| 1. |
- Fu, Yifeng, 1984, et al.
(författare)
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A complete carbon-nanotube-based on-chip cooling solution with very high heat dissipation capacity
- 2012
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Ingår i: Nanotechnology. - : IOP Publishing. - 1361-6528 .- 0957-4484. ; 23:4
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Tidskriftsartikel (refereegranskat)abstract
- Heat dissipation is one of the factors limiting the continuous miniaturization of electronics. In the study presented in this paper, we designed an ultra-thin heat sink using carbon nanotubes (CNTs) as micro cooling fins attached directly onto a chip. A metal-enhanced CNT transfer technique was utilized to improve the interface between the CNTs and the chip surface by minimizing the thermal contact resistance and promoting the mechanical strength of the microfins. In order to optimize the geometrical design of the CNT microfin structure, multi-scale modeling was performed. A molecular dynamics simulation (MDS) was carried out to investigate the interaction between water and CNTs at the nanoscale and a finite element method (FEM) modeling was executed to analyze the fluid field and temperature distribution at the macroscale. Experimental results show that water is much more efficient than air as a cooling medium due to its three orders-of-magnitude higher heat capacity. For a hotspot with a high power density of 5000 W cm(-2), the CNT microfins can cool down its temperature by more than 40 degrees C. The large heat dissipation capacity could make this cooling solution meet the thermal management requirement of the hottest electronic systems up to date.
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| 2. |
- Zhang, L., et al.
(författare)
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Study on the adhesion strength of new nano-structured polymer-metal composite for thermal interface material (Nano-TIM) under different pressures
- 2011
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Ingår i: Proceedings - 12th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2011, Shanghai, 8-11 August 2011. - 9781457717680 ; , s. 426-429
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Konferensbidrag (refereegranskat)abstract
- With the continual increase in cooling demand for microprocessors, the microelectronics industry has been increasingly focused on the development of thermal solutions. Thermal Interface Material (TIM) plays a key role in reducing the thermal resistance of packaging and the thermal resistance between the electronic device and the external cooling components. Nano-TIM, a new type of thermal interface material, was developed to improve the heat dissipation of electronic devices. This paper describes work undertaken to research the reliability of Nano-TIM. Pull tests were used to investigate the shear strength of samples with Nano-TIM of different thicknesses coalesced between two PCBs with Sn coating made under different pressure. Scanning Electron Microscopy (SEM) analysis techniques were used to determine the morphology of the shear fracture section after pull tests and observe the structure of the cross section of Nano-TIM coalesced between two PCBs with Sn coating.
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| 3. |
- Carlberg, Björn, 1983, et al.
(författare)
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Direct Photolithographic Patterning of Electrospun Films for Defined Nanofibrillar Microarchitectures
- 2010
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 26:4, s. 2235-2239
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, a method of generating spatially defined electrospun microarchitectures by direct photolithographic patterning of electrospun Films is described, A photoinitiator, benzoin methyl ether, is incorporated into a solid thermoplastic electrospun polyurethane matrix selectively photo-cross-linked by standard photolithographic methods. Subsequent development in in organic solvent yields spatially defined electrospun microstructures oil a single substrate. Utilizing a multilayer approach, the method allows for the assembly of complex hierarchical electrospun structures on single substrates using methods analogous to the conventional microfabrication of solid-state devices.
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| 4. |
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| 5. |
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| 6. |
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| 7. |
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| 8. |
- Fu, Yifeng, 1984, et al.
(författare)
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Templated Growth of Covalently Bonded Three-Dimensional Carbon Nanotube Networks Originated from Graphene
- 2012
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 24:12, s. 1576-1581
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Tidskriftsartikel (refereegranskat)abstract
- A template-assisted method that enables the growth of covalently bonded three-dimensional carbon nanotubes (CNTs) originating from graphene at a large scale is demonstrated. Atomic force microscopy-based mechanical tests show that the covalently bonded CNT structure can effectively distribute external loading throughout the network to improve the mechanical strength of the material.
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| 9. |
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| 10. |
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| 11. |
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| 12. |
- Liu, Johan, 1960, et al.
(författare)
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Stem Cell Growth and Migration on Nanofibrous Polymer Scaffolds and Micro-Fluidic Channels on Silicon-Chip
- 2009
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Ingår i: Proceedings of the 2009 Electronic Components and Technology Conference. - 0569-5503. - 9781424444762 ; , s. 1080-1085
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Konferensbidrag (refereegranskat)abstract
- Stem cell growth and migration on nanofibrous scaffolds and micro-fluidic channels on Silicon-Chip were studied by using neural stem cells isolated from adult rats' brain. Electrospinning and lithographic technique were used for developing nanofibrous-polylactic acid (PLA) and polyurethane (PU) based-scaffolds and micro-fluidic channels on Si-Chips respectively. Immunocytochemical and morphological analysis showed better cell-matrix interaction with profound adhesion, proliferation and migration on the developed scaffolds. Cell culture assay with microfluidic channel revealed the ability of developed channel system in guiding neuronal stem cell growth towards specified directions. These studies extend the possibility of using developed nanofibrous scaffolds and micro-fluidic channel system for future electrical signal transmission based on living neural stem cells.
