between PES and PDMS homopolymers, there is great difficulty in producing a homogeneous solution of the reacting polymers. A wide range of solvent systems were investigated before 1,1,2,2-tetrachloroethane (TCE) was found to be the most suitable. Routes (i) and (ii) were investigated as solution reactions in TCE and the reaction products characterised by proton nuclear magnetic resonance spectroscopy (1-H nmr) and differential scanning calorimetry (dsc). Both reactions showed only limited success. Route (iii) could not be investigated in solution as a homogeneous solution of the oligomers could not be formed. All three synthetic routes were investigated as reactions in the melt and the products characterised by 1-H nmr and dsc. Routes (ii) and (iii) proving to be the more successful. All three reaction schemes were examined extensively using model compounds and short chain polymeric oligomers and were shown to be suitable routes to form the required block copolymers.

Im Rahmen der vorliegenden Arbeit werden die Synthese und Charakterisierung eines thermisch-kontrollierten und eines photochemisch-kontrollierten reversiblen Polymersystems vorgestellt. Weiterhin werden Poly(dimethyl)siloxan-Oberflächen mit Amino-, Isocyanat-, Furan-, Maleimid- und Cumarin-Gruppen funktionalisiert. Hierbei werden sowohl bekannte als auch neuartige Wege der Oberflächenmodifizierung vergleichend untersucht und bewertet. Ausgehend von den hergestellten Cumarin-funktionalisierten Poly(dimethyl)siloxan-Oberflächen wird eine Anbindung des synthetisierten photochemisch-kontrollierten reversiblen Polymersystems an diese Oberflächen untersucht. Des Weiteren wird die Anbindung des synthetisierten thermisch kontrollierten reversiblen Polymersystems sowohl an den hergestellten Maleimid- als auch an den Furan-funktionalisierten Poly(dimethyl)siloxan-Oberflächen analysiert. Basierend auf den vorgestellten Cumarin-Funktionalisierungen werden photoaktive Oberflächen beschrieben und mittels ATR-IR-spektroskopischer und UV/Vis-spektroskopischer Methoden analysiert.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
This report describes the fabrication of devices in poly(dimethyl)siloxane (PDMS) for colorimetric determination of ethanol in whisky. The devices were fabricated via 3D printing and used to perform colorimetric assays with image detection using a scanner. The PDMS devices were evaluated comparing the results obtained from the water aliquot scans by extracting the pixel intensities in the RGB channel, where there was no statistical difference for a confidence level of 0.05. The iron complexation reaction with 1,10-phenanthroline was also evaluated by comparing the results of two different devices. Ferrous ammonium sulphate solutions were used at concentrations of 0,1 to 10 mg.L -1 , where correlation curves were obtained from the pixels intensities extracted in the yellow channel. The obtained equations were used to estimate the concentration of a known iron solution of 8 mg.L -1 , obtaining a difference of 0.74% between the results of both devices. The oxidation reaction of ethanol with potassium dichromate was used to determine ethanol in samples of seized whiskeys by Federal Police. It was possible to determine ethanol in the range of 0% to 60% (v/v), using a gray color channel for the concentration range of 0% to 20% (v/v) with R 2 = 0.993, with a detection limit of 0,86% and quantification limit of 1.44% and the yellow color channel for the concentration range of 20% to 60% (v/v) with R 2 = 0.998. It was possible to determine the ethanol content in 66 samples of seized whiskeys. Where 53 samples were discriminated as falsified and 13 samples were not discriminated from original samples based on the ethanol content.
O presente trabalho descreve a fabricação de dispositivos em poli(dimetil)siloxano (PDMS) para determinação colorimétrica de etanol em uísques. Os dispositivos foram fabricados via impressão 3D e utilizados para a realização de ensaios colorimétricos com detecção por imagem a partir de um scanner de mesa. Os dispositivos de PDMS foram avaliados comparando os resultados obtidos de digitalizações de alíquotas de água extraindo as intensidades de pixel no canal RGB,onde não houve diferença estatística para um nível de confiança de 0,05. Foi avaliado também a reação de complexação do ferro com a 1,10 fenantrolina comparando os resultados de dois dispositivos diferentes. Foram utilizadas soluções sulfato ferroso amoniacal nas concentrações de 0,1 até 10 mg.L -1 , onde foram obtidas curvas de correlação para as intensidades de pixels extraídas no canal amarelo. As equações obtidas foram utilizadas para estimar a concentração de uma solução conhecida de ferro de 8 mg.L -1 , obtendo-se uma diferença de 0,74% entre os resultados dos dois dispositivos. A reação de oxidação de etanol com dicromato de potássio foi utilizada para determinar etanol em amostras de uísques apreendidos pela Polícia Federal. Foi possível determinar etanol na faixa de 0% a 60%(v/v) utilizando canal de cor cinza para a faixa de concentração de 0% a 20%(v/v) com R 2 =0,993, com um limite de detecção 0,86% de e limite de quantificação de 1,44% e o canal de cor amarelo para a faixa de concentração de 20% a 60%(v/v) com R 2 =0,998. Foi possível determinar o teor de etanol em 66 amostras de uísques apreendidos. Onde 53 amostras foram discriminadas como falsificadas, com 13 sendo classificadas como autênticas com base no teor de etanol.

Although the growth of native corneal epithelial cells over the anterior surface of an artificial corneal implant is desired, the growth of these cells on the interface located between the implant and the stromal layer of the host eye tissue (i.e. epithelial cell downgrowth) poses a significant problem to be overcome in developing a suitable implant. In this study the growth factor surface modification of a polymer substrate was examined as a means of inhibiting the proliferation of corneal epithelial cells while promoting corneal stromal cell growth. Two separate studies were conducted in which transforming growth factor-beta1 (TGF-beta1) and transforming growth factor-beta2 (TGF-beta2) respectively, were immobilized via a bifunctional poly (ethylene glycol) (PEG) spacer, MW 3400, to poly(dimethyl siloxane) surfaces (PDMS) that had been aminated by the plasma polymerization of allylamine. The modified surfaces were chemically and biologically characterized. The effect of the surface modification with TGF-beta1 and TGF-beta2 respectively, on interactions with corneal epithelial and corneal stromal cells was examined using in vitro cell culture. (Abstract shortened by UMI.)

