Academic literature on the topic 'Polymer cushion'
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Journal articles on the topic "Polymer cushion"
1
Liu, Yingfeng, Qiong Rao, Ming Chen, Xiongqi Peng, and Shaoqing Shi. "A Visco-Hyperelastic Constitutive Model for Multilayer Polymer Membranes and its Application in Packaging Air Cushion." International Journal of Applied Mechanics 08, no. 05 (July 2016): 1650062. http://dx.doi.org/10.1142/s1758825116500629.
Full textAbstract:
Air cushion is an important packaging material with admirable cushion property in protecting articles from damage. Polymer membrane in air cushion renders a highly nonlinear elastic and rate dependent mechanical behavior in experimental tensile test. A visco-hyperelastic constitutive model for a polymer membrane of an air cushion is developed by additively decomposing its mechanical response into a hyperelastic portion and a viscoelastic portion. Material parameters are consecutively obtained by matching experimental data of static and dynamic uni-axial tensile tests of the membrane, respectively. Compression test of a single air column of the air cushion is conducted as a means of validation on the proposed constitutive model. By comparing simulation results with experimental data, it is shown that the proposed visco-hyperelastic model can properly characterize the mechanical behavior of the air cushion packaging material. The model can be applied to evaluate cushion performance of air cushions and their optimum design.
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Ryzhkov, Nikolay V., and Ekaterina V. Skorb. "A platform for light-controlled formation of free-stranding lipid membranes." Journal of The Royal Society Interface 17, no. 163 (February 2020): 20190740. http://dx.doi.org/10.1098/rsif.2019.0740.
Full textAbstract:
The engineering of artificial cells is one of the most significant scientific challenges. Thus, controlled fabrication and in situ monitoring of biomimetic nanoscale objects are among the central issues in current science and technology. Studies of transmembrane channels and cell mechanics often require the formation of lipid bilayers (LBs), their modification and their transfer to a particular place. We present here a novel approach for remotely controlled manipulation of LBs. Layer-by-layer deposition of polyethyleneimine and poly(sodium 4-styrenesulfonate) on a nanostructured TiO 2 photoanode was performed to obtain a surface with the desired net charge and to enhance photocatalytic performance. The LB was deposited on top of a multi-layer positive polymer cushion by the dispersion of negative vesicles. The separation distance between the electrostatically linked polyelectrolyte cushion and the LB can be adjusted by changing the environmental pH, as zwitter-ionic lipid molecules undergo pH-triggered charge-shifting. Protons were generated remotely by photoanodic water decomposition on the TiO 2 surface under 365 nm illumination. The resulting pH gradient was characterized by scanning vibrating electrode and scanning ion-selective electrode techniques. The light-induced reversible detachment of the LB from the polymer-cushioned photoactive substrate was found to correlate with suggested impedance models.
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Wang, Ju Wei. "Lignin Waste Polyurethane Cushion Packaging Materials Research." Applied Mechanics and Materials 488-489 (January 2014): 98–101. http://dx.doi.org/10.4028/www.scientific.net/amm.488-489.98.
Full textAbstract:
Polyurethane (referred to as PU) is a polymer made from polyisocyanate and a polyether polyol or polyester polyol and small molecule polyol, polyamine or water chain extenders or crosslinking agent, such as raw materials. By changing the type of material and composition, you can dramatically change the form of products and their performance, the final product from soft to hard. Lignin, a natural renewable resources, natural aromatic polymer has a hydroxyl-containing three-dimensional structural characteristics, the research and application has become increasingly active. The introduction of the lignin in the material, not only can improve the performance of the material but also reduce costs, resulting in considerable economic benefits. If we can combine the two advantages of the manufacture of composite materials to become a demand. The subjects explored the impact of the alkali lignin waste polyurethane foam and curing agent on the performance of the polyurethane foam through experiments that the above factors, the ratio of the manufacture of polyurethane foam: phenolic resin 250g, adding emulsifier 30g, foamagent alkali lignin 40g, waste polyurethane 30g, hardener 100g from the foam strength of 380KPa and low cost.
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Wang, Jun, Li-xin Lu, Huan-xin Jiang, and Yong Zhu. "Nonlinear Response of Strong Nonlinear System Arisen in Polymer Cushion." Abstract and Applied Analysis 2013 (2013): 1–3. http://dx.doi.org/10.1155/2013/891914.
Full textAbstract:
A dynamic model is proposed for a polymer foam-based nonlinear cushioning system. An accurate analytical solution for the nonlinear free vibration of the system is derived by applying He's variational iteration method, and conditions for resonance are obtained, which should be avoided in the cushioning design.
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Zhang, Yibang, Yanyan Chen, and Gang Jin. "PEGylated Phospholipid Membrane on Polymer Cushion and Its Interaction with Cholesterol." Langmuir 26, no. 13 (July 6, 2010): 11140–44. http://dx.doi.org/10.1021/la100973p.
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Zhang, Jianfeng, Peipei He, Yichen Lin, Haixia Song, Hao Dong, Xuejun Zhu, and Jiejing Zhang. "The Cushion Performance of Mycelium-Cornstraw Biofoams." Journal of Biobased Materials and Bioenergy 13, no. 4 (August 1, 2019): 484–89. http://dx.doi.org/10.1166/jbmb.2019.1876.
