Bibliografias temáticas / Gels and Hydrogels

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Literatura científica selecionada sobre o tema "Gels and Hydrogels"

Autor: Grafiati

Publicado: 23 de novembro de 2024

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Artigos de revistas sobre o assunto "Gels and Hydrogels"

Xu, Bo, Yuwei Liu, Lanlan Wang, Xiaodong Ge, Min Fu, Ping Wang e Qiang Wang. "High-Strength Nanocomposite Hydrogels with Swelling-Resistant and Anti-Dehydration Properties". Polymers 10, n.º 9 (14 de setembro de 2018): 1025. http://dx.doi.org/10.3390/polym10091025.

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Hydrogels with excellent mechanical properties have potential for use in various fields. However, the swelling of hydrogels under water and the dehydration of hydrogels in air severely limits the practical applications of high-strength hydrogels due to the influence of air and water on the mechanical performance of hydrogels. In this study, we report on a kind of tough and strong nanocomposite hydrogels (NC-G gels) with both swelling-resistant and anti-dehydration properties via in situ free radical copolymerization of acrylic acid (AA) and N-vinyl-2-pyrrolidone (VP) in the water-glycerol bi-solvent solutions containing small amounts of alumina nanoparticles (Al2O3 NPs) as the inorganic cross-linking agents. The topotactic chelation reactions between Al2O3 NPs and polymer matrix are thought to contribute to the cross-linking structure, outstanding mechanical performance, and swelling-resistant property of NC-G gels, whereas the strong hydrogen bonds between water and glycerol endow them with anti-dehydration capacity. As a result, the NC-G gels could maintain mechanical properties comparable to other as-prepared high-strength hydrogels when utilized both under water and in air environments. Thus, this novel type of hydrogel would considerably enlarge the application range of hydrogel materials.

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Burchak, Vadym, Fritz Koch, Leonard Siebler, Sonja Haase, Verena K. Horner, Xenia Kempter, G. Björn Stark et al. "Evaluation of a Novel Thiol–Norbornene-Functionalized Gelatin Hydrogel for Bioprinting of Mesenchymal Stem Cells". International Journal of Molecular Sciences 23, n.º 14 (19 de julho de 2022): 7939. http://dx.doi.org/10.3390/ijms23147939.

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Introduction: Three-dimensional bioprinting can be considered as an advancement of the classical tissue engineering concept. For bioprinting, cells have to be dispersed in hydrogels. Recently, a novel semi-synthetic thiolene hydrogel system based on norbornene-functionalized gelatin (GelNB) and thiolated gelatin (GelS) was described that resulted in the photoclick hydrogel GelNB/GelS. In this study, we evaluated the printability and biocompatibility of this hydrogel system towards adipose-tissue-derived mesenchymal stem cells (ASCs). Methods: GelNB/GelS was synthesized with three different crosslinking densities (low, medium and high), resulting in different mechanical properties with moduli of elasticity between 206 Pa and 1383 Pa. These hydrogels were tested for their biocompatibility towards ASCs in terms of their viability, proliferation and differentiation. The extrusion-based bioprinting of ASCs in GelNB/GelS-high was performed to manufacture three-dimensional cubic constructs. Results: All three hydrogels supported the viability, proliferation and chondrogenic differentiation of ASCs to a similar extent. The adipogenic differentiation of ASCs was better supported by the softer hydrogel (GelNB/GelS-low), whereas the osteogenic differentiation was more pronounced in the harder hydrogel (GelNB/GelS-high), indicating that the differentiation fate of ASCs can be influenced via the adaption of the mechanical properties of the GelNB/GelS system. After the ex vivo chondrogenic differentiation and subcutaneous implantation of the bioprinted construct into immunocompromised mice, the production of negatively charged sulfated proteoglycans could be observed with only minimal inflammatory signs in the implanted material. Conclusions: Our results indicate that the GelNB/GelS hydrogels are very well suited for the bioprinting of ASCs and may represent attractive hydrogels for subsequent in vivo tissue engineering applications.

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Naficy, Sina, Hugh R. Brown, Joselito M. Razal, Geoffrey M. Spinks e Philip G. Whitten. "Progress Toward Robust Polymer Hydrogels". Australian Journal of Chemistry 64, n.º 8 (2011): 1007. http://dx.doi.org/10.1071/ch11156.

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In this review we highlight new developments in tough hydrogel materials in terms of their enhanced mechanical performance and their corresponding toughening mechanisms. These mechanically robust hydrogels have been developed over the past 10 years with many now showing mechanical properties comparable with those of natural tissues. By first reviewing the brittleness of conventional synthetic hydrogels, we introduce each new class of tough hydrogel: homogeneous gels, slip-link gels, double-network gels, nanocomposite gels and gels formed using poly-functional crosslinkers. In each case we provide a description of the fracture process that may be occurring. With the exception of double network gels where the enhanced toughness is quite well understood, these descriptions remain to be confirmed. We also introduce material property charts for conventional and tough synthetic hydrogels to illustrate the wide range of mechanical and swelling properties exhibited by these materials and to highlight links between these properties and the network topology. Finally, we provide some suggestions for further work particularly with regard to some unanswered questions and possible avenues for further enhancement of gel toughness.

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Bhuyan, Md Murshed, e Jae-Ho Jeong. "Gels/Hydrogels in Different Devices/Instruments—A Review". Gels 10, n.º 9 (23 de agosto de 2024): 548. http://dx.doi.org/10.3390/gels10090548.

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Owing to their physical and chemical properties and stimuli-responsive nature, gels and hydrogels play vital roles in diverse application fields. The three-dimensional polymeric network structure of hydrogels is considered an alternative to many materials, such as conductors, ordinary films, constituent components of machines and robots, etc. The most recent applications of gels are in different devices like sensors, actuators, flexible screens, touch panels, flexible storage, solar cells, batteries, and electronic skin. This review article addresses the devices where gels are used, the progress of research, the working mechanisms of hydrogels in those devices, and future prospects. Preparation methods are also important for obtaining a suitable hydrogel. This review discusses different methods of hydrogel preparation from the respective raw materials. Moreover, the mechanism by which gels act as a part of electronic devices is described.