Hydrophilic poly(2-hydroxyethyl methacrylate), PHEMA, and hydrophobic poly(dimethyl siloxane), PDMS, segments containing copolymers have been widely used as a biomaterial. These amphiphilic copolymers also used as an emulsifying agent in polymer solutions and compatibilizer in polymer blends. In this case, solution polymerizations of HEMA by radiation, ATRP and RAFT methods were studied. The thermal degradation mechanism of PHEMA, which was prepared in aqueous solution by gamma radiation technique, was studied in detail. The DSC, TGA and Mass Spectroscopy analyses revealed that the degradation is linkage and depolymerization with a combination of monomer fragmentation. The ATRP of HEMA was performed with ethyl-2-bromoisobutyrate (EBriB) initiator and CuCl/bipyridine catalyst in MEK/1-propanol solvent mixture. Cu(II) complexes and PHEMA obtained via ATRP were characterized by UV-vis, FTIR and 1H-NMR analysis. The RAFT polymerization of HEMA with different [RAFT]/[AIBN] ratios were also investigated in three solvents (methyl ethylketone, ethyl acetate and toluene). The controlled polymerization of HEMA with the ratio of [RAFT]/ [AIBN]=18 at 80 oC in MEK and ethyl acetate, shows the first-order kinetic up to the nearly 40 % conversion Macroazoinitiator PDMS-MAI was synthesized from bifunctional PDMS and then copolymerized with MMA, EMA, HEMA and TMS-HEMA monomers Different characterization methods such as FTIR, 1H-NMR, solid state NMR, GPC, XPS, SEM, DSC, etc. have been used for the characterization of block copolymers. P(DMS-b-TMSHEMA) was converted to the P(DMS-b-HEMA) block copolymer by deprotection of TMS groups. The phase separated morphology was observed for the P(DMS-b-HEMA) copolymer, which was different from P(DMS-b-MMA) and P(DMS-b-EMA) copolymers.

In vitro cell culture is an essential part of many cell and tissue engineering approaches. In particular, monolayer culture of mammalian cells is a key tool for applications such as cell therapy. Novel bioreactors like the Cellerator(TM) allow for expansion of cell populations on mechanically stimulated surfaces coated with proteins. This thesis constitutes a preliminary study which focused on cell-matrix interactions in the absence of stretch. The aim was to establish standard protocols for protein coating on poly (dimethyl siloxane) (PDMS) and for measuring cell proliferation. Specifically, the proliferation of rat pulmonary artery vascular smooth muscle (PAC1) cells on type I collagen and soluble fibronectin was studied. Growth curves were obtained and the doubling time for subconfluent cultures was computed. Although cell-matrix interactions do not enhance proliferation of PAC1 cells, it was found that a preliminary sulphuric acid treatment is necessary to yield a well-behaved culture.

Synthèses et caractérisation des oligomères; synthèse de copolymères à blocs poly(sulfone-b-siloxane) à partir de la réaction phenol-epoxy; synthèse des mêmes copolymères par hydrosilylation; étude sur modèles de la réaction d'hydrosilylation et caractérisation des réactions secondaires.

Polysiloxanes represent a unique class of synthetic polymers, employing a completely inorganic backbone structure comprised of repeating –(Si–O)n– 'siloxane' main chain linkages. This results in an assortment of diverse properties exclusive to the siloxane bond that clearly distinguish them from the –(C–C)n– backbone of purely organic polymers. Previous work has elucidated a methodology for fabricating flexible and elastic crosslinked poly(dimethyl siloxane) (PDMS) constructs with high Mc through a simultaneous crosslinking and chain-extension methodology. However, these constructs suffer the poor mechanical properties typical of lower molecular weight crosslinked siloxanes (e.g. modulus, tear strength, and strain at break). Filled PDMS networks represent another important class of elastomers in which fillers, namely silica and siloxane-based fillers, impart improved mechanical properties to otherwise weak PDMS networks. This work demonstrates that proper silicon-based reinforcing agent selection (e.g. siloxane-based MQ copolymer nanoparticles) and incorporation provides a synergistic enhancement to mechanical properties, whilst maintaining a low viscosity liquid composition, at high loading content, without the use of co-solvents or heating. Rheological analysis evaluates the viscosity while photorheology and photocalorimetry measurements evaluate rate and extent of curing of the various MQ-loaded formulations, demonstrating theoretical printability up to 40 wt% MQ copolymer nanoparticle incorporation. Dynamic mechanical analysis (DMA) and tensile testing evaluated thermomechanical and mechanical properties of the cured nanocomposites as a function of MQ loading content, demonstrating a 3-fold increase in ultimate stress at 50 wt% MQ copolymer nanoparticle incorporation. VP AM of the 40 wt% MQ-loaded, photo-active PDMS formulation demonstrates facile amenability of photo-active PDMS formulations with high MQ-loading content to 3D printing processes with promising results. PDMS polyureas represent an important class of elastomers with unique properties derived from the synergy between the nonpolar nature, unusual flexibility, and low glass transition temperature (Tg) afforded by the backbone siloxane linkages (-Si-O)n- of PDMS and the exceptional hydrogen bond ordering and strength evoked by the bidentate hydrogen bonding of urea. The work herein presents an improved melt polycondensation synthetic methodology, which strategically harnesses the spontaneous pyrolytic degradation of urea to afford a series of PDMS polyureas via reactions at high temperatures in the presence of telechelic amine-terminated oligomeric poly(dimethyl siloxane) (PDMS1.6k-NH2) and optional 1,3-bis(3-aminopropyl)tetramethyldisiloxane (BATS) chain extender. This melt polycondensation approach uniquely circumvents the accustomed prerequisite of isocyanate monomer, solvent, and metal catalysts to afford isocyanate-free PDMS polyureas using bio-derived urea with the only reaction byproduct being ammonia, a fundamental raw ingredient for agricultural and industrial products. As professed above, reinforcement of polysiloxane materials is ascertained via the incorporation of reinforcing fillers or nanoparticles (typically fumed silica) or blocky or segmented development of polymer chains eliciting microphase separation, in order to cajole the elongation potential of polysiloxanes. Herein, a facile approach is detailed towards the synergistic fortification of PDMS-based materials through a collaborative effort between both primary methods of polysiloxane reinforcement. A novel one-pot methodology towards the facile, in situ incorporation of siloxane-based MQ copolymer nanoparticles into segmented PDMS polyureas to afford MQ-loaded thermoplastic and thermoplastic elastomer PDMS polyureas is detailed. The isocyanate-free melt polycondensation achieves visible melt dispersibility of MQ copolymer nanoparticles (good optical clarity) and affords segmented PDMS polyureas while in the presence of MQ nanoparticles, up to 40 wt% MQ, avoiding post-polymerization solvent based mixing, the only other reported alternative. Incorporation of MQ copolymer nanoparticles into segmented PDMS polyureas provides significant enhancements to modulus and ultimate stress properties: results resemble traditional filler effects and are contrary to previous studies and works discussed in Chapter 2 implementing MQ copolymer nanoparticles into chemically-crosslinked PDMS networks. In situ MQ-loaded, isocyanate-free, segmented PDMS polyureas remain compression moldable, affording transparent, free-standing films.
Master of Science
Polysiloxanes, also referred to as 'silicones' encompass a unique and important class of polymers harboring an inorganic backbone. Polysiloxanes, especially poly(dimethyl siloxane) (PDMS) the flagship polymer of the family, observe widespread utilization throughout industry and academia thanks to a plethora of desirable properties such as their incredible elongation potential, stability to irradiation, and facile chemical tunability. A major complication with the utilization of polysiloxanes for mechanical purposes is their poor resistance to defect propagation and material failure. As a result polysiloxane materials ubiquitously observe reinforcement in some fashion: reinforcement is achieved either through the physical or chemical incorporation of a reinforcing agent, such as fumed silica, or through the implementation of a chemical functionality that facilitates reinforcement via phase separation and strong associative properties, such as hydrogen bonding. This research tackles polysiloxane reinforcement via both of these strategies. Facile chemical modification permits the construction PDMS polymer chains that incorporate hydrogen bonding motifs, which phase separate to afford hydrogen bond-reinforced phases that instill vast improvements to elastic behavior, mechanical and elongation properties, and upper-use temperature. Novel nanocomposite formulation through the incorporation of MQ nanoparticles (which observe widespread usage in cosmetics) facilitate further routes toward improved mechanical and elongation properties. Furthermore, with growing interest in additive manufacturing strategies, which permit the construction of complex geometries via an additive approach (as opposed to conventional manufacturing processes, which require subtractive approaches and are limited in geometric complexity), great interest lies in the capability to additively manufacture polysiloxane-based materials. This work also illustrates the development of an MQ-reinforced polysiloxane system that is amenable to conventional vat photopolymerization additive manufacturing: chemical modification of PDMS polymer chains permits the installation of UV-activatable crosslinking motifs, allowing solid geometries to be constructed from a liquid precursor formulation.