Full textAbstract:
Biofoams are considered to be one of the best alternatives to polymer foam. In many biofoams, mycelium-based biofoams are favored in the recent years for its zero pollution and renewability during the forming and after treatment process. Mycelium-wood biofoams, mycelium-cottonseed shell biofoams have been proved to have good mechanical or sound absorption properties. While, whether corn straw, as the by-product of the largest yield of agricultural products, is suitable to prepare mycelium-based biofoam has not been studied yet. Here we used Pleurotus ostreatus mycelium bonding corn straw to prepare mycelium-cornstraw biofoams, and mechanical properties as well as bonding mechanism of the mycelium-cornstraw biofoams were studied. It was discovered that inoculum quantity was an important factor on the performance of mycelium-cornstraw biofoams, and inoculum quantity of 1.8% was considered as the optimal inoculum quantity. At this inoculum quantity, when relative deformation was 10%, the compressive strength of mycelium-cornstraw biofoam was about twice that of mycelium-broadleaf sawdust biofoams reported, but the time spent on material preparation is only about their 1/3.
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Giannino, Valentina, Lucia Salandin, Cristina Macelloni, and Luigi Maria Longo. "Evaluation of Eleview® Bioadhesive Properties and Cushion-Forming Ability." Polymers 12, no. 2 (February 5, 2020): 346. http://dx.doi.org/10.3390/polym12020346.
Full textAbstract:
Submucosal injection is generally required for both endoscopic-mucosal resection (EMR) and submucosal dissection (ESD). SIC-8000 (Eleview®) is a new liquid composition in the form of a microemulsion for submucosal injection, approved by the Food and Drug Administration (FDA) 510(k) and Conformité Européene (CE) marked, containing a biocompatible polymer as a cushioning agent. The aim of this study was to evaluate Eleview®’s performance in terms of bioadhesive properties and cushion-forming ability. The bioadhesion was evaluated by measuring the interaction between Eleview® and the extracellular matrix (the main component of the submucosal layer) using the texture analyzer. To better comprehend the mechanism of action of Eleview® after submucosal injection, force of detachment and adhesion work were measured for the following formulations: Eleview®, Eleview® without poloxamer (functional polymer), poloxamer solution alone, normal saline, and MucoUp® (competing product on the Japanese market). The results obtained show the interaction between Eleview® and the extracellular matrix, highlighting the stronger bioadhesive properties of Eleview® compared with Eleview® without poloxamer, poloxamer solution alone, as well as normal saline and MucoUp®. The ability of Eleview® to form a consistent and long-lasting cushion in situ, once injected into the submucosal layer, was tested ex vivo on a porcine stomach. The results obtained show a better permanence in situ for the product compared with normal saline injection and to MucoUp® (t-test, p < 0.05).
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Merzlyakov, Mikhail, Edwin Li, Ivan Gitsov, and Kalina Hristova. "Surface-Supported Bilayers with Transmembrane Proteins: Role of the Polymer Cushion Revisited." Langmuir 22, no. 24 (November 2006): 10145–51. http://dx.doi.org/10.1021/la061976d.
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Hayama, Masayo, Kenichiro Yamamoto, Fukashi Kohori, Makoto Fukuda, Tatsuo Hiyoshi, and Kiyotaka Sakai. "“CUSHION EFFECT” OF POLYVINYLPIRROLIDONE POLYMER PARTICLES IMPROVES BIOCOMPATIBILITY OF POLYSULFONE DIALYSIS MEMBRANES." ASAIO Journal 49, no. 2 (March 2003): 201. http://dx.doi.org/10.1097/00002480-200303000-00240.
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Zhou, Jun. "Comment on “Nonlinear Response of Strong Nonlinear System Arisen in Polymer Cushion”." Abstract and Applied Analysis 2013 (2013): 1–3. http://dx.doi.org/10.1155/2013/329638.
Full textDissertations / Theses on the topic "Polymer cushion"
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Mulligan, Kirk M. "Development of New Supported Bilayer Platforms for Membrane Protein Incorporation." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24022.
Full textAbstract:
Membranes are essential components of all living organisms forming the borders of cells and their organelles. Planar lipid membranes deposited on solid substrates (solid supported membranes) provide models to study the functions of membrane proteins and are used as biosensing platforms. However, despite remarkable progress, solid supported membranes are not stable to harsh conditions such as dehydration, high temperature and pressure, and mechanical stress. In addition, the direct deposition of membranes onto a solid substrate often causes restricted mobility and denaturation of reconstituted membrane proteins.
Membrane stability can be addressed by altering the structure of the component lipids. Bolalipids are an interesting class of bipolar lipids that have been proposed for biosensing applications. Membranes formed from mixtures of a bolalipid, C20BAS, and dioleoylphosphaphatidylcholine, POPC, were characterized by atomic force spectroscopy (AFM). The lipid mixtures produced a phase separated membrane consisting of thinner bolalipid-rich and thicker monopolar-rich POPC regions, with a height difference of approximately 1-2 nm. This confirmed an earlier prediction that some bolalipid/PC membranes would phase separate due to the hydrophobic mismatch between the two lipids. Interestingly, the surface coverage of the two phases was inconsistent with what one would expect from the initial starting lipid ratios. The complex membrane morphologies observed were accredited to the interplay of several factors, including a compositionally heterogeneous vesicle population, exchange of lipid between the vesicle solution and solid substrate during formation of the supported membrane, and slow equilibration of domains due to pinning of the lipids to the solid support.