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| 13. |
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| 14. |
- Wang, Teng, 1983, et al.
(författare)
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Low temperature transfer and formation of carbon nanotube arrays by imprinted conductive adhesive
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 91:9
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Tidskriftsartikel (refereegranskat)abstract
- This letter demonstrates the transfer and formation of aligned carbon nanotube (CNT) arrays at low temperature by imprinted conductive adhesive. A thermoplastic isotropic conductive adhesive is patterned by an imprint and heat transfer process. The CNTs grown by thermal chemical vapor deposition are then transferred to another substrate by the conductive adhesive, forming predefined patterns. The current-voltage response of the transferred CNT bundles verifies that good electrical connection has been established. This process can enable the integration of CNTs into various temperature-sensitive processeses and materials.
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| 15. |
- Carlberg, Björn, 1983, et al.
(författare)
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Electrospun polyurethane scaffolds for proliferation and neuronal differentiation of human embryonic stem cells.
- 2009
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Ingår i: Biomedical materials (Bristol, England). - : IOP Publishing. - 1748-605X .- 1748-6041. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- Adult central nervous system (CNS) tissue has a limited capacity to recover after trauma or disease. Hence, tissue engineering scaffolds intended for CNS repair and rehabilitation have been subject to intense research effort. Electrospun porous scaffolds, mimicking the natural three-dimensional environment of the in vivo extracellular matrix (ECM) and providing physical support, have been identified as promising candidates for CNS tissue engineering. The present study demonstrates in vitro culturing and neuronal differentiation of human embryonic stem cells (hESCs) on electrospun fibrous polyurethane scaffolds. Electrospun scaffolds composed of biocompatible polyurethane resin (Desmopan 9370A, Bayer MaterialScience AG) were prepared with a vertical electrospinning setup. Resulting scaffolds, with a thickness of approximately 150 microm, exhibited high porosity (84%) and a bimodal pore size distribution with peaks at 5-6 and 1 microm. The mean fiber diameter was measured to approximately 360 nm with a standard deviation of 80 nm. The undifferentiated hESC line SA002 (Cellartis AB, Göteborg, Sweden) was seeded and cultured on the produced scaffolds and allowed propagation and then differentiation for up to 47 days. Cultivation of hESC on electrospun fibrous scaffolds proved successful and neuronal differentiation was observed via standard immunocytochemistry. The results indicate that predominantly dopaminergic tyrosine hydroxylase (TH) positive neurons are derived in co-culture with fibrous scaffolds, in comparison to reference cultures under the same differentiation conditions displaying large proportions of GFAP positive cell types. Scanning electron micrographs confirm neurite outgrowth and connection to adjacent cells, as well as cell attachment to individual fibers of the fibrous scaffold. Consequently, electrospun polyurethane scaffolds have been proven feasible as a substrate for hESC propagation and neuronal differentiation. The physical interaction between cells and the fibrous scaffold indicates that these scaffolds provide a three-dimensional physical structure; a potential candidate for neural tissue engineering repair and rehabilitation.
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| 16. |
- Carlberg, Björn, 1983
(författare)
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Integration of Electrospun Materials in Microelectronic and Biomedical Applications
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis demonstrates the use of electrospinning and the novel properties of electrospunmaterials in two fields.The microelectronics industry has identified thermal interface materials as one of themajor bottlenecks hindering further integration at packaging level. New concepts basedon metal-polymer composite architectures are needed to fulfill current and future thermaland thermomechanical requirements on thermal interface materials at maintained costefficiency. In this thesis, an interpenetrating phase polymer-metal composite for thermalinterface material applications has been developed and characterized. Both fabricationand metrology equipment has been developed for the purpose at hand. The composite isbased on a porous electrospun polymer carrier infiltrated with a high thermal conductivitymetal phase. The two phases form two fully interpenetrating networks in the composite.Efficient heat transfer is achieved through the continuous metal phase, while the polymericphase defines geometry and phase composition. The devised composite architecture is believedto be a step towards meeting current and future demands on thermal performanceand thermomechanical reliability in microelectronic products.Furthermore, the thesis presents initial results of human embryonic stem cell proliferationand neural differentiation in co-culture with electrospun scaffolds, of interestin future regenerative medicine based on stem cells. Results indicate that physical cuesemanating from cell-scaffold interactions affect cells towards a neuronal fate during differentiation,a phenomenon consistent with reports in literature on physical cues influencingstem cell fate. To allow for deeper analysis on cell-scaffold interactions of thetype described above, a microfabricated platform was developed for the purpose. A novelmethod for direct photolithographic micropatterning of electrospun polyurethane fibrousfilms over large surfaces has been devised. The method allows for assembly of complexelectrospun microstructures on single substrates via a multilayer approach involving multiplephotolithographic exposures, analogous to conventional photolithography in microfabricationof solid state devices. Indeed, this technique can find application in a variety ofapplications where it is beneficial to integrate micropatterned electrospun structures intomicrofabricated devices, in particular within biomedical engineering applications.