Poly(dimethylsiloxan) (PDMS) ist ein wichtiges Polymer, das zunehmend in der Mikroelektronik aufgrund seiner hervorragenden Elastizität und thermischen Stabilität Verwendung findet. Ein limitierender Faktor für den Einsatz von PDMS ist aufgrund des Fehlens von reaktiven Gruppen und der niedrigen freien Oberflächenenergie seine geringe Adhäsion zu anderen Materialien. Zur Erhöhung der Adhäsion ist deshalb die Einführung von polaren, funktionellen Gruppen notwendig. Hier lag die Motivation der vorliegenden Arbeit, die sich eine gezielte Funktionalisierung von PDMS-Oberflächen als Aufgabe gesetzt hatte. Im ersten Teil der Arbeit wurde eine Verbesserung der Adhäsion zu einem fotostrukturierbaren Epoxidharz mittels der Sauerstoff- und Ammoniakplasmabehandlung angestrebt. In beiden Fällen führte die Plasmabehandlung zu der Einführung von unterschiedlichsten funktionellen Gruppen auf die Oberfläche und zu einer Verbesserung des Benetzungsverhaltens gegenüber Wasser. Zudem wurden Haftfestigkeiten erzielt, die um ein Vielfaches höher waren als jene zwischen Epoxidharz und einer unbehandelten PDMS-Oberfläche. Jedoch waren die hydrophilen Eigenschaften nach der Plasmabehandlung während der Lagerung an Luft zeitlich begrenzt, die PDMS-Oberfläche kehrt innerhalb kurzer Zeit in den einst hydrophoben Ausgangszustand zurück. Der Alterungsvorgang wird als „Hydrophobic Recovery“ bezeichnet und ist bei PDMS-Oberflächen, die höheren Plasmaleistungen und Behandlungszeiten ausgesetzt wurden, besonders auffällig. Die Vermeidung dieser Problematik war der Ausgangspunkt für den zweiten Teil der Arbeit. Auf der Grundlage der über die Plasmabehandlungen erzeugten funktionellen Gruppen wurden neue Konzepte für eine kovalente Anbindung von verschiedenen funktionellen Homo- und Copolymeren über die „Grafting to“-Technik entwickelt. Neben der Erhöhung der Adhäsion zu dem Epoxidharz war es möglich, das Benetzungsverhalten gegenüber Wasser durch die Unterbindung der „Hydrophobic Recovery“ zu stabilisieren. Des Weiteren gelang es, durch die Wahl der funktionellen Polymere, die PDMS-Oberfläche gezielt mit gewünschten Eigenschaften auszustatten. Somit ist der Einsatz der polymermodifizierten Oberflächen, außer in der Mikroelektronik, auch auf andere Anwendungen, wie der Biomedizin, der Mikrofluidik oder der Softlithografie übertragbar, in denen eine beständige, definierte Oberflächenfunktionalisierung ein wichtiges Kriterium darstellt.

Poly(dimethylsiloxan) (PDMS) ist ein wichtiges Polymer, das zunehmend in der Mikroelektronik aufgrund seiner hervorragenden Elastizität und thermischen Stabilität Verwendung findet. Ein limitierender Faktor für den Einsatz von PDMS ist aufgrund des Fehlens von reaktiven Gruppen und der niedrigen freien Oberflächenenergie seine geringe Adhäsion zu anderen Materialien. Zur Erhöhung der Adhäsion ist deshalb die Einführung von polaren, funktionellen Gruppen notwendig. Hier lag die Motivation der vorliegenden Arbeit, die sich eine gezielte Funktionalisierung von PDMS-Oberflächen als Aufgabe gesetzt hatte. Im ersten Teil der Arbeit wurde eine Verbesserung der Adhäsion zu einem fotostrukturierbaren Epoxidharz mittels der Sauerstoff- und Ammoniakplasmabehandlung angestrebt. In beiden Fällen führte die Plasmabehandlung zu der Einführung von unterschiedlichsten funktionellen Gruppen auf die Oberfläche und zu einer Verbesserung des Benetzungsverhaltens gegenüber Wasser. Zudem wurden Haftfestigkeiten erzielt, die um ein Vielfaches höher waren als jene zwischen Epoxidharz und einer unbehandelten PDMS-Oberfläche. Jedoch waren die hydrophilen Eigenschaften nach der Plasmabehandlung während der Lagerung an Luft zeitlich begrenzt, die PDMS-Oberfläche kehrt innerhalb kurzer Zeit in den einst hydrophoben Ausgangszustand zurück. Der Alterungsvorgang wird als „Hydrophobic Recovery“ bezeichnet und ist bei PDMS-Oberflächen, die höheren Plasmaleistungen und Behandlungszeiten ausgesetzt wurden, besonders auffällig. Die Vermeidung dieser Problematik war der Ausgangspunkt für den zweiten Teil der Arbeit. Auf der Grundlage der über die Plasmabehandlungen erzeugten funktionellen Gruppen wurden neue Konzepte für eine kovalente Anbindung von verschiedenen funktionellen Homo- und Copolymeren über die „Grafting to“-Technik entwickelt. Neben der Erhöhung der Adhäsion zu dem Epoxidharz war es möglich, das Benetzungsverhalten gegenüber Wasser durch die Unterbindung der „Hydrophobic Recovery“ zu stabilisieren. Des Weiteren gelang es, durch die Wahl der funktionellen Polymere, die PDMS-Oberfläche gezielt mit gewünschten Eigenschaften auszustatten. Somit ist der Einsatz der polymermodifizierten Oberflächen, außer in der Mikroelektronik, auch auf andere Anwendungen, wie der Biomedizin, der Mikrofluidik oder der Softlithografie übertragbar, in denen eine beständige, definierte Oberflächenfunktionalisierung ein wichtiges Kriterium darstellt.

