共查询到20条相似文献,搜索用时 15 毫秒
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Beata Butruk Maciej Trzaskowski Tomasz Ciach 《Materials science & engineering. C, Materials for biological applications》2012,32(6):1601-1609
In this paper the authors present a simple method of coating polyurethane (PU) surface with poly(vinyl pirrolidone) (PVP) hydrogel. The hydrogel-coated materials were designed for use in biomedical applications, especially in blood-contacting devices. The coating is formed due to free radical macromolecular grafting–crosslinking. Polymer surface was first immersed in an organic solution containing radical source: cumene hydroperoxide (CHP) with an addition of a branching and anchoring agent: ethylene glycol dimethylacrylate (EGDMA). In the second step, the substrate was immersed in a water solution containing given concentration of PVP and Fe2+. The novelty of the process consists in the fact that free radicals are formed mostly at the polymer/solution interface, what assures high grafting efficiency together with the formation of covalent bonds between polymer substrate and modifying layer.The process was optimized for reagents concentrations. The coating properties: thickness and the swelling ratio were strongly influenced by CHP, Fe2+, PVP and EGMDA concentrations. The chemical composition of the surface analyzed with FTIR-ATR spectroscopy confirmed the presence of PVP coating. In vitro biocompatibility tests with L929 fibroblasts confirmed non-cytotoxicity of the coatings. Hydrogel coating significantly improved polyurethane hemocompatibility. Studies with human whole blood revealed that both, the platelet consumption and the level of platelet activation were as low as for negative control. 相似文献
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Nima Roohpour Jaroslaw M. Wasikiewicz Deepen Paul Pankaj Vadgama Ihtesham U. Rehman 《Journal of materials science. Materials in medicine》2009,20(9):1803-1814
Polymeric membranes have been used as interfaces between implantable devices and biological tissues to operate as a protective
barrier from water exchanging and to enhance biocompatibility. Polyurethanes have been used as biocompatible membranes for
decades. In this study, copolymers of polyether urethane (PEU) with polydimethylsiloxane (PDMS) were synthesised with the
goal of creating materials with low water permeability and high elasticity. PDMS was incorporated into polymer backbone as
a part of the soft segment during polyurethane synthesis and physical properties as well as water permeability of resulting
copolymer were studied in regard to PDMS content. Increase in PDMS content led to increase of microphase separation of the
copolymer and corresponding increase in elastic modulus. Surface energy of the polymer was decreased by incorporating PDMS
compared to unmodified PEU. PDMS in copolymer formed a hydrophobic surface which caused reduction in water permeability and
water uptake of the membranes. Thus, PDMS containing polyurethane with its potent water resistant properties demonstrated
a great promise for use as an implantable encapsulation material. 相似文献
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Jiang D Zhang M Huo Z Wang Q Liu J Yu Z Yang X Wang Y Zhang B Chen J Liu M 《Nanotechnology》2011,22(25):254009
The endurance of Si nanocrystal memory devices under Fowler-Nordheim program and erase (P/E) cycling is investigated. Both threshold voltage (V(th)) and subthreshold swing (SS) degradation are observed when using a high program or erase voltage. The change of SS is found to be proportional to the shift of V(th), indicating that the generation of interface traps plays a dominant role. The charge pumping and the mid-gap voltage methods have been used to analyze endurance degradation both qualitatively and quantitatively. It is concluded that high erase voltage causes severe threshold voltage degradation by generating more interface traps and trapped oxide charges. 相似文献
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《Current Opinion in Solid State & Materials Science》2014,18(6):329-336
Implantable devices for recording and stimulation of the human nervous system offer promise for the treatment of disorders including spinal cord injury, stroke, traumatic brain injury, sensory and motor deficits, chronic pain, epilepsy, Parkinson’s disease and amputation. While advances in neuroengineering devices have been impressive, often the expectations and desires for a chronically implantable device remain unrealized. In the face of engineering approaches which perform well on the bench or in acute implantations is an immune response which is well-tuned to recognize foreign bodies, including the materials chosen for our innovations. Recent years have demonstrated a co-evolution of engineering solutions for neural disorders and knowledge of underlying biological hurdles. This review describes the state-of-the-art for implantable neuroengineering devices used for electrical recording and stimulation, the tissue response to these devices, and emerging technologies and materials to mitigate the tissue response. The test methods for candidate materials and paths to the commercial market are briefly described. 相似文献