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| 17. |
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| 18. |
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| 19. |
- Carlberg, Björn, 1983, et al.
(författare)
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Polymer-metal nanofibrous composite for thermal management of microsystems
- 2012
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Ingår i: Materials Letters. - : Elsevier BV. - 1873-4979 .- 0167-577X. ; 75, s. 229-232
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, a composite structure based on a porous electrospun polyimide structure infiltrated with indium aimed at thermal interface material applications is presented. A porous nanofibrous structure was prepared by electrospinning of polyimide. An interfacial nanocomposite layer of silver nanoparticles partially or fully embedded in the polyimide matrix was synthesized on the fiber surfaces, followed by autocatalytic deposition of a uniform silver coating (using the interfacial layer as an anchored seed layer) serving as a reactive wetting layer for the infiltrating melt. The thermal performance of the composite was evaluated and the thermal conductivity was determined to be 27 W/mK, accompanied by low contact resistance of the metallurgical bond (
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| 20. |
- Carlberg, Björn, 1983, et al.
(författare)
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Polymer nanofiber based continuous metal phase composite for thermal management applications
- 2010
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Ingår i: 3rd Electronics System Integration Technology Conference, ESTC 2010; Berlin; Germany; 13 September 2010 through 16 September 2010. - 9781424485536 ; , s. Art. no. 5642950-
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Konferensbidrag (refereegranskat)abstract
- A new composite design approach for thermal interface materials is presented. A porous electro spun nanofiber network composed of temperature stable poly imide was infiltrated with liquid phase indium at a pressure of 30 MPa. The polymer phase defmes composition and geometry, while the continuous metal phase gives binding to surfaces and high thermal conductivity. The composite was characterized by assembly of tri-layer copper/TIM/copper sandwich structures and subsequent xenon flash measurements extracting the thermal properties of the intermediate TIM layer. The interfacial contact resistance was found to be 8 Kmm2/W and the thermal conductivity was 28 W/mK, indicating the potential for use in thermal management applications.
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| 21. |
- Carlberg, Björn, 1983, et al.
(författare)
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Surface-Confined Synthesis of Silver Nanoparticle Composite Coating on Electrospun Polyimide Nanofibers
- 2011
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 7:21, s. 3057-3066
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Tidskriftsartikel (refereegranskat)abstract
- A methodology for fabricating hierarchical nanostructures by surface-confined synthesis of silver nanoparticles on electrospun polyimide nanofibers is reported. Through surface-confined imide cleavage at the dianhydride domain via immersion in an aqueous KOH solution, potassium polyamate coatings of accurately defined thickness are formed (at a rate of 25 nm h(-1)). By utilizing the ion-exchange capability of the polyamate resin, silver ions are introduced through immersion in an aqueous AgNO(3) solution. Subsequent reduction of the metal ion species leads to the formation of nanoparticles at the fiber surface. Two modes of reduction, chemical and thermal, are investigated in the report, each leading to distinct morphologies of the nanoparticle coatings. Via thermal reduction, a composite surface layer consisting of monodisperse silver nanoparticles (average diameter 5.2 nm) embedded in a re-imidized polyimide matrix is achieved. In the case of chemical reduction, the reduction process occurs preferentially at the surface of the fiber, leading to the formation of silver nanoparticles anchored at the surface, though not embedded, in a polyamic acid matrix. By regulating the modification depth, control of the particle density on the fiber surface is established. In both reduction approaches, the polyimide nanofiber core exhibits maintained integrity.
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| 22. |
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| 23. |
- Liu, Johan, 1960, et al.
(författare)
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Nanofiber based composites for thermal management
- 2010
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Ingår i: International Microsystems, Packaging, Assembly and Circuits Technology (IMPACT) Conference.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 24. |
- Sun, Shuangxi, 1986, et al.