Decoupling the membrane from its underlying surface is one strategy to maintain the structure and mobility of membrane proteins. This decoupling can be achieved by depositing the membrane on a soft cushion composed of a water swelling hydrophilic polymer. A polyelectrolyte multilayer (PEM) and a tethered poly(ethylene) glycol (PEG) polymer are the two types of polymer cushions used in this study. The PEMs consist of the charged polysaccharides, chitosan (CHI) and hyaluronic acid (HA) which offer the advantage of biocompatibility over synthetic PEMs. DOPC lipid bilayers were formed at pH 4 and 6.5 on (CHI/HA)5 films. At higher pH adsorbed lipids had low mobility and large immobile lipid fractions; fluorescence and AFM showed that this was accredited to the formation of poor quality membranes with defects and pinned lipids rather than to a layer of surface-adsorbed vesicles. However, more uniform bilayers with mobile lipids were produced at pH 4. Measured diffusion coefficients were similar to those for bilayers on PEG cushions and considerably higher than those measured on other polyelectrolyte films. The results suggest that the polymer surface charge is more important than the surface roughness in controlling formation of mobile supported bilayers.
The suitability of polymer supported membranes for the incorporation of integral membrane proteins was also assessed. The integral membrane protein Ste14p, a 26 kDa methyltransferase enzyme, was reconstituted into POPC membranes on PEM and PEG supports. A combination of fluorescence microscopy, FRAP, AFM and an in situ methyltransferase activity assay were utilized to characterize the protein incorporated polymer supported membranes. Fluorescence measurements showed that more protein was incorporated in model membranes formed on the PEG support, compared to either glass or PEM cushions. However, the protein activity on a PEG support was comparable to that of the protein in a membrane on glass. FRAP measurements showed that the lipid mobilities of the POPC:Ste14p bilayers on the various supports were also comparable.
Lastly, as a new platform for manipulating and handling membrane proteins, nanodiscs containing reconstituted Ste14p were studied. Nanodiscs are small, soluble and stable bilayer discs that permit the study of membrane proteins in a uniform phospholipid bilayer environment. Empty and protein containing nanodiscs were deposited on a mica surface and imaged by AFM. AFM showed that protein containing samples possessed two subpopulations of nanodiscs with a height difference of ~1 nm. The taller discs, ~20% of the population, contained protein. Other experiments showed that the packing of the nanodisc samples was influenced by their initial stock concentration and that both imaging force and the addition of Mg2+ caused formation of larger bilayer patches.
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Renner, Lars. "Polymer Supported Lipid Bilayer Membranes for the Integration of Transmembrane Proteins." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1241457489091-02157.
Full textAbstract:
This work reports on the successful formation of supported multicomponent lipid bilayer membranes (sLBMs) from natural occurring lipids as well as synthetic lipids on a set of polymer cushions consisting of alternating maleic acid copolymers. Maleic acid copolymers provide a versatile platform to adjust the physico-chemical behaviour by the choice of the comonomer unit. The formation of sLBMs was triggered by a transient reduction of the electrostatic repulsion between the polymer cushions and the lipid vesicles by lowering the solutions pH to 4. Upon formation the stability of sLBMs was not affected by subsequent variations of the environmental pH to 7.2. Even drastic changes in the environmental pH (between pH 2 and pH 9) did not lead to delamination and proved the stability of the polymer sLBM. The degree of hydrophilicity and swelling of the anionic polymer cushions was found to determine both the kinetics of the membrane formation and the mobility of the lipid bilayer with lipid diffusion coefficients in the range from 0.26 to 2.6 µm2 s-1. An increase in cushion hydrophilicity correlated with a strong increase in the diffusion coefficient of the lipids. This trend was found to correlate with the kinetics of bilayer formation in the process of vesicle spreading. The observations strongly support the important role of the support’s polarity for the fluidity of the sLBM, which is probably related to the presence of a water layer between support and bilayer. The investigated polymer cushions are considered to open new options for the in situ modulation of lipid bilayer membranes characteristics to match the requirements for the successful integration of functional transmembrane proteins (TMPs). As each cushion exhibits different physico-chemical properties, the resulting behaviour of the sLBMs and TMPs could be exactly adjusted to the specific requirements of biological samples. This is exemplarily shown by the integration of the TMP beta amyloid precursor protein cleaving enzyme (BACE). Integrated BACE was observed to be mobile on all polymer cushions. On the contrary, no lateral mobility of BACE was found in solid sLBM. Furthermore, the activity of integrated BACE was analysed by the cleavage of an amyloid precursor protein