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Shoukat, Hina, Fahad Pervaiz e Sobia Noreen. "Novel Crosslinking Methods to Design Hydrogels". Global Pharmaceutical Sciences Review I, n.º I (30 de dezembro de 2016): 1–5. http://dx.doi.org/10.31703/gpsr.2016(i-i).01.

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Hydrogels are presently under consideration as matrices for the controlled bioactive molecules delivery particularly proteins and for living cells encapsulation. For these applications, gels must undergo degradation under physiological conditions. This overview summarized and discussed the various physical and chemical crosslinking methods to design hydrogels that are biodegradable. Highly versatile method to prepare hydrogels with good mechanical stability is chemical crosslinking. However, the crosslinker employed can give undesirable reactions with the bioactive substances present in the hydrogel matrix and are often toxic. So, it required to be removed from the gels before application. Physically crosslinked gels can be developed to overcome these adverse effects. Distortion due to variations in environmental conditions like presence of solute particles, ionic strength, pH, temperature and stress are the major disadvantages of reversible gels

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Li, Peng, Nam Hoon Kim, Sambhu Bhadra e Joong Hee Lee. "Electroresponsive Property of Novel Poly(acrylate- acryloyloxyethyl trimethyl ammonium chloride)/Clay Nanocomposite Hydrogels". Advanced Materials Research 79-82 (agosto de 2009): 2263–66. http://dx.doi.org/10.4028/www.scientific.net/amr.79-82.2263.

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The poly(acrylate-acryloyloxyethyl trimethyl ammonium chloride)/clay nanocomposite hydrogels (poly(AAc-DAc)/clay NC gels) with different clay contents were prepared by using clay as a cross-linker. The hydrogel exhibited good electroresponsive property and excellent mechanical property. The hydrogels initially bent toward the cathode side followed by anode side under an electric field. Concentrations of NaCl solution, voltage of electric field and clay content of the hydrogels have significant effects on the electroresponsive property of the hydrogels. Clay exhibited two opposite effects on the electroresponsive property of NC gels.

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Gorantla, Srividya, Tejashree Waghule, Vamshi Krishna Rapalli, Prem Prakash Singh, Sunil Kumar Dubey, Ranendra Narayan Saha e Gautam Singhvi. "Advanced Hydrogels Based Drug Delivery Systems for Ophthalmic Delivery". Recent Patents on Drug Delivery & Formulation 13, n.º 4 (29 de abril de 2020): 291–300. http://dx.doi.org/10.2174/1872211314666200108094851.

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Hydrogels are aqueous gels composed of cross-linked networks of hydrophilic polymers. Stimuli-responsive based hydrogels have gained focus over the past 20 years for treating ophthalmic diseases. Different stimuli-responsive mechanisms are involved in forming polymer hydrogel networks, including change in temperature, pH, ions, and others including light, thrombin, pressure, antigen, and glucose-responsive. Incorporation of nanocarriers with these smart stimuli-responsive drug delivery systems that can extend the duration of action by increasing ocular bioavailability and reducing the dosing frequency. This review will focus on the hydrogel drug delivery systems highlighting the gelling mechanisms and emerging stimuli-responsive hydrogels from preformed gels, nanogels, and the role of advanced 3D printed hydrogels in vision-threatening diseases like age-related macular degeneration and retinitis pigmentosa. It also provides insight into the limitations of hydrogels along with the safety and biocompatibility of the hydrogel drug delivery systems.

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O’Connor, Naphtali A., Abdulhaq Syed, Madeline Wong, Josiah Hicks, Greisly Nunez, Andrei Jitianu, Zach Siler e Marnie Peterson. "Polydopamine Antioxidant Hydrogels for Wound Healing Applications". Gels 6, n.º 4 (31 de outubro de 2020): 39. http://dx.doi.org/10.3390/gels6040039.

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Antioxidants are known to improve the wound healing process and are researched as a therapeutic strategy to treat chronic wounds. Dopamine is a known neurotransmitter with antioxidant properties that can be polymerized to form polydopamine (PDA). Herein, polydopamine is demonstrated as an antioxidant biomaterial. In prior work, we developed methodology to prepare hydrogels by crosslinking polysaccharides with polyamines via epichlorohydrin and NaOH. Using this previously developed methodology, dextran hydrogels crosslinked with polydopamine were prepared. Darkening of the gels indicated the increasing incorporation of polydopamine within the hydrogels. In addition to basic pH, polydopamine can be formed by reaction with polyethylene imine (PEI), which results in PEI-PDA copolymer. Dextran was similarly crosslinked with the PEI-PDA copolymer and resulted in sturdier, darker gels, which had more polydopamine incorporated. Hydrogel morphology and strength were dependent on the feed ratios of dopamine. Antioxidant activity of polydopamine containing hydrogel was confirmed and shown to be dependent on the amount of dopamine used in hydrogel synthesis. Hydrogels with 0.5 dopamine to dextran feed ratio scavenged 78.8% of radicals in a 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) antioxidant assay while gels with no dopamine scavenged only 1.4% of radicals. An ex vivo wound healing assay showed considerable cell migration with the PEI-PDA containing hydrogel.

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Fallon, Halligan, Pezzoli, Geever e Higginbotham. "Synthesis and Characterisation of Novel Temperature and pH Sensitive Physically Cross-Linked Poly (N-vinylcaprolactam-co-itaconic Acid) Hydrogels for Drug Delivery". Gels 5, n.º 3 (29 de agosto de 2019): 41. http://dx.doi.org/10.3390/gels5030041.

