The Experts below are selected from a list of 132 Experts worldwide ranked by ideXlab platform

Yingsong Yu - One of the best experts on this subject based on the ideXlab platform.

  • Evaporative Deposition of mono and bi dispersed colloids on a polydimethylsiloxane pdms surface
    Chemical Engineering Science, 2019
    Co-Authors: Yingsong Yu, Mingchao Wang, Jinzhi Zhou, An Zhou
    Abstract:

    Abstract Evaporative Deposition of mono- and bi-dispersed colloids on a polydimethylsiloxane (PDMS) surface was studied. At particle concentrations of 0.02 and 0.08 wt%, 1.58 μm diameter polystyrene (PS) microparticles were uniformly distributed from mono-dispersed colloids. PS microparticles located at the edge of the Deposition increased when the particle concentration increased to 0.32 and 1.28 wt%. Mono-dispersed colloids of 1.21 μm silica microparticles produced a ring-like Deposition at particle concentrations ranging from 0.02 to 0.32 wt%. The width of the ring increased with increasing concentration and a mountain-like structure was produced at 1.28 wt%. The settling speed of 1.21 μm silica microparticles is 14 times greater than 1.58 μm PS microparticles resulting in easier settling of silica compared with PS microparticles. Experimental investigations show PS microparticles are dragged inward with the depinning contact line, and the outmost silica microparticles are pinned. The edge of the Depositions of bi-dispersed colloids were made up of smaller microparticles and larger microparticles were found far from the edge due to capillary force.

  • Author Correction: Evaporative Deposition of polystyrene microparticles on PDMS surface.
    Scientific Reports, 2018
    Co-Authors: Yingsong Yu, Mingchao Wang, Xianfu Huang
    Abstract:

    A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

  • Evaporative Deposition of polystyrene microparticles on pdms surface
    Scientific Reports, 2017
    Co-Authors: Yingsong Yu, Mingchao Wang, Xianfu Huang
    Abstract:

    Evaporation of water and ethanol/water droplets containing large polystyrene (PS) microparticles on polydimethylsiloxane (PDMS) surface was experimentally investigated. It is found that no matter with or without small addition of ethanol, a compact monolayer Deposition is formed for lower microparticle concentration while mountain-like Deposition for higher concentration. Since the more volatile compound (ethanol) evaporates more quickly than the less volatile compound (water), evaporation of ethanol/water mixture droplet exhibits different characteristics from pure water. When the concentration of microparticle is low, the contact radius of ethanol/water mixture droplet decreases throughout the whole process, while the contact angle increases at first to a maximum, then keeps almost constant, and finally decreases sharply. However, the evaporation of ethanol/water mixture droplet with higher concentration of microparticle behaviors more complex. The settling time of microparticles was estimated and its theoretical value agrees well with the experimental one. Moreover, a mechanism of self-pinning of microparticles was used to elucidate the Deposition behavior of microparticles, indicating that as the contact line is depinning, the liquid film covering the outmost microparticle becomes thicker and thicker, and the microparticles have to move spontaneously with the depinning contact line under the action of capillary force.

J A Forrest - One of the best experts on this subject based on the ideXlab platform.

  • The properties of free polymer surfaces and their influence on the glass transition temperature of thin polystyrene films
    The European Physical Journal E, 2004
    Co-Authors: James S Sharp, J. H. Teichroeb, J A Forrest
    Abstract:

    We present a detailed study of free polymer surfaces and their effects on the measured glass transition temperature ( T _g) of thin polystyrene (PS) films. Direct measurements of the near-surface properties of PS films are made by monitoring the embedding of 10 and 20 nm diameter gold spheres into the surface of spin-cast PS films. At a temperature T = 378 K ( > T _g), the embedding of the spheres is driven by geometrical considerations arising from the wetting of the gold spheres by the PS. At temperatures below T _g ( 363 K < T < 370 K ), both sets of spheres embed 3-4 nm into the PS films and stop. These studies suggest that a liquid-like surface layer exists in glassy PS films and also provide an estimate for the lower bound of the thickness of this layer of 3-4 nm. This qualitative idea is supported by a series of calculations based upon a previously developed theoretical model for the indentation of nanoscale spheres into linear viscoelastic materials. Comparing data with simulations shows that this surface layer has properties similar to those of a bulk sample of PS having a temperature of 374 K. Ellipsometric measurements of the T _g are also performed on thin spin-cast PS films with thicknesses in the range 8 nm < h < 290 nm . Measurements are performed on thin PS films that have been capped by thermally evaporating 5 nm thick metal (Au and Al) capping layers on top of the polymer. The measured T _g values (as well as polymer metal interface structure) in such samples depend on the metal used as the capping layer, and cast doubt on the general validity of using Evaporative Deposition to cover the free surface. We also prepared films that were capped by a new non-Evaporative procedure. These films were shown to have a T _g that is the same as that of bulk PS (370±1 K) for all film thicknesses measured (> 7 nm). The subsequent removal of the metal layer from these films was shown to restore a thickness-dependent T _g in these samples that was essentially the same as that observed for uncapped PS films. An estimate of the thickness of the liquid-like surface layer was also extracted from the ellipsometry measurements and was found to be 5±1 nm. The combined ellipsometry and embedding studies provide strong evidence for the existence of a liquid-like surface layer in thin glassy PS films. They show that the presence of the free surface is an important parameter in determining the existence of T _g reductions in thin PS films.

  • free surfaces cause reductions in the glass transition temperature of thin polystyrene films
    Physical Review Letters, 2003
    Co-Authors: James S Sharp, J A Forrest
    Abstract:

    The effect of free surfaces on the glass transition temperature (T g ) of thin polystyrene films was studied. Measurements were performed on films (8 nm < h < 290 nm) with one free surface and on films capped with a 5 nm thick metal layer (no free surfaces). Potential problems with Evaporative Deposition were eliminated by studying samples made of two supported films placed with their free surfaces in contact and annealed. Uncapped films displayed reduced T g values for h ≤ 40 nm while all "properly" capped films exhibited a T g value the same as that of the bulk polymer (370 ′ 1 K). When the free surface was restored, the measured T g values the same as those of uncapped films of the same thickness. These results show that free surfaces are crucial for observing T g reductions in thin polymer films and address the role of the sample preparation history.

Xianfu Huang - One of the best experts on this subject based on the ideXlab platform.

  • Author Correction: Evaporative Deposition of polystyrene microparticles on PDMS surface.
    Scientific Reports, 2018
    Co-Authors: Yingsong Yu, Mingchao Wang, Xianfu Huang
    Abstract:

    A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

  • Evaporative Deposition of polystyrene microparticles on pdms surface
    Scientific Reports, 2017
    Co-Authors: Yingsong Yu, Mingchao Wang, Xianfu Huang
    Abstract:

    Evaporation of water and ethanol/water droplets containing large polystyrene (PS) microparticles on polydimethylsiloxane (PDMS) surface was experimentally investigated. It is found that no matter with or without small addition of ethanol, a compact monolayer Deposition is formed for lower microparticle concentration while mountain-like Deposition for higher concentration. Since the more volatile compound (ethanol) evaporates more quickly than the less volatile compound (water), evaporation of ethanol/water mixture droplet exhibits different characteristics from pure water. When the concentration of microparticle is low, the contact radius of ethanol/water mixture droplet decreases throughout the whole process, while the contact angle increases at first to a maximum, then keeps almost constant, and finally decreases sharply. However, the evaporation of ethanol/water mixture droplet with higher concentration of microparticle behaviors more complex. The settling time of microparticles was estimated and its theoretical value agrees well with the experimental one. Moreover, a mechanism of self-pinning of microparticles was used to elucidate the Deposition behavior of microparticles, indicating that as the contact line is depinning, the liquid film covering the outmost microparticle becomes thicker and thicker, and the microparticles have to move spontaneously with the depinning contact line under the action of capillary force.

