<i>In situ</i> multiphase fluid experiments in hydrothermal carbon nanotubes

Gogotsi, Yury; Libera, Joseph A.; Güvenç-Yazicioglu, Almila; Megaridis, Constantine M.

doi:10.1063/1.1391228

Cited by 253 publications

(207 citation statements)

References 15 publications

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“…The pores of nanowire arrays also have a high capillary pressure; however, their relative impermeability compared to microscale wick structures must be carefully assessed in the design process. Further, while the hydrophilicity of NWs and CNTs with water has been reported in the literature [205,206], aligned arrays of nanotubes have also been shown to behave as superhydrophobic surfaces [207]. Hence, surfactants may be used for liquid conveying applications [208], or nanostructures may be functionalized for heat transfer applications via metallization [51], hydrochloric acid treatment [209], or ultraviolet excitation [210].…”

Section: Nanostructured Capillary Wicks For Vapor Chamber Applicationsmentioning

confidence: 98%

Recent Advances in Vapor Chamber Transport Characterization for High-Heat-Flux Applications

Weibel

Garimella

2013

Advances in Heat Transfer

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Owing to their high reliability, simplicity of manufacture, passive operation, and effective heat transport, flat heat pipes and vapor chambers are used extensively in the thermal management of electronic devices. The need for concurrent size, weight, and performance improvements in high-performance electronics systems, without resort to active liquid-cooling strategies, demands passive heat spreading technologies that can dissipate extremely high heat fluxes from small hot spots. In response to these daunting application-driven trends, a number of recent investigations have focused on the design, characterization, and fabrication of ultra-thin vapor chambers for proximate heat spreading away from these hot spots. The predominant transport mechanisms and operational limits have been found to be different under these conditions relative to conventional low-power heat pipes. Noteworthy advances in the fundamental understanding of evaporation and boiling from porous microstructures fed by capillary action, and improvements in vapor chamber characterization, modeling, design, and fabrication techniques are reviewed. Characterization of evaporation and boiling from idealized and realistic wick structures, observation of vapor formation regimes as a function of operating conditions, assessment of fluid dryout limitations, design of novel multi-scale and nanostructured wicks for enhanced transport, and incorporation of these high heat flux transport phenomena into device-level models are discussed. These recent developments have successfully extended the maximum operating heat flux limits of vapor chambers.2

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Section: Nanostructured Capillary Wicks For Vapor Chamber Applicationsmentioning

confidence: 98%

Recent Advances in Vapor Chamber Transport Characterization for High-Heat-Flux Applications

Weibel

Garimella

2013

Advances in Heat Transfer

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“…The hydrophilicity of NWs and CNTs with water has been widely reported in the literature [13,[17][18][19]. Sessile-drop experiments performed by Ebbesen [20] with water on a CNT bundle showed complete wetting of the capillary channels between nanotubes.…”

Section: Introductionmentioning

confidence: 98%

Assessment of Nanostructured Capillary Wicks for Passive Two-Phase Heat Transport

Ranjan

Garimella

Murthy

et al. 2011

Nanoscale and Microscale Thermophysical Engineering

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The major factors limiting the thermal performance of passive two-phase heat-spreading devices are the ability of the wick structures to transport liquid by means of capillary forces and the thermal resistance posed by the wicks. Nano-scale geometric enhancements to the wick structure, through the use of carbon nanotubes and metallic nanowires, promise to enhance the capillary transport while at the same time decreasing the thermal resistance due to their high intrinsic thermal conductivity. We analyze the performance of nanostructured wicks in heat-spreading applications. We report that the flow resistance of nanostructures constitutes a major barrier to § Author to whom correspondence should be addressed. Phone: +1 (765) 494-5621 2 their use as passive flow-conveying media, and identify geometrical parameters which yield high rates of thin-film evaporation while minimizing the flow resistance. The analysis shows that the use of nanostructures as the sole wicking element in a two-phase thermal spreader restricts its footprint area to a size of 4 cm 2 for heat flux inputs as low as 1 W/cm 2 due to the large flow resistance in the nanowick. To overcome nanowick flow resistance, we propose a nanostructureenhanced sintered particle wick microstructure which leads to a decrease in the wick thermal resistance by 14% relative to the corresponding wick with the same flow resistance and without nanostructures.