Materiais dielétricos flexíveis e filmogênicos são essências para a produção de diversos dispositivos tecnológicos, tais como Organic Light Emiting Diodes (OLED), Transistores de Efeito de Campo (FET do Inglês Field Emission Transistor) ou fotovoltaicos orgânicos (OPV do Inglês Organic Photovoltaics). Dentro deste contexto, é importante salientar o esforço de desenvolver rotas sintéticas mais sustentáveis baseadas em matérias-primas e processos mais amigáveis ao meio ambiente. No Grupo de Química de Materiais Híbridos e Inorgânicos (GQMATHI) há mais de dez anos se pesquisa rotas sintéticas de preparação de oligômeros e polímeros de uretanas usando CO2 como matéria-prima. Assim, são sintetizados os materiais classificados como polihidroxi-uretânicos, que são obtidos a partir do monômero bis-ciclocarbonato de polidimetilsiloxano (CCPDMS) mediante a reação de polimerização por abertura de anel (ROP - do inglês Ring Oppening Polymerization). O monômero é obtido pela reação de cicloadição de CO2 no seu respectivo epóxido: poli(dimetil-siloxano) diglicidil éter (PDMS). Neste projeto os materiais hidroxi-uretânicos foram sintetizados, utilizando tanto o CCPDMS como monômero precursor da reação, como o ciclocarbonato de bisfenol A diglicidil éter (CCDGEBA). O oligômero formado foi ensaiado em diferentes proporções destes dois ciclocarbonatos na reação frente à uma diamina (5-Amino-1,3,3-trimetilciclohexanometilamina ,IFDA). Utilizou-se como grupo terminador de cadeia o 3-aminopropiltrietóxissilano (APTS). Os ciclocarbonatos foram caracterizados por espectroscopia vibracional (FTIR) e de ressonância magnética nuclear (RMN) de 13C e 1H. Na espectroscopia vibracional a formação do grupamento ciclocarbonato foi obtida pela presença da banda de carbonila em 1790 cm-1 , enquanto na RMN os sinais do duplo dubleto próximo de 4,5 ppm (1H) e o pico em 154 ppm (13C) foram interpretados como sinais carcaterísticos do grupo ciclocarbonato. O material oligomérico sintetizado a partir dos ciclocarbonatos foi caracterizado por análise termogravimétrica (TGA), calorimetria diferencial de varredura (DSC), análise dinâmico-mecânica (DMA) bem como filmes dos mesmos foram preparados via spin coating. Os filmes foram caracterizados eletricamente por medidas de espectroscopia de impedância, visando avaliar a possibilidade do material ser utilizado como camada dielétrica em transístores orgânicos do tipo FET. Visando um melhor desempenho do material hidroxi-uretânico nesta aplicação o dióxido de titânio (constante dielétrica (ε) ≈ 100) foi introduzido na matriz polimérica. Assim sendo, a introdução desta cerâmica classificará o material formado como um material compósito do tipo híbrido inorgânico-orgânico. Este híbrido também foi caracterizado por espectroscopia de impedância revelando um aumento da constante dielétrica, porém um aumento da perda dielétrica também foi observada para o híbrido.
Flexible and film-forming dielectric materials are essential for the production of various technological devices, such as Organic Light Emitting Diodes (OLED), Field Effect Transistors (FETs) or organic photovoltaics (OPVs). Within this context, it is important to highlight the effort to develop more sustainable synthetic routes based on raw materials and more environmentally friendly processes. In the Group of Chemistry of Hybrid and Inorganic Materials (GQMATHI) more than ten years ago, synthetic routes for preparation of oligomers and polymers of urethanes using CO2 as raw material have been investigated. Thus, materials classified as polyhydroxy urethanes, which are obtained from the bis-cyclocarbonate monomer of polydimethylsiloxane (CCPDMS) are synthesized by the Ring Oppening Polymerization (ROP) reaction. The monomer is obtained by the cycloaddition reaction of CO2 in its respective epoxide: poly (dimethylsiloxane) diglycidyl ether (PDMS). In this project the hydroxy urethane materials were synthesized, using two different types of precursor monomer : the CCPDMS and bisphenol A diglycidyl ether cyclocarbonate (CCDGEBA). The oligomer formed was tested in different ratios of these two cyclocarbonates in the reaction against a diamine (5-Amino-1,3,3-trimethylcyclohexanemethylamine (IFDA)). The aminopropyltriethoxysilane (APTS) was used as the chain terminator group. After the synthesis of the cyclocarbonates, characterizations were made by vibrational spectroscopy (IR) and nuclear magnetic resonance (NMR) of 13C and 1H. The successful formation of the cyclocarbonate was confirmed by the 1790 cm-1 peak in the vibrational spectroscum as well as by the dublet near 4.5 ppm (1H NMR) and the singlet at 154 ppm (13 C NMR). The oligomeric hydroxyurethane synthesized from the cyclocarbonates reaction with IFDA and APTS was characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic-mechanical analysis (DMA) and films were prepared by spin coating. The electrical characterization of the films was made by impedance spectroscopy, aiming to evaluate its application on organic FET´s as adielectric layer . In order to improve the performance of the hydroxy urethane material for this application, titanium dioxide (dielectric constant (ε) ≈ 100) was incorporated into the oligomer matrix, thus an hybrid nanocomposite material was formed. The impedance chacacterization of the hybrid was performed showing higher dielectric constant for this new material, although observed a higher dielectric loss, 9 vs 0,2 ,respectively for the hydroxyurethane and the hybrid.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
In this work, poly coatings were obtained (dimethyl siloxane) with silver nanoparticles (PDMS / AgNPs), produced by the method of solution blow spraying (SBSp), a technique of adapting Solution Blow Spinning (SBS), with potential for application in packaging and equipment coatings in the food industry. AgNPs synthesized by Turkevich method were deposited on the PDMS film SBSp technique and tested antimicrobial activity against microorganisms S. aureus and E. coli (ATCC). The results of dynamic light scattering (DLS) showed that AgNPs had an average size of 170,5 nm. In addition, these nanoparticles show antimicrobial activity, in accordance with the disk diffusion test, and were considered for nontoxic toxicity tests against Artemia salina. The AgNPs were deposited on the PDMS films at various intervals cure this resin. Scanning electron microscopy (SEM) allowed the observation that the films form uniform coatings with a thickness of 1,62 ± 0,2μm and the particles are evenly distributed over the surface of the film (SEM-EDS) with concentrations varying according to the time and number of depositions of AgNPs. These results were also corroborated by atomic force microscopy (AFM) and atomic emission spectrometry with inductively coupled plasma (ICP / AES). When the application of AgNPs was performed at the end or after the course of ¾ PDMS curing time, there was a greater reduction in cell adhesion and biofilm formation uniespécie for S. aureus and E. coli (ATCC). This reduction has also been improved when multiple applications AgNPs were made. Once all coatings showed antimicrobial activity, their use in food industry can be considered promising.
Neste trabalho, foram obtidos revestimentos de poli(dimetil siloxano) com nanopartículas de prata (PDMS/AgNPs), produzidos pelo método de solution blow spraying (SBSp), uma adaptação da técnica de Solution Blow Spinning (SBS), com potencial para aplicação em embalagens e revestimentos de equipamentos na indústria de alimentos. AgNPs, sintetizadas pelo método de Turkevich, foram depositadas sobre filmes de PDMS pela técnica de SBSp e a atividade antimicrobiana testada contra os micro-organismos S. aureus e E. coli (ATCC). Os resultados de espalhamento dinâmico de luz (DLS) mostraram que as AgNPs tiveram tamanho médio de 170,5 nm. Além disso, essas nanopartículas apresentaram atividade antimicrobiana, de acordo com o teste de disco de difusão, e foram consideradas atóxicas pelo teste de toxicidade frente a Artemia salina. As AgNPs foram depositadas sobre os filmes de PDMS em vários intervalos de cura dessa resina. Análises por microscopia eletrônica de varredura (MEV) permitiram observar que os filmes formam revestimentos uniformes com espessura de 1,62 ± 0,2μm e que as partículas estão uniformemente distribuídas pela superfície do filme (MEV-EDS) com concentrações variando de acordo com o tempo e número de deposições das AgNPs. Estes resultados também foram corroborados por microscopia de força atômica (AFM) e espectrometria de emissão atômica com plasma acoplado indutivamente (ICP/AES). Quando a aplicação das AgNPs foi realizada no final ou após decorrer ¾ do tempo de cura do PDMS, houve uma redução mais significativa na adesão celular e formação de biofilme uniespécie para S. aureus e E. coli (ATCC). Essa redução também foi melhorada quando múltiplas aplicações de AgNPs foram feitas. Uma vez que todos os revestimentos apresentaram atividade antimicrobiana, sua utilização na indústria de alimentos pode ser considerada promissora.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.
Source: Dissertation Abstracts International, Volume: 68-06, Section: B, page: 4065. Adviser: Nancy R. Sottos. Includes bibliographical references (leaves 98-103) Available on microfilm from Pro Quest Information and Learning.