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Previous studies involving poly N-vinylcaprolactam (PNVCL) and itaconic acid (IA) have synthesised the hydrogels with the presence of a solvent and a crosslinker, producing chemically crosslinked hydrogel systems. In this study, however, temperature sensitive PNVCL was physically crosslinked with a pH-sensitive comonomer IA through ultraviolet (UV) free-radical polymerization, without the presence of a solvent, to produce hydrogels with dual sensitivity. The attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy indicated successful polymerisation of the hydrogels. The temperature and pH sensitivity of the hydrogels was investigated. The lower critical solution temperature (LCST) of the gels was determined using the UV spectrometry and it was found that the incorporation of IA decreased the LCST. Rheology was conducted to investigate the mechanical and viscoelastic properties of the hydrogels, with results indicating IA that enhances the mechanical properties of the gels. Swelling studies were carried out at ~20 °C and 37 °C in different buffer solutions simulating the gastrointestinal tract (pH 2.2 and pH 6.8). In acidic conditions, the gels showed gradual increase in swelling while remaining structurally intact. While in basic conditions, the gels had a burst in swelling and began to gradually degrade after 30 min. Results were similar for drug release studies. Acetaminophen was incorporated into the hydrogels. Drug dissolution studies were carried out at 37 °C in pH 2.2 and pH 6.8. It was found that <20% of acetaminophen was released from the gels in pH 2.2, whereas the maximum drug released at pH 6.8 was 74%. Cytotoxicity studies also demonstrated the hydrogels to be highly biocompatible. These results indicate that physically crosslinked P(NVCL-IA) gels possess dual pH and temperature sensitive properties, which may be beneficial for biomedical applications such as drug delivery.

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Seida, Yoshimi, e Hideaki Tokuyama. "Hydrogel Adsorbents for the Removal of Hazardous Pollutants—Requirements and Available Functions as Adsorbent". Gels 8, n.º 4 (3 de abril de 2022): 220. http://dx.doi.org/10.3390/gels8040220.

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Over the last few decades, various adsorption functions of polymer hydrogels for the removal of hazardous pollutants have been developed. The performance of hydrogel adsorbents depends on the constituents of the gels and the functions produced by the polymer networks of the gels. Research on hydrogels utilizing the characteristic functions of polymer networks has increased over the last decade. The functions of polymer networks are key to the development of advanced adsorbents for the removal of various pollutants. No review has discussed hydrogel adsorbents from the perspective of the roles and functions of polymer networks in hydrogels. This paper briefly reviews the basic requirements of adsorbents and the general characteristics of hydrogels as adsorbents. Thereafter, hydrogels are reviewed on the basis of the roles and functions of the polymer networks in them for the removal of hazardous pollutants by introducing studies published over the last decade. The application of hydrogels as adsorbents for the removal of hazardous pollutants is discussed as well.

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Mais fontes

Teses / dissertações sobre o assunto "Gels and Hydrogels"

Vaculíková, Hana. "Hyaluronan hydrogels". Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2019. http://www.nusl.cz/ntk/nusl-401877.

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In this thesis there was preparation optimized for agarose-gelatin hydrogels with addition of various concentrations of low-molecular and high-molecular hyaluronan and than there were examined viscoelastic properties of them by rheological oscilation tests and high-resolution ultrasonic spektrometry. By rheology were measured values of elastic and viscous modulus for selected amplitude of strain, oscilation frequencies and temperatures. In the second method there were recorded values of ultrasonic velocities of samples at temperature scanning from 85 to 25 °C and from 25 to 85 °C in HR-US 102, which were compared with ultrasonic velocities measured at the temperature 27,0±0,5 °C by gel-modul HR-EX-SSC.

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Shukla, Pranav. "Inducing Liquid Evaporation with Hygroscopic Gels". Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/101555.

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Mammals secrete fluids from the sweat glands known as perspiration which helps in thermoregulation. However, sweat can interfere with vision, comfort, grip, and results in malodor due to bacterial action. To combat the aforementioned issues, antiperspirants are widely used personal hygiene products to stop the sweat by blocking the sweat glands. Typically, aluminum salts present in the antiperspirants dissolve in the sweat and create a temporary plug to cut the flow of sweat. However, there has been a long debate going on the safety concerns of aluminum-based antiperspirants. Although there is no concrete evidence to prove the carcinogenicity of aluminum, various studies have also shown that long exposure to aluminum can lead to breast cancer in women. Hence there is a potential need to find aluminum-free alternatives for antiperspirants. Consumers are also showing an increased demand for more natural cosmetic products. The current study presents a novel aluminum-free the hygroscopic gel which can potentially serve as an antiperspirant. A synthetic sweat duct has been developed to mimic the sweating behavior of humans and to test the synthesized gels. Hygroscopic materials readily absorb and/or adsorb water from a humid environment. The hygroscopic gel can cause long-range evaporation of water from the sweat leading to crystallization of minerals which can ultimately clog the sweat duct and prevent sweating.
Master of Science

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Park, Tae Gwan. "Immobilized biocatalysts in stimuli-sensitive hydrogels /". Thesis, Connect to this title online; UW restricted, 1990. http://hdl.handle.net/1773/8070.

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Rehab, M. M. A. M. "Preparation and characterization of copolymeric hydrogels". Thesis, University of Salford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381697.

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Gräfe, David. "Tetra-Responsive Grafted Hydrogels for Flow Control in Microfluidics". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-219926.