analogue. Remarkably, the polymer cushions did not only enhance the mobility but were also found to increase the activity of BACE by a factor of 1.5 to 2.5 in comparison to solid sLBM. From the obtained results it is obvious that even small cytoplasmic domains of transmembrane proteins might not be preserved upon the integration in silica sLBM. The observed beneficial effects of the utilised polymer cushions on the mobility and activity of transmembrane proteins motivate further studies to clarify the general applicability of the polymer platform. Altogether, this polymer platform provides valuable options to form sLBM with varying characteristics to reconstitute transmembrane proteins for a wide range of possible future applications in biologyDie vorliegende Arbeit beschreibt die Bildung von polymer unterstützten Lipiddoppelschichten zur Integration von transmembranen Proteinen. Das Polymerkissensystem besteht aus alternierenden Maleinsäurecopolymeren. Lipiddoppelschichten wurden durch die Steuerung der elektrostatischen Repulsion erzeugt: die Verringerung des pH-Wertes auf 4 wurde eine Erhöhung der adsorbierten Vesikelmenge auf den Polymeroberflächen induziert. Nach der erfolgten Bildung der Lipiddoppelschichten kann der pH-Wert beliebig variiert werden, ohne dass die Stabilität der Lipiddoppelschichten beeinflusst wird. Auch drastische Veränderungen des pH-Milieus (pH 2 - pH 9) führten zu keinen Veränderungen in der Membranintegrität. Der Grad der Hydrophilie und der Quellung der anionischen Polymerschichten beeinflusst sowohl die Bildung der Modellmembranen als auch die Mobilität der integrierten Lipidmoleküle. Dabei reichen die erzielten Lipiddiffusionskoeffizienten von 0.26 bis 2.6 µm2 s-1. Dabei ist die Mobilität direkt von der Hydrophilie des Substrates abhängig. Die beobachteten Ergebnisse zeigen deutlich die entscheidende Rolle der Polarität der verwendeten Substratoberflächen auf die Lipidmobilität, die sehr wahrscheinlich mit der Präsenz einer variablen Wasserschicht zusammenhängt. Die untersuchten Polymerkissen eröffnen neue Möglichkeiten für die insitu Modulierung der Charakteristika von Lipidschichten, um funktionale transmembrane Proteine zu integrieren. Aufgrund der unterschiedlichen physiko-chemischen Eigenschaften kann das Verhalten der Lipidschichten und der transmembranen Proteine nach den spezifischen Anforderungen des Modellsystems angepasst werden. Die funktionale Integration wurde am Beispiel des transmembranen Proteins BACE nachempfunden. Die Mobilität des integrierten BACE wurde auf allen Polymerkissen beobachtet. Im Gegensatz dazu wurde auf harten Substraten keine BACE Mobilität gefunden. Die Aktivität des integrierten BACE wurde durch die enzymatische Spaltung eines APP-Analogons nachgewiesen. Bemerkenswerteweise wurde ein Anstieg der BACE Aktivität auf den Polymerkissen um den Faktor 1,5 bis 2,5 im Vergleich zu den auf harten Substraten integrierten BACE beobachtet. Zusammenfassend, die verwendeten Polymerkissen bieten vielfältige Möglichkeiten Lipidschichten mit variierenden Eigenschaften für die Integration von transmembranen Proteinen zu erzeugen
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Kaufmann, Martin. "Lipid Bilayers Supported by Multi-Stimuli Responsive Polymers." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-106231.
Full textAbstract:
Artificial lipid bilayers formed on solid surface supports are widespread model systems to study physical, chemical, as well as biological aspects of cell membranes and fundamental interfacial interactions. The approach to use a thin polymer film representing a cushion for lipid bilayers prevents incorporated membrane proteins from pinning to the support and mimics the native environment of a lipid bilayer in certain aspects of the extracellular matrix and intracellular structures. A key component for cell anchorage to extracellular fibronectin is the transmembrane adhesion receptor alpha(5)beta(1) integrin. Its transport dynamics and clustering behavior plays a major role in the assembly of focal adhesions, which mediate mechanical forces and biochemical signals of cells with their surrounding.
The system investigated herein is envisioned to use extrinsically controlled stimuli-responsive polymer cushions to tune the frictional drag between polymer cushion and mobile membranes with incorporated integrins to actively regulate lipid membrane characteristics. To attain this goal, a temperature- and pH-responsive polymer based on poly(N-isopropylacrylamide) copolymers containing varying amounts of carboxyl-group-terminated comonomers at different aliphatic spacer lengths (PNIPAAm-co-carboxyAAM) was surface-grafted to a poly(glycidyl methacrylate) anchorage layer. The swelling transitions were characterized using atomic force microscopy, ellipsometry and quartz crystal microbalance with dissipation monitoring (QCM-D) and found to be tunable over a wide range of temperature and pH. In agreement with the behavior of the polymers in solution, longer alkyl spacers decreased the phase transition temperature T(P) and higher contents of carboxylic acid terminated comonomers increased T(P) at alkaline conditions and decreased T(P) at acidic conditions. Remarkably, the point where the degree of carboxyl group deprotonation balances the T(P)-lowering effect of the alkyl spacer was distinctive for each alkyl spacer length.