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Choosing animal-derived regenerative implantable medical devices based on tissue engineering technology as a research theme, this paper presents bibliometric analysis of relative literature from the mainland of China to understand such data as publication year and journal preference, authors' geographic location, research topics and core expertise to predict the research trends and provide an informed basis of decision making for researchers and clinicians. 相似文献
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In wireless communications, a sleep mode is commonly used to save power for mobile stations (MS). When there is no traffic to transmit, an MS periodically switches to sleep mode. Obviously, the performance of a power-saving mechanism depends on its sleep mode scheduling algorithm and the traffic characteristics of the user. In real systems, the power-saving mechanism of IEEE802.11 WLAN uses a constant sleep interval, and the IEEE802.16e WMAN adopts one with truncated exponentially extending sleep intervals denoted by PS-16, which contains constant sleep intervals as special cases. The two mechanisms are compared, resulting in the, finding that in the case of Poisson traffic, they have the same performance; whereas in the case of non-Poisson traffic PS-16 has better performance. For non-Poisson traffic, the performance of PS-16 lacks a closed form expression, which makes its design challenging. The authors propose to approximate the idle durations of an MS by hyper-exponentials, based on which an online sleep mode scheduling algorithm is developed. Numerical examples are provided to illustrate the efficiency of the proposed algorithm. 相似文献
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DONG SUP LEE SU JIN KIM EUN BI KWON CHEOL WHEE PARK SU MIN JUN BUMKYOO CHOI SAE WOONG KIM 《Bulletin of Materials Science》2013,36(6):1127-1132
Implantable devices are often composed of or coated with different biologically compatible materials based on their requirements. Selecting a surface material for an implantable device is not an easy task, and it is necessary to compare the biocompatibilities of the available surface materials. In this study, we perform a comparison of the in vivo biocompatibilities of polydimethylsiloxane (PDMS) and para-xylyene polymer (parylene-C) as they are considered to be candidates for a coating material for implantable microelectronic devices. For in vivo biocompatibility testing, fifty four male Sprague-Dawley rats were used for testing, and they were divided into three groups (PDMS, parylene-C and a positive control). At one, four and twelve weeks after implantation of the test object, the density of inflammatory cells and the granulation layer thickness were recorded for each group and compared with other groups using visible light and fluorescence microscopy. The thickness of the granulation layer tended to decrease over time for all of the experimental groups, whereas the granulation layer thickness remained constant in the positive control group. The thinnest capsular layer was observed for the parylene-C group and fewest inflammatory cells were observed in this group during the entire experimental period. Macrophage infiltration was minimal, even at one week, and was not observed thereafter. The parylene-C group showed better biocompatibility than the PDMS groups, both for acute and chronic implantation. Thus, parylene-C is the best candidate of the tested materials for applications involving permanent implantable micro-devices. 相似文献
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In this paper we investigated atomic layer deposition (ALD) TiO2 thin films deposited on implantable neuro-chips based on electrolyte-oxide-semiconductor (EOS) junctions, implementing both efficient capacitive neuron-silicon coupling and biocompatibility for long-term implantable functionality.The ALD process was performed at 295 °C using titanium tetraisopropoxide and ozone as precursors on needle-shaped silicon substrates. Engineering of the capacitance of the EOS junctions introducing a thin Al2O3 buffer layer between TiO2 and silicon resulted in a further increase of the specific capacitance. Biocompatibility for long-term implantable neuroprosthetic systems was checked upon in-vitro treatment. 相似文献