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Microfluidics covers the science of manipulating small quantities of fluids using microscale devices with great potential in analysis, multiplexing, automation and high-throughput screening. Compared to conventional systems, microfluidics benefits from miniaturization resulting in shortened time of experiments, decreased sample and reagent consumptions as well as reduced overall costs. For microfluidic devices where further weight and cost reduction is additionally required, stimuli-responsive hydrogels are particularly interesting materials since they can convert an environmental stimulus directly to mechanical work without any extra power source. Hydrogels are used as chemostats, micropumps, and chemo-mechanical valves in microfluidics. Existing studies about hydrogels for flow control reported on hydrogels responsive to only one stimulus, including temperature, pH value, and solvent. Combining temperature and pH stimuli within one material is an interesting approach, which allows internal as well as external flow control and broadens potential applications. Among the variety of temperature- and pH-responsive monomers, N-isopropylacrylamide (NiPAAm) and acrylic acid (AA) are considered as ideal building blocks to obtain a hydrogel with pronounced stimuli response. There are different architectures for realizing a temperature- and pH-responsive hydrogel with NiPAAm and AA (e.g. copolymer gels, interpenetrating polymer networks (IPNs), semi-IPNs, or graft copolymer gels). Each approach has its inherent benefits and disadvantages. Grafted hydrogels with a temperature-responsive backbone and pH-responsive graft chains are a promising architecture overcoming drawbacks of copolymer gels (loss of thermoresponsive behavior due to the comonomer), interpenetrating polymer networks (IPNs, difficult fabrication of structured particles via soft lithography), and semi-IPNs (leakage of penetrating polymer). However, studies about multi-responsive grafted hydrogels for flow control in microfluidics are comparatively rare and further research is needed to emphasize their real potential. For this reason, the overall aim of this work was the synthesis of temperature- and pH-responsive grafted hydrogels based on NiPAAm and AA for flow control in microfluidics. This required the synthesis of a pH-responsive macromonomer by RAFT polymerization. As a suitable chain transfer agent with a carboxylic acid group for an end-group functionalization, 2-(dodecyl-thiocarbonothioylthio)-2-methylpropionic (DTP) acid was employed. The approach towards the synthesis of the pH-responsive macromonomer based on two key steps: (i) attaching a functional group, which retains during RAFT polymerization, and (ii) conducting the RAFT polymerization to synthesize the pH-responsive macromonomer. In total, four functionalizations for the macromonomer were investigated, including allyl, unconjugated vinyl, acrylamide, and styrene. End-group analysis and solubility tests revealed that macromonomers with a styrene functionalization are suitable for the synthesis of graft copolymer gels. A series of grafted net-PNiPAAm-g-PAA-styrene hydrogels with a PNiPAAm backbone and PAA-styrene graft chains (Mn = 4200 g/mol, Mw/Mn = 1.6) were prepared and characterized. The main goal was to identify suitable stimuli for an application as a chemo-mechanical valve and to show reversibility of the swelling and shrinking process. Importantly, the temperature sensitivity should be retained, while a pH response needs to be introduced. Equilibrium swelling studies quantified with the response ratio revealed that a grafting density of PAA-styrene between 0.25 and 1 mol-% provides a suitable response towards temperature, pH, salt, and solvent. Furthermore, the swelling and shrinking process is highly reproducible over four consecutive cycles for all four stimuli. In order to evaluate the swelling kinetics of grafted net-PNiPAAm-g-PAA-styrene hydrogels, the collective diffusion model extended by a volume specific surface was applied. The determined cooperative diffusion coefficients of net-PNiPAAm-g-PAA-styrene indicated faster response time with increasing PAA-styrene content. Remarkably, net-PNiPAAm-g-PAA-styrene containing 1 mol-% PAA-styrene exhibited an accelerated swelling rate by a factor of 9 compared to pure net-PNiPAAm. Rheological analysis of net-PNiPAAm-g-PAA-styrene showed that an increasing graft density leads to decreasing mechanical stability. The photopolymerization experiments showed that the gelation time linearly increases with the grafting density. Grafted net-PNiPAAm-g-PAA-styrene hydrogels were tested in two fluidic setups for flow control. A straightforward fluidic platform was developed consisting of a fluid reservoir, an inlet channel, an actuator chamber and an outlet channel. The actuator chamber was filled with crushed hydrogel particles. Accordingly, the fluid flow was directed by the active resistance of the hydrogel particles in the actuator chamber (i.e. swelling degree) and allowed flow control by the local environmental conditions. Flow rate studies showed that the fluid flow throttles when the inlet channel was provided with a solution in which the hydrogel swells (pH 9 buffer solution at room temperature). In contrast, the hydrogel-based valve opens immediately when a solution was used in which the hydrogel collapses. The advantageous properties of net-PNiPAAm-g-PAA-styrene were highlighted by using pH, salt and solvent stimulus in one experiment. Remarkably, the opening and closing function was reversible over six consecutive cycles. As part of a collaboration project with the chair of polymeric microsystems within the Cluster of Excellence Center for Advancing Electronics Dresden (A. Richter and P. Frank), membrane assures hydraulic coupling in a chemo-fluidic membrane transistor (CFMT) and grafted net-PNiPAAm-g-PAA-styrene hydrogels were combined to emphasize the potential of both systems. Flow rate studies showed that 4 different stimuli can be used to control the opening and closing state of the CFMT. Multiple opening and closing cycles revealed no considerable changes in the valve function emphasizing a high potential for an application in microfluidics.

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Singh, Nishant. "Functional gels as microreactors". Doctoral thesis, Universitat Jaume I, 2016. http://hdl.handle.net/10803/397698.

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Functionalized Hydrogels upon self-assembly demonslrate enzyme like catalysis owing to the formatin of hydrophobic pockets, increased local concentration of the catalytic sites, pKa change, pH shift etc. Here we present such hydrogelators being able to demonstrate enhanced catalysis for a range of reactions such as aldol, mannich, ester hydrolysis, deacetalisation etc.
Hidrogelantes funcionalizados sobre autoensamblaje pueden demostrar como la catálisis enzimática mejorada basada en varios factores tales como bolsillos hidrofóbicos, cambio en pH, cambio en pKa, aumento en la concentración local de los sitios activos etc. Aquí presentamos tales tipos de hidrogelantes que son capaces de demostrar varios tipos de reacciones importantes como aldolica, Mannicli, hidrolisis, deactetalisation, etc.

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Mujeeb, Ayeesha. "Self-assembled octapeptide gels for cartilage repair". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/selfassembled-octapeptide-gels-for-cartilage-repair(ce161da3-4ce4-4d42-b0cc-6933fc6aa394).html.