碩士
長庚大學
化工與材料工程研究所
92
The objective of this study was to investigating poly(dimethyl siloxane) membrane and organic solvents interaction using low temperature differential scanning calorimetry(DSC). The organic solvents used include water, cyclohexane, benzene, toluene and m-xylene. The diffusion coeifficients of organic solvents of free state and bound state were calculated vapor and solvent sorption kinetics through gravimetic method. The enthalpy values of solvents and PDMS membranes were determined and the solvent contents of free state were measured by comparing their enthalpy with pure solvent. The maxumim bound amount of solvent in PDMS was in the order cyclohexane > m-xylene > toluene > benzene, as in the reverse of difference in the solubility parameter between solvents and PDMS. Therefore it indicated that solvent content in PDMS was related to its solubility parameter. Its was found that diffusion coeifficient of the free state solvent was one magnitude higher than that in the bound state and the diffusivity was in the order toluene > cyclohexane > benzene > m-xylene. The solvent diffusivity in PDMS depended on the solvent nature, solubility and the penetrant state.

碩士
長庚大學
化工與材料工程研究所
94
Greenhouse effect has become a crucial environmental issue due to the global warming phenomena around the world. Searching for separation and recovery methodology is one of the key components to solve this long-term problem. This research studies the use of polydimethyl siloxane (PDMS) membrane with or without filler (nanoparticles and zeolite) to separate greenhouse gases (CO2 and SF6) from N2.The results show that the nitrogen and SF6 permeabilities decreased with gas pressure while CO2 permeability increased with upstream pressure. PDMS-fumed silica (addition content 15Wt.%) nan- -ocomposite membranes showed higher permeabilities for N2 and SF6 gases, but lower CO2 permeability. The selectivity for SF6/N2 or CO2/N2 gas pair was slightly reduced compared with the PDMS membrane. PDMS-Zeolite (Type-Y) (addition content 12Wt.%) composite membranes showed reduced the CO2 permeabilities.The N2 and SF6 permeability was similar to that of the pure PDMS. The SF6/N2 or CO2/N2 selectivity was similar to that of the pure PDMS. PDMS-Zeolite (ZSM-5) (addition content 12-40Wt.%) composite membranes showed reduced the N2 and increased CO2 permeabilities, but had no significant effect SF6 on the permeability. The selectivity increased with zeolite content for CO2/N2.The SF6/N2 selectivity was similar to that of the pure PDMS.All PDMS-ZSM experimental data will simulation and analysis with Maxwell model .