These findings illustrate how the local and global balance of hydrophilic and hydrophobic interactions along the copolymer chain allows to adjust the swelling transition to temperatures below, comparable, or above those observed for PNIPAAm homopolymers. Additionally, it could be shown that surface-grafting leads to a decrease in T(P) for PNIPAAm homopolymers (7°C) and copolymers (5°C - 10°C). The main reason is the increase in local polymer concentration of the swollen film constrained by dense surface anchorage in comparison to the behavior of dilute free chains in solution. In accordance with the Flory-Huggins theory, T(P) decreases with increasing concentration up to the critical concentration. Biological functionalization of the PNIPAAm-co-carboxyAAm thin films was demonstrated for the cell adhesion ligand peptide cRGD via carbodiimide chemistry to mimic extracellular binding sites for the cell adhesion receptors integrin.
The outcome of QCM-D measurements of cRGD-functionalized surfaces showed a maintained stimuli-responsiveness with slight reduction in T(P). A drying/rehydration procedure of a 9:1 lipid mixture of the cationic lipid dioleoyl-trimethylammoniumpropane (DOTAP) and the zwitterionic dioleoyl-phosphatidylcholine (DOPC) was utilized to form lipid bilayer membranes on PNIPAAm-co-carboxyAAM cushions. Fluorescence recovery after photobleaching (FRAP) revealed that lipid mobility was distinctively higher (6.3 - 9.6) µm2 s-1 in comparison to solid glass support ((3.0 - 5.9) µm2 s-1). In contradiction to the initial expectations, modulation of temperature and pH led to poor variations in lipid mobility that did not correlate with the PNIPAAm cushion swelling state. The results suggested a weak coupling of the lipid bilayer with PNIPAAm polymer cushions that can be slightly tuned by electrostatic interactions.
The transmembrane adhesion receptor alpha(5)beta(1) integrin was reconstituted into liposomes consisting of DOPC/sphingomyelin/cholesterol 2:2:1 for the formation of polymer cushioned bilayers. PNIPAAm- co-carboxyAAM and maleic acid (MA) copolymers were used as cushions, both with the option for cRGD functionalization. On the MA copolymer cushions, fusion of proteoliposomes resulted in supported bilayers with mobile lipids as confirmed by FRAP. However, incorporated integrins were immobile. In an attempt to explain this observation, the medium-sized cytoplasmic integrin domain was accounted to hamper the movement by steric interactions with the underlying polymer chains in conjunction with electrostatic interactions of the cationic cytoplasmic domain with the oppositely charged MA copolymer.
On the PNIPAAm-co-carboxyAAM cushion only a drying/rehydration procedure lead to bilayer formation. However, again the integrins were immobile, presumably due to the harsh treatment during preparation. Nevertheless, the results of the investigated set of PNIPAAm copolymer films suggest their application as temperature- and pH-responsive switchable layers to control interfacial phenomena in bio-systems at different physiological conditions. The PNIPAAm-co-carboxyAAm cushioned bilayer system represents a promising step towards extrinsically controlled membrane – substrate interactions.
4
Renner, Lars. "Polymer Supported Lipid Bilayer Membranes for the Integration of Transmembrane Proteins." Doctoral thesis, 2008. https://tud.qucosa.de/id/qucosa%3A23741.
Full textAbstract:
This work reports on the successful formation of supported multicomponent lipid bilayer membranes (sLBMs) from natural occurring lipids as well as synthetic lipids on a set of polymer cushions consisting of alternating maleic acid copolymers. Maleic acid copolymers provide a versatile platform to adjust the physico-chemical behaviour by the choice of the comonomer unit. The formation of sLBMs was triggered by a transient reduction of the electrostatic repulsion between the polymer cushions and the lipid vesicles by lowering the solutions pH to 4. Upon formation the stability of sLBMs was not affected by subsequent variations of the environmental pH to 7.2. Even drastic changes in the environmental pH (between pH 2 and pH 9) did not lead to delamination and proved the stability of the polymer sLBM. The degree of hydrophilicity and swelling of the anionic polymer cushions was found to determine both the kinetics of the membrane formation and the mobility of the lipid bilayer with lipid diffusion coefficients in the range from 0.26 to 2.6 µm2 s-1. An increase in cushion hydrophilicity correlated with a strong increase in the diffusion coefficient of the lipids. This trend was found to correlate with the kinetics of bilayer formation in the process of vesicle spreading. The observations strongly support the important role of the support’s polarity for the fluidity of the sLBM, which is probably related to the presence of a water layer between support and bilayer. The investigated polymer cushions are considered to open new options for the in situ modulation of lipid bilayer membranes characteristics to match the requirements for the successful integration of functional transmembrane proteins (TMPs). As each cushion exhibits different physico-chemical properties, the resulting behaviour of the sLBMs and TMPs could be exactly adjusted to the specific requirements of biological samples. This is exemplarily shown by the integration of the TMP beta amyloid precursor protein cleaving enzyme (BACE). Integrated BACE was observed to be mobile on all polymer cushions. On the contrary, no lateral