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Molecular self-assembly provides a simple and efficient route of constructing well-defined nanostructures which may serve as extra cellular matrix (ECM) mimics. This work focuses on two specific octapeptides: FEFEFKFK and FEFKFEFK (F: phenylalanine, E: glutamic acid, K: lysine) with alternating charge distribution. The peptides were shown to self-assemble in solution and form β-sheet rich nanofibres which, above a critical gelation concentration (CGC), entangle to form self-supporting hydrogels. The fibre morphology of the hydrogels was analysed using TEM and Cryo-SEM illustrating the dense fibrillar network of nanometer size fibres. Oscillatory rheology results showed that the hydrogels possesses viscoelastic properties. By varying peptide concentration and type hydrogel stiffness, viscosity, water content, fibre density and other mechanical properties were tailored to control cell interactions and subsequent tissue growth. Bovine chondrocytes were used to assess the biocompatibility of these novel scaffolds over 21 days under 2D and 3D cell culture conditions, particularly looking into cell morphology, proliferation and matrix deposition. 2D culture resulted in cell viability and collagen type I deposition. In 3D culture, the mechanically stable gel was shown to support viability, retention of cell morphology and collagen type II deposition. Subsequently, the scaffold may serve as a template for cartilage repair. In addition, this research also focused on developing novel injectable scaffold design with in situ gelation properties to encapsulate chondrocytes for cell culture applications.

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Buerkle, Lauren Elizabeth. "Tailoring the Properties of Supramolecular Gels". Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1317946752.

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Gruberová, Eliška. "Gelace hydrofobizovaného hyaluronanu". Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-449414.

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This diploma thesis deals with hyaluronan modified by palmitoyl and its gelation. Gels were created from palmitoyl hyaluronan with molecular weight 216 kDa and degree of substitution 11 % in concentrations 15 and 20 g dm-3 in water and concentrations 10, 15, 20 g dm-3 in NaCl and TSB. Also gel from palmitoyl hyaluronan with molecular weight 35 kDa and degree of substitution 10 % in concentrations 20, 30 g dm-3 in NaCl was created. Gels were investigated concerning medical applications. Gels were rigid and had very good properties, which was confirmed by rheology. The physical properties (pH, water content) of gels and stability were investigated. On the grounds of the MTT test, three methods of cell incorporation were suggested. Gels are nontoxic, biocompatible, and biodegradable with nontoxic degradation products and that is why they are excellent aspirants for use in biomedicine.

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Le, blay Heiva. "Use of shear wave imaging to assess the mechanical and fracture behaviors of tough model gels". Electronic Thesis or Diss., Université Paris sciences et lettres, 2021. http://www.theses.fr/2021UPSLS096.

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Un hydrogel est un matériau mou, largement gonflé d’eau, rendu élastique via un réseau de chaînes de polymère. Un gel est intrinsèquement fragile. On peut remédier à cette fragilité grâce à l’ajout de liaisons sacrificielles dynamiques. L’ingénierie macromoléculaire a permis au XXIème siècle de formuler des gels à destination de la biologie afin de proposer des matériaux de synthèse tout en remédiant aux problèmes de biocompatibilité, à la compatibilité des interfaces tissu/matériau et des propriétés mécaniques dont le corps a besoin. Pourtant, la fracture de ces matériaux hautement déformables et parfois viscoélastiques reste un sujet mal compris et assez peu investigué expérimentalement. Le défi aujourd’hui est de mieux comprendre les mécanismes mis en jeu en pointe de fissure mais les techniques expérimentales qui permettent une approche locale et avec des cadences d’acquisition rapides sont limitées. Notre travail vise à développer une méthode innovante pour sonder la fracture des gels. L’eau étant leur principal composant, ces matériaux, comme les tissus biologiques, sont une excellente plateforme pour l’étude de la propagation d’ondes acoustiques, i.e. de cisaillement (S) ou de compression (P). Dans les matériaux composés principalement d’eau, les ondes de compression, typiquement les ultrasons, se propagent à environ 1500 m/s (vitesse des ondes P dans l’eau) alors que les ondes de cisaillement sont de l’ordre du m/s (entre environ 1-8 m/s) et leur vitesse augmente avec la rigidité du matériau. Il est donc possible de voir les ondes S se propager grâce à la différence de vitesse entre ces deux ondes. C’est le principe de l’élastographie par onde de cisaillement, technique d’imagerie utilisée dans cette étude pour comprendre la mécanique et la fracture des hydrogels.La fracture des gels a été étudiée localement en pointe de fissure de manière quasi-statique. Ensuite, les phénomènes physiques mis en jeu lors de la propagation d’une fissure ont été investigués grâce à l’imagerie ultrarapide.Il est important de comprendre comment la fracture se propage et s’il est possible de l’éviter ou de la stopper. Le but de tout matériel est d’éviter de casser et donc de résister à la propagation de fracture
A hydrogel is a soft material, largely swollen with water, made elastic via a network of polymer chains. A gel is inherently fragile. This brittleness can be overcome by adding dynamic sacrificial bonds. Macromolecular engineering of the 21st century has made possible the formulation of gels for use in biology in order to provide synthetic materials while addressing biocompatibility issues, tissue/material interface compatibility, and mechanical properties that the body requires. However, the fracture of these highly deformable and sometimes viscoelastic materials remains a poorly understood subject that has been little investigated experimentally. The challenge today is to better understand the mechanisms involved at the crack tip but the experimental techniques that allow a local approach and with fast acquisition rates are limited. Our work aims at developing an innovative method to probe the fracture of gels. Water being their main component, these materials, like biological tissues, are an excellent platform to study the propagation of acoustic waves, i.e. shear (S) or compression (P) waves. In materials composed mainly of water, compressional waves, typically ultrasound, propagate at about 1500 m/s (P-wave velocity in water) while shear waves are of the order of m/s (between about 1-8 m/s) and their velocity increases with the rigidity of the material. It is therefore possible to see the S waves propagating through the difference in speed between these two waves. This is the principle of shear wave elastography, an imaging technique used in this study to understand the mechanics and fracture of hydrogels.The gel fracture was studied locally at the crack tip in a quasi-static way. Then, the physical phenomena involved during crack propagation were investigated using ultrafast imaging.It is important to understand how the fracture propagates and if it is possible to avoid or stop it. The goal of any material is to avoid breaking and therefore to resist fracture propagation

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Livros sobre o assunto "Gels and Hydrogels"

Park, Kinam. Biodegradable hydrogels for drug delivery. Lancaster, PA: Technomic Pub., 1993.