Im Rahmen der vorliegenden Arbeit werden die Synthese und Charakterisierung eines thermisch-kontrollierten und eines photochemisch-kontrollierten reversiblen Polymersystems vorgestellt. Weiterhin werden Poly(dimethyl)siloxan-Oberflächen mit Amino-, Isocyanat-, Furan-, Maleimid- und Cumarin-Gruppen funktionalisiert. Hierbei werden sowohl bekannte als auch neuartige Wege der Oberflächenmodifizierung vergleichend untersucht und bewertet. Ausgehend von den hergestellten Cumarin-funktionalisierten Poly(dimethyl)siloxan-Oberflächen wird eine Anbindung des synthetisierten photochemisch-kontrollierten reversiblen Polymersystems an diese Oberflächen untersucht. Des Weiteren wird die Anbindung des synthetisierten thermisch kontrollierten reversiblen Polymersystems sowohl an den hergestellten Maleimid- als auch an den Furan-funktionalisierten Poly(dimethyl)siloxan-Oberflächen analysiert. Basierend auf den vorgestellten Cumarin-Funktionalisierungen werden photoaktive Oberflächen beschrieben und mittels ATR-IR-spektroskopischer und UV/Vis-spektroskopischer Methoden analysiert.:Inhaltsverzeichnis 6 Abkürzungsverzeichnis 10 Kapitel I Einleitung und Zielstellung 13 I.I Poly(dimethyl)siloxan 13 I.II Funktionalisierung von Oberflächen 15 I.III Reversible Polymere an Oberflächen 18 I.IV Photoaktive Oberflächen 20 Kapitel II Sauerstoffplasma-Modifizierung 21 II.I Vorbetrachtung 21 II.I. a) Plasmen – Definition und Charakterisierung 21 II.I. b) Technisch angewandte Plasmaprozesse 24 II.II Hintergrund und Motivation Sauerstoffplasma-modifizierter PDMS-Oberflächen 27 II.II. a) ATR-IR-spektroskopische Charakterisierung von Sauerstoffplasma-modifizierten PDMS-Oberflächen 28 II.II. b) Rasterkraftmikroskopische Charakterisierung von Sauerstoffplasma-modifizierten PDMS-Oberflächen 34 II.II. c) Untersuchungen zum Quellverhalten von PDMS 35 II.III Zusammenfassung 38 II.IV Experimenteller Teil 39 II.IV. a) Herstellung von Substraten aus Poly(dimethyl)siloxan 39 II.IV. b) Sauerstoffplasma-Modifikation von Poly(dimethyl)siloxan 39 Kapitel III Amino-funktionalisierte Oberflächen 40 III.I Hintergrund und Motivation Amino-funktionalisierter Oberflächen 40 III.I. a) Amino-Funktionalisierung mittels 3 Aminopropyltriethoxysilan (APTES) 41 III.I. b) Amino-Funktionalisierung nach Balachander & Sukenik 43 III.I. c) Amino-Funktionalisierung mittels Phenylendiisocyanat (PDI) 45 III.II Kontaktwinkelanalyse von unterschiedlichen Amino-Beschichtungen 48 III.III Zusammenfassung 49 III.IV Experimenteller Teil 50 III.IV. a) Amino-Funktionalisierung von PDMS-Substraten mittels APTES 50 III.IV. b) Amino-Funktionalisierung von PDMS-Substraten nach Balachander & Sukenik 50 III.IV. c) Amino-Funktionalisierung von PDMS-Substraten mittels PDI 51 Kapitel IV Maleimid-funktionalisierte Oberflächen 52 IV.I Hintergrund und Motivation Maleimid-funktionalisierter Oberflächen 52 IV.II Synthese Maleimid-funktionalisierter PDMS-Oberflächen 53 IV.II. a) Syntheseroute via Maleinsäureanhydrid (MSA-Route) 53 IV.II. b) Trichlorosilyl-funktionalisierte Maleimid-Derivate 56 IV.III Experimenteller Teil 59 IV.III. a) Synthese eines furangeschützten Maleimids 59 IV.III. b) Synthese eines furangeschützten Undec-10-enyl-1-maleimids (13) 59 IV.III. c) Synthese eines furangeschützten 11-Trichlorosilyl-undecyl-1-maleimids (14) 60 IV.III. d) Maleimid-Funktionalisierung von PDMS-Substraten mittels MSA 61 IV.III. e) Maleimid-Funktionalisierung von PDMS-Substraten mittels trichlorosilyl-funktionalisierter Maleimid-Derivate 62 Kapitel V Furan-funktionalisierte Oberflächen 63 V.I Hintergrund und Motivation Furan-funktionalisierter Oberflächen 63 V.II Herstellung Furan-funktionalisierter PDMS-Oberflächen 65 V.II. a) Trichlorosilyl-funktionalisierte Furan-Derivate an Hydroxyl-Oberflächen 65 V.II. b) Furfural an Amino-Oberflächen 67 V.II. c) Furfurylalkohol an Isocyanat-Oberflächen 69 V.III Zusammenfassung 71 V.IV Experimenteller Teil 72 V.IV. a) Synthese von Undec-10-enyl-furan-2-carboxylat (15) vgl. 72 V.IV. b) Synthese von 11-(Trichlorosilyl)undecyl- furan-2-carboxylat (16) vgl. 72 V.IV. c) Furan-Funktionalisierung mittels 11 (Trichlorosilyl)undecyl furan 2 carboxylat (16) 73 V.IV. d) Furan-Funktionalisierung mittels Furfural nach 74 V.IV. e) Furan-Funktionalisierung mittels Furfurylalkohol vgl. 74 Kapitel VI Reversible Polymere 75 VI.I Hintergrund und Motivation reversibler Polymere 75 VI.II Thermisch-kontrollierte reversible Polymerisation (DIELS-ALDER-Reaktion) 77 VI.II. a) Hintergrund thermisch-kontrollierter reversibler Polymerisationen 77 VI.II. b) DIELS-ALDER-AB-Monomer mit flexiblem Spacer 80 VI.II. c) Charakterisierung der thermisch-kontrollierten Polymerisation 83 VI.III Zusammenfassung 96 VI.IV Photochemisch-kontrollierte reversible Polymerisation 97 VI.IV. a) Hintergrund photochemisch-kontrollierter reversibler Polymerisationen 97 VI.IV. b) Synthese geeigneter Biscumarine 101 VI.V Experimenteller Teil 108 VI.V. a) Thermisch-kontrollierte reversible Polymerisationen 108 VI.V. b) Photochemisch-kontrollierte reversible Polymerisationen 114 Kapitel VII Reversible Polymere an Oberflächen 117 VII.I Anbinden von DIELS-ALDER-AB-Polymeren an Maleimid- und Furan-Oberflächen 117 VII.I. a) ATR-IR-spektroskopische Charakterisierung 119 VII.II Zusammenfassung 121 VII.III Anbinden von Biscumarinen an Cumarin-Oberflächen 122 VII.III. a) ATR-IR-spektroskopische Charakterisierung 123 VII.IV Zusammenfassung 125 VII.V Experimenteller Teil 126 VII.V. a) Anbinden von DIELS-ALDER-AB-Polymeren an Maleimid-Oberflächen 126 VII.V. b) Anbinden von DIELS-ALDER-AB-Polymeren an Furan-Oberflächen 126 VII.V. c) Anbinden von Biscumarin an Cumarin-Oberflächen 126 Kapitel VIII Photoaktive Oberflächen 127 VIII.I Hintergrund und Motivation Cumarin-funktionalisierter Oberflächen 127 VIII.II Synthese Cumarin-funktionalisierter PDMS-Oberflächen 129 VIII.II. a) Funktionalisierung von PDMS-Oberflächen mit Cumarin-Gruppen 129 VIII.II. b) Allgemeine Bemerkung zur Wahl des Lösungsmittels 130 VIII.II. c) Photochemie von Cumarin-funktionalisierten PDMS-Oberflächen 131 VIII.II. d) ATR-IR-spektroskopische Charakterisierung photoaktiver Cumarin-Beschichtungen 132 VIII.III UV/Vis-spektroskopische Charakterisierung photoaktiver Cumarin-Beschichtungen 137 VIII.III. a) Belichtung mit UVA-Strahlung 137 VIII.III. b) Belichtung mit UVC-Strahlung 140 VIII.IV Zusammenfassung 142 VIII.V Experimenteller Teil 144 VIII.V. a) Funktionalisierung von PDMS-Substraten mit Isocyanat 144 VIII.V. b) Funktionalisierung von PDMS-Substraten mit Cumarin 144 VIII.V. c) Photochemisch-kontrollierte Modifikation von PDMS-Substraten mit Cumarin-Beschichtung 144 Kapitel IX Zusammenfassung und Ausblick 145 Kapitel X Anhang 150 X.I Messmethoden 150 X.I. a) ATR-IR-Spektroskopie 150 X.I. b) UV/Vis-Spektroskopie 150 X.I. c) Kontaktwinkelanalyse 151 X.I. d) Rasterkraftmikroskopie (AFM) 151 X.I. e) NMR-Spektroskopie 152 X.I. f) Größenausschluss-Chromatographie (SEC) 152 X.I. g) Thermoanalyse (TA) 152 X.I. h) Thermogravimetrie (TGA) 153 X.I. i) Dynamische Differenzkalorimetrie (DSC) 153 X.II Trocknen von Lösungsmitteln , 153 Kapitel XI Literatur 154 Selbstständigkeitserklärung 161 Lebenslauf 162 Danksagung 163