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Sharareh Taghipour Dragan Banjevic Andrew K. S. Jardine 《Quality and Reliability Engineering International》2011,27(1):71-84
This paper proposes a method to analyze statistically maintenance data for complex medical devices with censoring and missing information. It presents a classification of the different types of failures and establishes policies for analyzing data at the system and component levels taking into account the failure types. The results of this analysis can be used as basic assumptions in the development of a maintenance/inspection optimization model. As a case study, we present the reliability analysis of a general infusion pump from a hospital. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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新型医用无镍不锈钢性能研究 总被引:4,自引:0,他引:4
医用植入不锈钢由于其优良的性能广泛应用于医疗领域,其中含有的镍元素由于腐蚀溶出除了对人体产生过敏反应外,还存在致畸、致癌的危害性.医用无镍不锈钢的研究和开发将会避免镍的危害,大大提高生物植入材料的长期使用安全性.本文总结了国内外医用无镍不锈钢的研究进展,并开展了新型医用无镍不锈钢(bioss4合金)的研究工作.与传统使用的医用316L不锈钢相比,新型医用无镍不锈钢具有更好的强韧性配合,优良的耐蚀性和生物学相容性,这种优势将为其提供了广阔的应用前景. 相似文献
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Pinto FC Da Silva-Cunha Junior A Oréfice RL Ayres E Andrade SP Lima LD Moura SA Da Silva GR 《Journal of materials science. Materials in medicine》2012,23(6):1431-1445
The purpose of this study was to develop triamcinolone acetonide-loaded polyurethane implants (TA PU implants) for the local treatment of different pathologies including arthritis, ocular and neuroinflammatory disorders. The TA PU implants were characterized by FTIR, SAXS and WAXS. The in vitro and in vivo release of TA from the PU implants was evaluated. The efficacy of TA PU implants in suppressing inflammatory-angiogenesis in a murine sponge model was demonstrated. FTIR results revealed no chemical interactions between polymer and drug. SAXS results indicated that the incorporation of the drug did not disturb the polymer morphology. WAXS showed that the crystalline nature of the TA was preserved after incorporation into the PU. The TA released from the PU implants efficiently inhibited the inflammatory-angiogenesis induced by sponge discs in an experimental animal model. Finally, TA PU implants could be used as local drug delivery systems because of their controlled delivery of TA. 相似文献
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Jeutter DC Josse F 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1993,40(5):469-477
Cochlear prosthesis systems for postlingually deaf individuals (those who have become deaf due to disease or injury after having developed mature speech capability) are considered. These systems require the surgical implantation of an array of electrodes within the cochlea and are driven by processed sound signals from outside the body. A system that uses an analog signal approach for transcutaneous transfer of six processed speech data channels using frequency multiplexing is described. The system utilizes a filterbank of six narrowband surface acoustic wave (SAW) filters in the range 72-78 MHz with a 1.2-MHz channel spacing to multiplex the six carrier signals, frequency modulated, by the processed speech signals, onto a composite signal. The same SAW filters are used in the receiver filterbank for signal separation, but are housed in a miniaturized package. The system includes a portable transmitter and a receiver package which is to be implanted in the patient. The implanted circuits are supplied exclusively from power transferred from outside the body via a separate 10-MHz transcutaneous link. 相似文献
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This paper examines a novel pressure drop mechanism as well as flow choking conditions that determine mass flow rate in refrigerant expansion devices. For this study, an ideal situation is considered where an expansion device such as a short tube orifice or a thermostatic expansion valve is modeled as an ideal isentropic nozzle. In addition, a liquid with a certain initial degree of superheat is first expanded in the converging nozzle down to the exit section without any phase transition. At the exit section where the metastable liquid jet flashes to produce a complex axisymmetric two-phase flow, a shock wave may terminate the overall expansion process. The model presented here is based on experimental observations in short nozzles, where the metastable liquid in the central core undergoes a sudden phase transition in the interfacial region, giving rise to a high-speed two-phase flow. A simple 1-D analysis of the radial evaporation wave based on the theory of discontinuities from gas dynamics leads to the Chapman–Jouguet (C-J) solution. Flow choking issues are examined and numerical examples are presented for three common refrigerants: R134a, R-22, and R-600a. Results suggest that the evaporation wave may be the flow controlling mechanism in these devices. 相似文献