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M, Ottenbrite Raphael, Huang Samuel J. 1937-, Park Kinam, American Chemical Society Meeting e American Chemical Society. Division of Polymer Chemistry. (Washington, D.C.), eds. Hydrogels and biodegradable polymers for bioapplications. Washington, D.C: American Chemical Society, 1996.

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Scott, Adams, Palaszewski Bryan e United States. National Aeronautics and Space Administration., eds. Nanoparticulate gellants for metallized gelled liquid hydrogen wth aluminum. [Washington, DC]: National Aeronautics and Space Administration, 1996.

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B, Sunkara H., e United States. National Aeronautics and Space Administration., eds. Design of intelligent mesoscale periodic array structures utilizing smart hydrogel. [Washington, D.C: National Aeronautics and Space Administration, 1996.

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Hydrogels in medicine and pharmacy. Boca Raton, Fla: CRC Press, 1986.

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Peppas, Nikolaos. Hydrogels in Medicine and Pharmacy: Fundamentals. CRC Press, 1987.

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Park, Kinam, Haesun Park e Waleed S. W. Shalaby. Biodegradable Hydrogels for Drug Delivery. Taylor & Francis Group, 1993.

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Park, Kinam, Haesun Park e Waleed S. W. Shalaby. Biodegradable Hydrogels for Drug Delivery. Taylor & Francis Group, 1993.

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Park, Kinam, Haesun Park e Waleed S. W. Shalaby. Biodegradable Hydrogels for Drug Delivery. Taylor & Francis Group, 1993.

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Gels Handbook : Fundamentals, Properties and ApplicationsVolume 1 : Fundamentals of Hydrogelsvolume 2 : Applications of Hydrogels in Regenerative Medicinevolume 3: Application of Hydrogels in Drug Delivery and Biosensing. World Scientific Publishing Co Pte Ltd, 2016.

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Capítulos de livros sobre o assunto "Gels and Hydrogels"

Brøndsted, Helle, e Jindřich Kopeček. "pH-Sensitive Hydrogels". In Polyelectrolyte Gels, 285–304. Washington, DC: American Chemical Society, 1992. http://dx.doi.org/10.1021/bk-1992-0480.ch017.

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Kong, Weiqing, Qingqing Dai, Cundian Gao, Junli Ren, Chuanfu Liu e Runcang Sun. "Hemicellulose-Based Hydrogels and Their Potential Application". In Polymer Gels, 87–127. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-10-6086-1_3.

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Osada, Yoshihito, Ryuzo Kawamura e Ken-Ichi Sano. "Biomimetic Functions of Synthetic Polymer Gels". In Hydrogels of Cytoskeletal Proteins, 73–79. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-27377-8_7.

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Gitsov, Ivan, Thomas Lys e Chao Zhu. "Amphiphilic Hydrogels with Highly Ordered Hydrophobic Dendritic Domains". In Polymer Gels, 218–32. Washington, DC: American Chemical Society, 2002. http://dx.doi.org/10.1021/bk-2002-0833.ch015.

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Dualeh, Abdulkadir J., e Carol A. Steiner. "Structure and Properties of Surfactant-Bridged Viscoelastic Hydrogels". In Polyelectrolyte Gels, 42–52. Washington, DC: American Chemical Society, 1992. http://dx.doi.org/10.1021/bk-1992-0480.ch003.

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Oppermann, W. "Swelling Behavior and Elastic Properties of Ionic Hydrogels". In Polyelectrolyte Gels, 159–70. Washington, DC: American Chemical Society, 1992. http://dx.doi.org/10.1021/bk-1992-0480.ch010.

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Dong, Liang Chang, e Allan S. Hoffman. "Thermally Reversible Hydrogels". In Reversible Polymeric Gels and Related Systems, 236–44. Washington, DC: American Chemical Society, 1987. http://dx.doi.org/10.1021/bk-1987-0350.ch016.

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Chau, Mokit, Shivanthi Easwari Sriskandha, Héloïse Thérien-Aubin e Eugenia Kumacheva. "Supramolecular Nanofibrillar Polymer Hydrogels". In Supramolecular Polymer Networks and Gels, 167–208. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-15404-6_5.

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Allcock, Harry R., e Archel Ambrosio. "Synthesis and Characterization of pH-Responsive Poly(organophosphazene) Hydrogels". In Polymer Gels, 82–101. Washington, DC: American Chemical Society, 2002. http://dx.doi.org/10.1021/bk-2002-0833.ch006.

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Pape, A. C. H., e Patricia Y. W. Dankers. "Supramolecular Hydrogels for Regenerative Medicine". In Supramolecular Polymer Networks and Gels, 253–79. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-15404-6_7.

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Trabalhos de conferências sobre o assunto "Gels and Hydrogels"

Morovati, Vahid, Mohammad Ali Saadat e Roozbeh Dargazany. "Modelling Stress Softening and Necking Phenomena in Double Network Hydrogels". In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-12253.

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Abstract Double network (DN) gels are three-dimensional polymer matrices formed by interpenetrating networks. In contrast to the conventional single-network gels, DN gels have significant toughness, which makes them a promising material for different biomedical and biological applications. However, DN gels show complicated inelastic behavior including the Mullins effect and necking instability. Despite extensive efforts on modelling different aspects of the damage process in gels, the micro-mechanical modelling of the mechanisms that lead to necking in DN gels remains to be a challenging task. Here, a constitutive model is proposed to understand and describe the mechanical behavior of DN gels based on statistical micro-mechanics of interpenetrating polymer networks. DN gels behavior is divided into three parts including pre-necking, necking, and hardening. The first network is dominant in the response of the gel in the pre-necking stage. The breakage of the first network to smaller network fractions (clusters) induces the stress softening observed in this stage. The interaction of both networks and the second network are also considered as main contributors to the response of gel in necking and hardening stages, respectively. The contribution of clusters decreases during the necking as the second network starts hardening. The numerical results of the proposed model are validated and compared by uni-axial cyclic tensile experimental data of DN gels.