Adoptive cell transfer (ACT) has garnered significant interest in recent years within the medical field due to its potential in providing an effective form of personalized medicine for patients suffering from a wide range of chronic illnesses, including but not limited to cancer. By leveraging the patient’s own cells as the therapeutic agent, concerns over patient compatibility and adverse reactions are significantly reduced. Central to this therapy is the ability to optimize cell quantity and cell activation in order to produce a more robust infusion to the patient. This thesis focuses on two main aspects. The first is the materials synthesis and development of a novel platform for the ex vivo expansion of human T cells for ACT, while the second aims to elucidate the underlying structural mechanics of this platform. This platform, which consists of an electrospun mesh of micron and sub-micron diameter poly (dimethyl siloxane)-based fibers, aims to maintain the high surface-area to volume ratio characteristic of the current clinical gold standard. This also simultaneously allows for effective leveraging of T cell mechanosensing, a phenomenon previously discovered by our lab that is the ability of a human T cell to respond differently to surface mechanical cues. By modulating the concentration of poly (ε-caprolactone) in these fibers, a biocompatible polymer, the mesh mechanical rigidity was varied: this effectively allowed for the leverage of T cell mechanosensing by maintaining a low and tunable Young’s modulus throughout. Additionally, safety concerns involving transfusion of the expansion platform into the patient were addressed by having a single continuous substrate instead of an array of disjoint ferromagnetic beads. Our results thus far indicate that this soft mesh platform can produce upwards of 5.6-12.5 times more T cells in healthy patients than the clinical gold standard while maintaining comparable levels of cellular activation and phenotypic distributions as measured through IFNγ secretion and expression of surface proteins CD107b, CD45RO, and CCR7, respectively. Additionally, this platform demonstrates the ability to produce improved expansion of exhausted (PD-1high) T cells from CLL patients compared to the clinical gold standard across all analyzed Rai stages. Finally, experiments have shown our platform to be scalable to produce clinically relevant levels of cells (> 50 million) from a given starting population, thus indicating its potential in adaptation in larger scale in vitro systems. The currently demonstrated capabilities of our mesh platform thus hold significant promise in the clinical development and adoption of ACT, as well as the development of larger scale in vitro systems. In order to elucidate the underlying structural mechanics of our platform, quantitative AFM studies have indicated a force-dependency in rigidity measurement, thus indicating that standard Hertzian contact models and their derivatives (DMT, Sneddon, etc.), may not be ideal in calculating the rigidity of this material. In order to better model the effective Young’s modulus (E_eff) of the mesh and account for cantilever beam-bending type mechanical deformation, a modification of Euler-Bernoulli theory was established. This mathematical model was subsequently used to correlate fiber geometry parameters to bending stiffness, thus allowing for us to estimate E_eff for a range of meshes. Subsequent T cell expansions and comparison of data to previous expansions on planar surfaces provided verification of our model.

碩士
國立中正大學
化學工程研究所
102
The purpose of the experiment is to enhance the hydrophilicity of the roller material for contact printing. First, the crosslinking agent was reacted with the hydroxyl terminated Poly (dimethylsiloxane) (PDMS) via Sol-gel reaction, to form crosslinked PDMS. This crosslinked PDMS was then cutted into sheets, and reacted with diisocyanate. Addition reaction between diisocyanate and the hydroxyl groups on the surface of PDMS sheet led to the formation of urethane group. Afterwards the hydroxyl group on the poly (ethylene glycol) methyl ether (MPEG ) was reacted with the remaining unreacted isocyanate, and grafted on the surface of PDMS sheet. According to the FTIR analysis, the appearance of the absorption peak at 3330cm-1, assigned to -NHCOO-from the urethane group, indicate that the PDMS sheet was reacted with diisocyanate successfully, and the disappearance of the absorption peak at 2270cm-1 corrobates that the MPEG was grafted on the surface of PDMS sheet successfully. The contact angle of modified samples was smaller, thus indicating that the hydrophilic modification was successful. Surface analysis by AFM and thermal analysis by DSC and TGA have also been conducted.

Thesis (Ph.D.)--State University of New York at Buffalo, 2007.
Title from PDF title page (viewed on Nov. 16, 2007) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Gardella, Joseph A., Jr. Includes bibliographical references.