mobility of BACE was found in solid sLBM. Furthermore, the activity of integrated BACE was analysed by the cleavage of an amyloid precursor protein analogue. Remarkably, the polymer cushions did not only enhance the mobility but were also found to increase the activity of BACE by a factor of 1.5 to 2.5 in comparison to solid sLBM. From the obtained results it is obvious that even small cytoplasmic domains of transmembrane proteins might not be preserved upon the integration in silica sLBM. The observed beneficial effects of the utilised polymer cushions on the mobility and activity of transmembrane proteins motivate further studies to clarify the general applicability of the polymer platform. Altogether, this polymer platform provides valuable options to form sLBM with varying characteristics to reconstitute transmembrane proteins for a wide range of possible future applications in biology.Die vorliegende Arbeit beschreibt die Bildung von polymer unterstützten Lipiddoppelschichten zur Integration von transmembranen Proteinen. Das Polymerkissensystem besteht aus alternierenden Maleinsäurecopolymeren. Lipiddoppelschichten wurden durch die Steuerung der elektrostatischen Repulsion erzeugt: die Verringerung des pH-Wertes auf 4 wurde eine Erhöhung der adsorbierten Vesikelmenge auf den Polymeroberflächen induziert. Nach der erfolgten Bildung der Lipiddoppelschichten kann der pH-Wert beliebig variiert werden, ohne dass die Stabilität der Lipiddoppelschichten beeinflusst wird. Auch drastische Veränderungen des pH-Milieus (pH 2 - pH 9) führten zu keinen Veränderungen in der Membranintegrität. Der Grad der Hydrophilie und der Quellung der anionischen Polymerschichten beeinflusst sowohl die Bildung der Modellmembranen als auch die Mobilität der integrierten Lipidmoleküle. Dabei reichen die erzielten Lipiddiffusionskoeffizienten von 0.26 bis 2.6 µm2 s-1. Dabei ist die Mobilität direkt von der Hydrophilie des Substrates abhängig. Die beobachteten Ergebnisse zeigen deutlich die entscheidende Rolle der Polarität der verwendeten Substratoberflächen auf die Lipidmobilität, die sehr wahrscheinlich mit der Präsenz einer variablen Wasserschicht zusammenhängt. Die untersuchten Polymerkissen eröffnen neue Möglichkeiten für die insitu Modulierung der Charakteristika von Lipidschichten, um funktionale transmembrane Proteine zu integrieren. Aufgrund der unterschiedlichen physiko-chemischen Eigenschaften kann das Verhalten der Lipidschichten und der transmembranen Proteine nach den spezifischen Anforderungen des Modellsystems angepasst werden. Die funktionale Integration wurde am Beispiel des transmembranen Proteins BACE nachempfunden. Die Mobilität des integrierten BACE wurde auf allen Polymerkissen beobachtet. Im Gegensatz dazu wurde auf harten Substraten keine BACE Mobilität gefunden. Die Aktivität des integrierten BACE wurde durch die enzymatische Spaltung eines APP-Analogons nachgewiesen. Bemerkenswerteweise wurde ein Anstieg der BACE Aktivität auf den Polymerkissen um den Faktor 1,5 bis 2,5 im Vergleich zu den auf harten Substraten integrierten BACE beobachtet. Zusammenfassend, die verwendeten Polymerkissen bieten vielfältige Möglichkeiten Lipidschichten mit variierenden Eigenschaften für die Integration von transmembranen Proteinen zu erzeugen.
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Kaufmann, Martin. "Lipid Bilayers Supported by Multi-Stimuli Responsive Polymers." Doctoral thesis, 2012. https://tud.qucosa.de/id/qucosa%3A26659.
Full textAbstract:
Artificial lipid bilayers formed on solid surface supports are widespread model systems to study physical, chemical, as well as biological aspects of cell membranes and fundamental interfacial interactions. The approach to use a thin polymer film representing a cushion for lipid bilayers prevents incorporated membrane proteins from pinning to the support and mimics the native environment of a lipid bilayer in certain aspects of the extracellular matrix and intracellular structures. A key component for cell anchorage to extracellular fibronectin is the transmembrane adhesion receptor alpha(5)beta(1) integrin. Its transport dynamics and clustering behavior plays a major role in the assembly of focal adhesions, which mediate mechanical forces and biochemical signals of cells with their surrounding.
The system investigated herein is envisioned to use extrinsically controlled stimuli-responsive polymer cushions to tune the frictional drag between polymer cushion and mobile membranes with incorporated integrins to actively regulate lipid membrane characteristics. To attain this goal, a temperature- and pH-responsive polymer based on poly(N-isopropylacrylamide) copolymers containing varying amounts of carboxyl-group-terminated comonomers at different aliphatic spacer lengths (PNIPAAm-co-carboxyAAM) was surface-grafted to a poly(glycidyl methacrylate) anchorage layer. The swelling transitions were characterized using atomic force microscopy, ellipsometry and quartz crystal microbalance with dissipation monitoring (QCM-D) and found to be tunable over a wide range of temperature and pH. In agreement with the behavior of the polymers in solution, longer alkyl spacers decreased the phase transition temperature T(P) and higher contents of carboxylic acid terminated comonomers increased T(P) at alkaline conditions and decreased T(P) at acidic conditions. Remarkably, the point where the degree of carboxyl group deprotonation balances the T(P)-lowering effect of the alkyl spacer was distinctive for each alkyl spacer length.