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Geisler, Chris G., Ho-Lung Li, David M. Wootton, Peter I. Lelkes e Jack G. Zhou. "Soft Biomaterial Study for 3-D Tissue Scaffold Printing". In ASME 2010 International Manufacturing Science and Engineering Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/msec2010-34274.

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In 3-D scaffold printing, it is critical to find a material that is suitable for your printing method, printing speed, and ease of use. For a biomaterial to best suit solid freeform fabrication techniques, it must: 1) be a low-viscous solution before being printed, 2) involve easily joined on-substrate mixing to form a homogenous gel, 3) have a short solution to gel transition time, 4) be a mechanically strong gel, and 5) have an irreversible gelation processes. Ionic crosslinkable, photocrosslinkable, and thermo-sensitive hydrogels have all been investigated and found to not fully satisfy our every requirement for SFF printing. Ionic crosslinking hydrogels can gel rapidly but tend to involve additional steps for crosslinking like freeze drying, stirring, and shaking, while some form beads, not homogenous gels. Some photocrosslinkable hydrogels would not work due to the concern for viability of cells in initial gel layers receiving copious amount of UV light. Thermosensitive hydrogels meet most of the requirements except that they are reversible gels. A new type of gel that obtains the qualities of a photocrosslinkable and thermosensitive hydrogel satisfies every requirement. A PEG-PLGA-PEG thermosensitive triblock copolymer additionally crosslinked with photocrosslinkable Irgacure 2959 allows for quick transition from solution to gel with a post-processing step utilizing UV light would add additional crosslinks to the gel structure resulting in an irreversible hydrogel.

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Vicente, Adam, Zachary McCreery e Karen Chang Yan. "Printability of Hydrogels for Hydrogel Molding Based Microfluidic Device Fabrication". In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-11545.

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Abstract Microfabrication-free methods have been developed in recent years for fabricating microfluidic devices to enable the applications of microfluidic devices to a broader range. Our group has been working on developing a process for fabricating electrospun fiber embedded microfluidic devices by integrating hydrogel molding (HGM) and electrospinning (ES), and the feasibility of this integrated method has been demonstrated through our initial study. Recently, we have modified an extrusion based 3D printer kit to deposit hydrogels and form microchannels. Agarose has been used for our previous studies owning to its temperature dependent gelation. In this study, we examined the feasibility of using gelatin gel as an alternative material for hydrogel molding. Gel materials with various concentrations were examined via printability assessments; and optimal gel materials were identified. Upon completion of pattern printing, the samples were then encapsulated in polydimethylsiloxane (PDMS) and cured; formed microchannels were then characterized via micrographic image analysis. The results show that three gels, 2% w/v agarose gel, 7.5% w/v gelatin gel, and a mixture of 2% w/v agarose gel and 7.5% w/v gelatin gel (1:1 ratio), yield consistent printed patterns and form consistent microchannels subsequently.

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Haraguchi, Kazutoshi, e Toru Takehisa. "Novel Manufacturing Process of Nanocomposite Hydrogel For Bio-Applications". In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-80533.

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A novel class of nanocomposite hydrogels (NC gels) with a unique organic / inorganic network structure was synthesized by in-situ free-radical polymerization of N-isopropylacrylamide (NIPA) or N,N-dimethylacrylamide (DMAA) in the presence of inorganic clay (hectorite). Since NC gels are composed of a unique organic / inorganic network structure, which consists of exfoliated clay platelets uniformly dispersed in an aqueous medium with a number of flexible polymer chains linking them together, NC gels exhibit high transparency, high degrees of swelling, and superb mechanical properties with extraordinarily large deformations. Also, NC gels formed from thermo-sensitive polymers, e.g. PNIPA, exhibit rapid temperature-response in transparency and gel volume (de-swelling) at the lower critical solution temperature (LCST). All the properties of NC gels are very different from those of conventional, chemically-crosslinked hydrogels (OR gels). Here, we evaluated various properties of NC gels from a biomaterials point of view, such as mechanical toughness (capable of sewing), absorption (water and saline), purification and extraction, drying (effect of cover film), coexistence of absorption and drying, sterilization (by autoclave and γ-ray irradiation), preliminary implantation (implanted to rabbit intramuscularly) and blood compatibility. These results indicate that NC gels are promising as soft biomaterials with blood compatibility as well as high transparency, absorbing power and mechanical properties.

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Morovati, Vahid, e Roozbeh Dargazany. "Micro-Mechanical Modeling of the Stress Softening in Double-Network Hydrogels". In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-88252.

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While single network hydrogels show limited extensibility and low strength, double-network hydrogels benefit from significantly high stretchability and toughness due to their reinforcing mechanism of combining two soft and rigid networks. Here, a micro-mechanical model is developed to characterize the constitutive behavior of DN hydrogels in quasi-static large deformation. In particular, we focused on describing the permanent damage in DN gels under large deformations. Irreversible chain detachment and decomposition of the first network are explored as the underlying reasons for the nonlinear inelastic phenomenon. The proposed model enables us to describe the damage and the way it influences the micro-structure of the gel. The model is validated with uni-axial loading and unloading experiments of DN gels. The proposed model contains a few numbers of material constants and shows a good agreement with cyclic uni-axial test data.

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Thien, Austen, e Kishore Pochiraju. "Additive Manufacturing Techniques for Soft Electroactive Polymer Hydrogels Using a Customized 3D Printer". In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-72007.