Mechanical forces have been observed to affect various aspects of life, for example, cell differentiation, cell migration, locomotion and behavior of multicellular organisms etc. Such forces are generated either by external entities such as mechanical touch, fluid flow, electric and magnetic fields or by the living organisms themselves. Study of forces sensed and applied by living organisms is important to understand the interactions between organisms and their environment. Such studies may reveal molecular mechanisms involved in mechanosensation and locomotion. Several techniques have been successfully applied to measure forces exerted by single cells and cell monolayers. The earliest technique made use of functionalized soft surfaces and membranes as substrates on which cell monolayers were grown. The forces exerted by the cells could be measured by observing deformation of the substrates. Atomic Force Microscope (AFM) is another sensitive instrument that allows one to exert and measure forces in pico-Newton range. Advances in micromachining technology have enabled development of miniature force sensors and actuators. Latest techniques for mechanical force application and measurement use micromachined Silicon cantilevers in single as well as array form and micropillar arrays. Micropillar arrays fabricated using soft lithography enabled the use of biocompatible materials for force sensors. Together, these techniques provide access to a wide range of forces, from sub micro-Newton to milli-Newton. In the present work, types of forces experienced in biological systems and various force measurement and actuation techniques will be introduced. This will be followed by in depth description of the two major contributions of this thesis, 1) ―Colored polydimethylsiloxane micropillar arrays for high throughput measurements of forces applied by genetic model organisms‖. Biomicrofluidics, January 29, 2015. doi: 10.1063/1.4906905 2) ―Air microjet system for non-contact force application and the actuation of micro-structures‖. Journal of micromechanics and microengineering, December 15, 2015. doi: 10.1088/0960-1317/26/1/017001 Device developed for force measurement consists of an array of micropillars made of a biocompatible polymer Poly Dimethyl Siloxane (PDMS). Such devices have been used by researchers to measure traction forces exerted by single cells and also by nematode worm Caenorhabditis elegans (C. elegans). C. elegans is allowed to move in between the micropillars and the locomotion is video recorded. Deflection of the micropillar tips as the worm moves is converted into force exerted. Transparent appearance of C. elegans and PDMS poses difficulties in distinguishing micropillars from the worm, thus making it challenging to automate the analysis process. We address this problem by developing a technique to color the micropillars selectively. This enabled us to develop a semi-automated graphical user interface (GUI) for high throughput data extraction and analysis, reducing the analysis time for each worm to minutes. Moreover, increased contrast because of the color also delivered better images. Addition of color changed the Young‘s modulus of PDMS. Thus the dye-PDMS composite was characterized using hyper-elastic model. The micropillars were also calibrated using commercial force sensor. Analysis of forces exerted by wild type and mutant C. elegans moving on an agarose surface was performed. Wild type C. elegans exerted a total average force of 7.68 µN and an average force of ~1 µN on an individual pillar. We show that the middle of C. elegans exerts more force than its extremities. We find that C. elegans mutants with defective body wall muscles apply significantly lower force on individual pillars, while mutants defective in sensing externally applied mechanical forces still apply the same average force per pillar compared to wild type animals. Average forces applied per pillar are independent of the length, diameter, or cuticle stiffness of the animal. It was also observed that the motility of the worms with mechanosensation defects, lower cuticle stiffness, and body wall muscle defects was reduced with worms that have defective body wall muscle having the largest degree. Thus, we conclude that while reduced ability to apply forces affects the locomotion of the worm in the micropillar array, the reduced motility/locomotion may not indicate that the worm has reduced ability to apply forces on the micropillars. We also used the colored micropillar array for the first time to measure forces exerted by Drosophila larvae. Our device successfully captured the peristaltic rhythm of the body wall muscles of the larva and allowed us to measure the forces applied on each deflected pillar during this motion. Average force exerted by 1st instar wild type Drosophila larvae was measured to be ~ 1.5 µN per pillar. We demonstrated that a microjet of air can be used to apply forces in micro-Newton range. We developed a standalone system to generate a controlled air microjet. Microjet was generated using a controlled electromagnetic actuation of a diaphragm. With a nozzle diameter of 150 µm, the microjet diameter was maintained to a maximum of 1 mm at a distance of 5 mm from the nozzle. The force generated by the microjet was measured using a commercial force sensor to determine the velocity profile of the jet. Axial flow velocities of up to 25 m/s were obtained at distances as long as 6 mm. The microjet exerted a force up to 1 µN on a poly dimethyl siloxane (PDMS) micropillar (50 µm in diameter, 157 µm in height) and 415 µN on a PDMS membrane (3 mm in diameter, 28 µm thick). We also demonstrate that from a distance of 6 mm our microjet can exert a peak pressure of 187 Pa with a total force of about 84 µN on a flat surface with 8 V operating voltage. Next, we demonstrated that the response of C. elegans worms to the impinging air microjet is similar to the response evoked using a manual gentle touch. This contactless actuation tool avoids contamination and mechanical damage to the samples. Out of the cleanroom fabrication and robust design make this system cost effective and durable. Magnetic micropillars have been used as actuators. We fabricated magnetic micropillar arrays and designed actuation mechanisms using permanent magnet and a pulsed electromagnet. Force of about 19 µN was achievable using a permanent magnet actuation. In a pulsed electromagnetic field micropillar exerted a force of about 10 µN on a commercial force sensor. These techniques have promising applications when actuation needs to be controlled from long distances.

Trabalho de Projeto do Mestrado Integrado em Engenharia Biomédica apresentado à Faculdade de Ciências e Tecnologia
O ambiente biológico no qual as células residem in vivo é altamente organizado da nano à micro e macroescala. Nas últimas décadas, tem vindo a ser demonstrado que as células conseguem sentir e responder ao seu microambiente, especialmente a estímulos físicos e sinais químicos. No que diz respeito aos estímulos físicos, a topografia e rigidez da superfície têm demonstrado influenciar fortemente o comportamento celular. Esta dissertação teve como objetivo principal modificar a topografia de superfície do poli (dimetilsiloxano) (PDMS) através da deposição de filmes finos por pulverização catódica e testar in vitro as superfícies obtidas para concluir acerca do comportamento celular. Filmes finos de poli (tetrafluoroetileno) (PTFE) e poliamida (PA) foram depositados em substratos de PDMS previamente tracionados. Padrões ordenados de rugas foram obtidos a uma escala micrométrica, assim como rugosidade à escala nanométrica. Os filmes criados foram caracterizados química, física e mecanicamente e ensaios mecânicos foram realizados. As rugas permaneceram após tracção cíclica das amostras. Finalmente, as superfícies foram testadas in vitro com células estaminais mesenquimais do cordão umbilical humano (hUC-MSCs). As células foram capazes de aderir, proliferar e diferenciar-se quando cultivadas no PDMS modificado com PTFE e PA. Além disso, foi verificado o alinhamento celular induzido pela topografia enrugada dos filmes. O trabalho desenvolvido neste projeto tem o potencial de ser utilizado em muitas aplicações biomédicas para cultura de células, detecção/screening celular, implantação, engenharia de tecidos, microfluidos e biosensores.
The biological environment in which cells reside in vivo is highly organized from the nano- to the micro- and macroscale. Over the past decades, it has been demonstrated that cells can sense and respond to their microenvironment, especially to physical stimuli and chemical signals. Among the physical cues, surface topography and stiffness have shown to strongly influence cell behavior.This dissertation had the main purpose of modifying the surface topography of poly(dimethylsiloxane) (PDMS) through the deposition of thin films by magnetron sputtering and test in vitro the surfaces obtained to conclude on cellular behavior. Thin films of poly(tetrafluoroethylene) (PTFE) and polyamide (PA) were deposited onto previously strained PDMS substrates. Ordered wrinkling patterns were obtained at the microscale, as well as nanometric roughness. The films created were chemically, physically and mechanically characterized and mechanical tests were performed. The wrinkles remained after cyclic straining the samples. Finally, the samples were tested in vitro with human umbilical cord mesenchymal stem cells (hUC-MSCs). Cells were able to adhere, proliferate and differentiate into the osteogenic lineage on the PTFE and PA modified PDMS. Furthermore, cell alignment was induced by the films wrinkled topography.The work developed in this project has the potential to be used in many biomedical applications for cell culture, cell detection/screening, implantation, tissue engineering, microfluidics and biosensors.
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