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“…Computer simulations suggest that carbon nanotubes accommodate rapid water (12)(13)(14) and proton (15) flow and take up nucleic acids (16), despite their highly restricted pore size and low polarity. Water filling of nanotubes (17,18), as well as the flow of an aqueous electrolyte through carbon nanotube membranes (11) and the transport of DNA (19) through a single carbon nanotube were also observed experimentally.…”

mentioning

confidence: 93%

Nucleic acid transport through carbon nanotube membranes

Yeh

Hummer

2004

Proc. Natl. Acad. Sci. U.S.A.

166

127

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We study the electrophoretic transport of single-stranded RNA molecules through 1.5-nm-wide pores of carbon nanotube membranes by molecular dynamics simulations. From Ϸ170 individual RNA translocation events analyzed at full atomic resolution of solvent, membrane, and RNA, we identify key factors in membrane transport of biopolymers. RNA entry into the nanotube pores is controlled by conformational dynamics, and exit by hydrophobic attachment of RNA bases to the pores. Without electric field, RNA remains hydrophobically trapped in the membrane despite large entropic and energetic penalties for confining charged polymers inside nonpolar pores. Differences in RNA conformational flexibility and hydrophobicity result in sequence-dependent rates of translocation, a prerequisite for nanoscale separation devices.B iopolymer translocation across membranes is essential in many important biological processes, such as gene expression and protein targeting. Electrostatic membrane potentials play a critical role in biopolymer transport, as demonstrated for the import of unfolded proteins into the mitochondrial matrix (1). Electrostatically driven membrane translocation is also increasingly used to measure the properties of single polymers (2-6). The blockage of ionic currents during electric-field-driven translocation of individual nucleic acid molecules through membrane-inserted ␣-hemolysin channels (7) was shown to depend on length, base composition, and sequence (2, 3), suggesting possible applications in ultrafast and single-molecule sequencing of nucleic acids. However, the transport of polymers through membrane-bound protein channels (2-6) is complicated by specific molecular interactions with the highly structured pores. Nonbiological membranes and pores (8, 9), such as carbon nanotubes assembled into hexagonally packed two-dimensional arrays (10, 11), provide simple, controllable, and potentially more robust systems to study fundamental aspects of membrane translocation. Computer simulations suggest that carbon nanotubes accommodate rapid water (12-14) and proton (15) flow and take up nucleic acids (16), despite their highly restricted pore size and low polarity. Water filling of nanotubes (17, 18), as well as the flow of an aqueous electrolyte through carbon nanotube membranes (11) and the transport of DNA (19) through a single carbon nanotube were also observed experimentally.Here, we report the results of all-atom molecular dynamics simulations of RNA translocation through carbon nanotube membranes in explicit solvent. These simulations allow us to study membrane translocation at atomic detail, extending earlier studies of coarse-grained polymer translocation models (20-23). By including detailed descriptions of water and ions, the simulations capture electrostatic and hydrophobic solvation effects on the translocation processes and permit a detailed study of sequence dependences. As we will show, hydrophobic interactions of the bases with the nanotube pores can transiently trap RNA at the pore walls. To analyze t...

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In situ multiphase fluid experiments in hydrothermal carbon nanotubes

Cited by 253 publications

References 15 publications

Recent Advances in Vapor Chamber Transport Characterization for High-Heat-Flux Applications

Recent Advances in Vapor Chamber Transport Characterization for High-Heat-Flux Applications

Assessment of Nanostructured Capillary Wicks for Passive Two-Phase Heat Transport

Nucleic acid transport through carbon nanotube membranes

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