These findings illustrate how the local and global balance of hydrophilic and hydrophobic interactions along the copolymer chain allows to adjust the swelling transition to temperatures below, comparable, or above those observed for PNIPAAm homopolymers. Additionally, it could be shown that surface-grafting leads to a decrease in T(P) for PNIPAAm homopolymers (7°C) and copolymers (5°C - 10°C). The main reason is the increase in local polymer concentration of the swollen film constrained by dense surface anchorage in comparison to the behavior of dilute free chains in solution. In accordance with the Flory-Huggins theory, T(P) decreases with increasing concentration up to the critical concentration. Biological functionalization of the PNIPAAm-co-carboxyAAm thin films was demonstrated for the cell adhesion ligand peptide cRGD via carbodiimide chemistry to mimic extracellular binding sites for the cell adhesion receptors integrin.
The outcome of QCM-D measurements of cRGD-functionalized surfaces showed a maintained stimuli-responsiveness with slight reduction in T(P). A drying/rehydration procedure of a 9:1 lipid mixture of the cationic lipid dioleoyl-trimethylammoniumpropane (DOTAP) and the zwitterionic dioleoyl-phosphatidylcholine (DOPC) was utilized to form lipid bilayer membranes on PNIPAAm-co-carboxyAAM cushions. Fluorescence recovery after photobleaching (FRAP) revealed that lipid mobility was distinctively higher (6.3 - 9.6) µm2 s-1 in comparison to solid glass support ((3.0 - 5.9) µm2 s-1). In contradiction to the initial expectations, modulation of temperature and pH led to poor variations in lipid mobility that did not correlate with the PNIPAAm cushion swelling state. The results suggested a weak coupling of the lipid bilayer with PNIPAAm polymer cushions that can be slightly tuned by electrostatic interactions.
The transmembrane adhesion receptor alpha(5)beta(1) integrin was reconstituted into liposomes consisting of DOPC/sphingomyelin/cholesterol 2:2:1 for the formation of polymer cushioned bilayers. PNIPAAm- co-carboxyAAM and maleic acid (MA) copolymers were used as cushions, both with the option for cRGD functionalization. On the MA copolymer cushions, fusion of proteoliposomes resulted in supported bilayers with mobile lipids as confirmed by FRAP. However, incorporated integrins were immobile. In an attempt to explain this observation, the medium-sized cytoplasmic integrin domain was accounted to hamper the movement by steric interactions with the underlying polymer chains in conjunction with electrostatic interactions of the cationic cytoplasmic domain with the oppositely charged MA copolymer.
On the PNIPAAm-co-carboxyAAM cushion only a drying/rehydration procedure lead to bilayer formation. However, again the integrins were immobile, presumably due to the harsh treatment during preparation. Nevertheless, the results of the investigated set of PNIPAAm copolymer films suggest their application as temperature- and pH-responsive switchable layers to control interfacial phenomena in bio-systems at different physiological conditions. The PNIPAAm-co-carboxyAAm cushioned bilayer system represents a promising step towards extrinsically controlled membrane – substrate interactions.
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(9226604), Amin Joodaky. "MECHANICS AND DESIGN OF POLYMERIC METAMATERIAL STRUCTURES FOR SHOCK ABSORPTION APPLICATIONS." Thesis, 2020.
Find full textAbstract:
This body of work examines analytical and numerical models to simulate the response of structures in shock absorption applications. Specifically, the work examines the prediction of cushion curves of polymer foams, and a topological examination of a $\chi$ shape unit cell found in architected mechanical elastomeric metamaterials. The $\chi$ unit cell exhibits the same effective stress-strain relationship as a closed cell polymer foam. Polymer foams are commonly used in the protective packaging of fragile products. Cushion curves are used within the packaging industry to characterize a foam's impact performance. These curves are two-dimensional representations of the deceleration of an impacting mass versus static stress. The main drawback with cushion curves is that they are currently generated from an exhaustive set of experimental test data. This work examines modeling the shock response using a continuous rod approximation with a given impact velocity in order to generate cushion curves without the need of extensive testing. In examining the $\chi$ unit cell, this work focuses on the effects of topological changes on constitutive behavior and shock absorbing performance. Particular emphasis is placed on developing models to predict the onset of regions of quasi-zero-modulus (QZM), the length of the QZM region and the cushion curve produced by impacting the unit cell. The unit cell's topology is reduced to examining a characteristic angle, defining the internal geometry with the cell, and examining the effects of changing this angle.
However, the characteristic angle cannot be increased without tradeoffs; the cell's effective constitutive behavior evolves from long regions to shortened regions of quasi-zero modulus. Finally, this work shows that the basic $\chi$ unit cell can be tessellated to produce a nearly equivalent force deflection relationship in two directions. The analysis and results in this work can be viewed as new framework in analyzing programmable elastomeric metamaterials that exhibit this type of nonlinear behavior for shock absorption.
Book chapters on the topic "Polymer cushion"
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Gooch, Jan W. "Cushion Carpet." In Encyclopedic Dictionary of Polymers, 188. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_3214.
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Gooch, Jan W. "Cushion Back Carpet." In Encyclopedic Dictionary of Polymers, 188. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_3213.
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"Cushion carpet." In Encyclopedic Dictionary of Polymers, 251. New York, NY: Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-30160-0_3160.
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"Cushion back carpet." In Encyclopedic Dictionary of Polymers, 251. New York, NY: Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-30160-0_3159.
Full textConference papers on the topic "Polymer cushion"
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Ramos Gonzalez, Maria, Brendan O’Toole, and Zhiyong Wang. "Experimental Study of Bio-Polymer Knee Implant." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-88479.
