| 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. |
- 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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| 3. |
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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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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| 9. |
- 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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