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Electroactive polymers (EAP) have shown promise in producing significant and controllable linear displacement in slim and lightweight packages. EAPs allow for seamless integration and multi-functionality since they are actuated by a driving voltage that could be controlled by a microprocessor. Polyacrylamide (PAAM)/Polyacrylic acid (PAA) hydrogel EAPs are commonly chosen due to their low driving voltage, significant amount of displacement, and rapid manufacturing capabilities, as these gels can be 3D printed. To effectively extrude these gels in 3D printers, their viscosity, gelation time, shear thinning, and self-wettability must be characterized. In this research, ungelled solutions of PAAM are prepared and then strain-tested at temperatures from 60C to 80C and with 1–2 drops of TEMED catalyst to determine the gelation time that is optimal for 3D printing. Strain testing of ungelled PAAM solutions is also used to determine the shear thinning propertie of the gel. All strain testing is conducted using a rheometer with 25 mm diameter plates and an oven enclosure. A prototype extrusion system is designed and fabricated to be used for self-wettability testing of the gel. The process data will then be used in the design of a modified 3D printer to manufacture and test different configurations of these hydrogel actuators.

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Marks, William H., Sze C. Yang, George W. Dombi e Sujata K. Bhatia. "Carbon Nanobrushes Embedded Within Hydrogel Composites for Tissue Engineering". In ASME 2013 2nd Global Congress on NanoEngineering for Medicine and Biology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/nemb2013-93122.

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The objective of this work is to study the effect of carbon nanobrushes embedded within hydrogel composites on tissue engineering. The carbon nanobrushes, providing electrical conductivity to the hydrogels, influence the growth and proliferation of clinically relevant cell lines within the hydrogel composite. The composite is comprised of carbon nanobrushes embedded in a biocompatible poloxamer gel. This work assesses the ability of such composite gels to support the growth of tissue by studying fibroblasts and myoctes, which serve as indicators on the feasibility of this platform eventually serving as a matrix to stimulate wound closure and repair injured tissue. In such a model, fibroblasts and myocytes are seeded separately on the composite hydrogel and bathed in culture medium. The experimental model assesses the ability of fibroblasts and myocytes to grow into and adhere to the gel containing carbon nanobrushes. The work demonstrates that carbon nanobrushes can be dispersed within poloxamer gels, and that fibroblasts and myoctyes can proliferate within a poloxamer gel containing homogenously dispersed carbon nanobrushes. The work also examines the role of the carbon nanobrushes in altering the physical properties of the hydrogel composite. This work has relevance for tissue engineering and tissue regeneration in clinical medicine, with a focus on utilizing biomimetic and bioinspired materials, like the carbon nanobrushes, to enhance growth capabilities.

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Yao, Hai, e Weiyong Gu. "New Insight Into Deformation-Dependent Hydraulic Permeability of Hydrogels and Cartilage". In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32520.

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Hydrogels have numerous applications in biomedical engineering and biotechnology, such as in cellular and tissue engineering. The transient mechanical behavior of hydrogels is related to its interstitial fluid flow which is governed by hydraulic permeability. The hydraulic permeability of hydrogels and other hydrated soft tissues (e.g., cartilage and intervertebral disc) is deformation dependent [1–3]. Several empirical expressions for deformation-dependent permeability of cartilage have been proposed, in order to quantify the fluid flow within a gel or tissue under mechanical loading [1,2,4]. In this paper, we report a new approach to investigating deformation-dependent permeability of hydrogels. The objective of this study is to find a relationship between hydraulic permeability and tissue porosity (water content) for hydrogels, and in turn derive its deformation-dependent permeability. This study is important for understanding biological responses of cells to interstitial fluid flow in gels or in cartilage under mechanical loading.

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Drzewiecki, Kathryn, Ian Gaudet, Douglas Pike, Jonathan Branch, Vikas Nanda e David Shreiber. "Temperature Dependent Reversible Self Assembly of Methacrylated Collagen Gels". In ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14705.

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Hydrogel-based tissue engineering scaffolds can allow tissues to repair and regenerate by providing a 3D environment similar to soft tissue. Type I collagen has the ability to assemble into a fibrillar gel at physiological temperature and pH, while promoting cell adhesion and growth. Our lab has modified type I collagen by covalently adding methacrylate groups to lysine residues to create collagen methacrylamide (CMA). This biomaterial, like collagen, maintains the ability to self-assemble, and can then be photocrosslinked with long-wave UV light and a water-soluble photoinitiator, which allows extensive spatiotemporal control of mechanical and biochemical properties [1]. In characterizing CMA and developing it for other applications, we discovered an interesting property. Unlike type I collagen hydrogels, which maintain a stable fibrillar network during cooling and freezing, CMA will spontaneously disassemble at temperatures less than 10°C. In this paper, we discuss the temperature-dependent rheological properties of CMA as well as the nature of its molecular and supramolecular structure in comparison to collagen.

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Earnshaw, Audrey L., Justine J. Roberts, Garret D. Nicodemus, Stephanie J. Bryant e Virginia L. Ferguson. "The Mechanical Behavior of Engineered Hydrogels". In ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-206705.

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Agarose and poly(ethylene-glycol) (PEG) are commonly used as scaffolds for cell and tissue engineering applications [1]. Agarose is a natural biomaterial that is thought to be inert [2] and permits growing cells and tissues in a three-dimensional suspension [3]. Gels synthesized from photoreactive poly(ethylene glycol) (PEG) macromonomers are well suited as cell carriers because they can be rapidly photopolymerized in vivo by a chain radical polymerization that is not toxic to cells, including chondrocytes. This paper explores the differences in mechanical behavior between agarose, a physically cross-linked hydrogel, and PEG, a chemically cross-linked hydrogel, to set the foundation for choosing hydrogel properties and chemistries for a desired tissue engineering application.

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Relatórios de organizações sobre o assunto "Gels and Hydrogels"

Benicewicz, Brian C., Glenn A. Eisman, S. K. Kumar e S. G. Greenbaum. Sol-Gel Based Polybenzimidazole Membranes for Hydrogen Pumping Devices. Office of Scientific and Technical Information (OSTI), fevereiro de 2014. http://dx.doi.org/10.2172/1121336.

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