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This study tests a custom-designed knee implant made of an FDA approved biomaterial, Chronoflex AR. The implant is designed to cushion the damaged cartilage at the distal end of the femur to reduce knee pain without the removal of cartilage and bone. A patient’s MRI scan was used to render a 3D computer graphic design of the knee. The manufacturing of the implant is conducted by 3D printing the shape of the distal end of the femur and coating it with the biomaterial. This is a preliminary fabrication method. Ultimately, the implant material will be 3D printed or cast in 3D printed molds. A successful implementation of this sort of custom-designed implant would reduce the invasiveness of knee correcting procedures, enable the patient to retain the shape of his or her femoral and tibial anatomy, and reduce the possibility of revision surgeries. A custom knee implant testing machine was designed and fabricated to measure the force, elastic deformation, plastic deformation, wear and fatigue of the component after performing lab tests simulating a normal walking pattern while adhering to ISO standards.
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Carrigan, Wei, Pavan Nuthi, Charu Pande, Caleb P. Nothnagle, and Muthu B. J. Wijesundara. "A Pressure Modulating Sensorized Soft Actuator Array for Pressure Ulcer Prevention." In ASME 2017 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/detc2017-68191.
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Pressure ulcers are a serious reoccurring complication among wheelchair users with impaired mobility and sensation. It is postulated that external mechanical loading, specifically on bony prominences, is a major contributing factor in pressure ulcer formation. Prevention strategies mainly center on reducing the magnitude and duration of external forces acting upon the body. Seat cushion technologies for reducing pressure ulcer prevalence often employ soft materials and customized cushion geometries. Air cell arrays used in time-based pressure modulation techniques are seen as a promising alternative; however, this approach could be further enhanced by adding real-time pressure profile mapping to enable automated pressure modulation customizable for each user’s condition. The work presented here describes the development of a prototype support surface and pressure modulation algorithm which can monitor interface pressure as well as automatically offload and redistribute concentrated pressure. This prototype is comprised of arrays of sensorized polymeric soft air cell actuators which are modulated by a pneumatic controller. Each actuator’s pressure can be changed independently which results in a change to the interface pressure allowing us to offload targeted regions and provide local adjustment for redistribution. The pressure mapping, redistribution, and offloading capabilities of the prototype are demonstrated using pressure modulation algorithms described here.
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Liu, Wei, and Kang Tai. "Computational Geometric Modeling and Unfolding of 3-D Folded Structures." In ASME 2002 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/detc2002/dac-34046.
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Due to environmental considerations, corrugated paperboard folded into appropriate 3-D structural shapes are increasingly being used as packaging cushions, as a substitute for those traditionally made of polymer foams. However, since paperboards are manufactured in the form of sheets, 3-D structures have to be created from these boards by folding. The design of the necessary flat layout pattern of a board that can be folded into a reasonably complex and intricate shape is a process requiring a lot of costly trial-and-error and creativity on the part of the designer. This paper describes a methodology developed to aid the designer by automatically and systematically generating many possible flat layouts that can be folded into a specified 3-D folded structure. The key to such a method is a computer representation of the topology/connectivity of the faces of the 3-D folded structure by a graph-theoretic model, and an algorithm to operate on this model to unfold and generate the geometry of the planar layout. The procedure is implemented on a computer and resulting flat layout designs have been generated for four example structures. Some of the issues concerning the types of folded structures that can and cannot be easily unfolded and the types of layouts that can and cannot be generated by the current methodology are discussed.
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Tamaddoni, Nima, and Andy Sarles. "Fabrication and Characterization of a Membrane Based Hair Cell Sensor That Features Soft Hydrogel Materials." In ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-8067.
Full textAbstract:
One of the most common sensory structures in nature is the hair cell. Examples of hair cells include the inner and outer hair cells in the inner ears of vertebrates, external sensory hairs on the legs of spiders, and neuromasts found along the lateral lines of fish. Recent work by Sarles and Leo demonstrated that self-assembly methods could be used to construct a membrane-based hair cell that responds to a physical disturbance of the hair. An artificial cell membrane (or lipid bilayer) formed at the interface of two lipid-encased hydrogel volumes, serves as the transduction element in the device. In this study, a revised sensor embodiment is presented in which the hair is fixed at its base by the encapsulating polymeric substrate. In addition, a highly elastic, photo-polymerizable aqueous gel (PEGDA, 6000g/mole) is used to further increase the resiliency of the hair and to provide a compliant cushion for the bilayer. These changes yield a considerably more durable hair cell sensor. We perform a series of experimental tests to characterize the transduction element (i.e. the bilayer) and the sensing current produced by free vibration of the hair, and we study the directional sensitivity of this hair cell embodiment by perturbing the hair in three directions. These tests demonstrate that the magnitude of the sensing current (30–300pA) is significantly affected by direction of perturbation, where the largest signals result from motion of the hair in a direction perpendicular to the plane of the bilayer.
Reports on the topic "Polymer cushion"
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Maiti, A. Developing a radiation-aging model for polymeric foam cushions. Office of Scientific and Technical Information (OSTI), April 2019. http://dx.doi.org/10.2172/1512592.
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