(författare)
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Dissipating Heat from Hot Spot Using a New Nano Thermal Interface Material
- 2012
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Ingår i: Proceedings of IEEE CPMT 2012 International Conference on Electronic Packaging Technology & High Density Packaging. - 9781467316804 ; :Article number 6474593, s. 171-176
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Konferensbidrag (refereegranskat)abstract
- The need for faster, smaller, more reliable and efficient products has resulted in increased heat generated in microelectronic components. Removal of the heat generated is an important issue in electronic packaging. Therefore, a novel Nano-Thermal Interface Material was developed to improve this. This paper aims at studying the thermal performance of the new nano-structured polymer-metal composite film (Nano-TIM) in application for dissipating around hot spots which exist in non-uniform power generation. Through semiconductor process and Micron-RTD principle, 5*5mm 2 thermal test chips were developed to serve as a heat source for detecting the heat dissipation effect of the Nano-TIM. T3Ster test system and IR Camera were used to measure partial thermal resistance of the 50 and 75 um Nano-TIM layer and study the spread of different hot spot positions in 10*10mm 2 power chip. We also studied the hot spot dissipation effect under different die attach areas with the Nano-TIM. According to the results of this study, this new class of Nano-TIM can meet the high requirements for hot spot dissipation of highly non-uniform power distribution in electronics packaging. © 2012 IEEE.
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| 25. |
- Sun, S., et al.
(författare)
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Thermal performance characterization of nano thermal interface materials after power cycling
- 2012
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Ingår i: Proceedings - Electronic Components and Technology Conference. - 0569-5503. - 9781467319669 ; , s. 1426-1430
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Konferensbidrag (refereegranskat)abstract
- The need for faster, smaller, and more reliable and efficient products has resulted in increase of heat generated in microelectronic components. The removal of the heat generated is an important issue in electronic packaging. A novel Nano-TIM was developed to improve the heat dissipation of electronics packaging. This paper aims at studying the heat dissipation performance of a new class of nano-structured polymer-metal composite film (Nano-TIM) after power cycling. The new Nano-TIM uses metal to provide continuous thermal pathways while using nano-polymer to control the elasticity of the TIM. Through semiconductor processing and RTD principle, chips including 5*5, 10*10, 20*20, 30*30 (mm 2), were developed to study different size's influence on heat dissipation effect of the Nano-TIM. Additional parameters studied include power effect. RTD is used respectively to measure the junction temperature, and then the R thJC (Junction-to-Case Thermal Resistance) is calculated afterwards. The Transient thermal resistances of the Nano-TIM were also tested by T3Ster method to further study heat dissipation effect of Nano-TIM. The morphologies and interaction between the Nano-TIM and chips were carefully studied using X-ray Scanning Microscope to analyze heat flow path. The result shows that Nano-TIMs can be used to 30 mm in chip length as the thermal interface material.
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| 26. |
- Wallin, Patric, 1985, et al.
(författare)
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A method to integrate patterned electrospun fibers with microfluidic systems to generate complex microenvironments for cell culture applications
- 2012
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Ingår i: Biomicrofluidics. - : AIP Publishing. - 1932-1058. ; 6:2
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Tidskriftsartikel (refereegranskat)abstract
- The properties of a cell's microenvironment are one of the main driving forces in cellular fate processes and phenotype expression in vivo. The ability to create controlled cell microenvironments in vitro becomes increasingly important for studying or controlling phenotype expression in tissue engineering and drug discovery applications. This includes the capability to modify material surface properties within well-defined liquid environments in cell culture systems. One successful approach to mimic extra cellular matrix is with porous electrospun polymer fiber scaffolds, while microfluidic networks have been shown to efficiently generate spatially and temporally defined liquid microenvironments. Here, a method to integrate electrospun fibers with microfluidic networks was developed in order to form complex cell microenvironments with the capability to vary relevant parameters. Spatially defined regions of electrospun fibers of both aligned and random orientation were patterned on glass substrates that were irreversibly bonded to microfluidic networks produced in poly-dimethyl-siloxane. Concentration gradients obtained in the fiber containing channels were characterized experimentally and compared with values obtained by computational fluid dynamic simulations. Velocity and shear stress profiles, as well as vortex formation, were calculated to evaluate the influence of fiber pads on fluidic properties. The suitability of the system to support cell attachment and growth was demonstrated with a fibroblast cell line. The potential of the platform was further verified by a functional investigation of neural stem cell alignment in response to orientation of electrospun fibers versus a microfluidic generated chemoattractant gradient of stromal cell-derived factor 1 alpha. The described method is a competitive strategy to create complex microenvironments in vitro that allow detailed studies on the interplay of topography, substrate surface properties, and soluble microenvironment on cellular fate processes.
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| 27. |
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| 28. |
- Wang, Nan, 1988, et al.
(författare)
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Reliability investigation of nano-enhanced thermal conductive adhesives
- 2012
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Ingår i: Proceedings of the IEEE Conference on Nanotechnology. - 1944-9399 .- 1944-9380. - 9781467321983
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Konferensbidrag (refereegranskat)abstract
- This paper deals with silver (Ag) coated silicon carbide nanoparticles (SiC@Ag NPs) for thermal conductive interconnect and die attach applications.
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| 29. |
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