Mingchao Wang - One of the best experts on this subject based on the ideXlab platform.

  • Evaporative Deposition of mono and bi dispersed colloids on a polydimethylsiloxane pdms surface
    Chemical Engineering Science, 2019
    Co-Authors: Yingsong Yu, Mingchao Wang, Jinzhi Zhou, An Zhou
    Abstract:

    Abstract Evaporative Deposition of mono- and bi-dispersed colloids on a polydimethylsiloxane (PDMS) surface was studied. At particle concentrations of 0.02 and 0.08 wt%, 1.58 μm diameter polystyrene (PS) microparticles were uniformly distributed from mono-dispersed colloids. PS microparticles located at the edge of the Deposition increased when the particle concentration increased to 0.32 and 1.28 wt%. Mono-dispersed colloids of 1.21 μm silica microparticles produced a ring-like Deposition at particle concentrations ranging from 0.02 to 0.32 wt%. The width of the ring increased with increasing concentration and a mountain-like structure was produced at 1.28 wt%. The settling speed of 1.21 μm silica microparticles is 14 times greater than 1.58 μm PS microparticles resulting in easier settling of silica compared with PS microparticles. Experimental investigations show PS microparticles are dragged inward with the depinning contact line, and the outmost silica microparticles are pinned. The edge of the Depositions of bi-dispersed colloids were made up of smaller microparticles and larger microparticles were found far from the edge due to capillary force.

  • Author Correction: Evaporative Deposition of polystyrene microparticles on PDMS surface.
    Scientific Reports, 2018
    Co-Authors: Yingsong Yu, Mingchao Wang, Xianfu Huang
    Abstract:

    A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

  • Evaporative Deposition of polystyrene microparticles on pdms surface
    Scientific Reports, 2017
    Co-Authors: Yingsong Yu, Mingchao Wang, Xianfu Huang
    Abstract:

    Evaporation of water and ethanol/water droplets containing large polystyrene (PS) microparticles on polydimethylsiloxane (PDMS) surface was experimentally investigated. It is found that no matter with or without small addition of ethanol, a compact monolayer Deposition is formed for lower microparticle concentration while mountain-like Deposition for higher concentration. Since the more volatile compound (ethanol) evaporates more quickly than the less volatile compound (water), evaporation of ethanol/water mixture droplet exhibits different characteristics from pure water. When the concentration of microparticle is low, the contact radius of ethanol/water mixture droplet decreases throughout the whole process, while the contact angle increases at first to a maximum, then keeps almost constant, and finally decreases sharply. However, the evaporation of ethanol/water mixture droplet with higher concentration of microparticle behaviors more complex. The settling time of microparticles was estimated and its theoretical value agrees well with the experimental one. Moreover, a mechanism of self-pinning of microparticles was used to elucidate the Deposition behavior of microparticles, indicating that as the contact line is depinning, the liquid film covering the outmost microparticle becomes thicker and thicker, and the microparticles have to move spontaneously with the depinning contact line under the action of capillary force.

James S Sharp - One of the best experts on this subject based on the ideXlab platform.

  • The properties of free polymer surfaces and their influence on the glass transition temperature of thin polystyrene films
    The European Physical Journal E, 2004
    Co-Authors: James S Sharp, J. H. Teichroeb, J A Forrest
    Abstract:

    We present a detailed study of free polymer surfaces and their effects on the measured glass transition temperature ( T _g) of thin polystyrene (PS) films. Direct measurements of the near-surface properties of PS films are made by monitoring the embedding of 10 and 20 nm diameter gold spheres into the surface of spin-cast PS films. At a temperature T = 378 K ( > T _g), the embedding of the spheres is driven by geometrical considerations arising from the wetting of the gold spheres by the PS. At temperatures below T _g ( 363 K < T < 370 K ), both sets of spheres embed 3-4 nm into the PS films and stop. These studies suggest that a liquid-like surface layer exists in glassy PS films and also provide an estimate for the lower bound of the thickness of this layer of 3-4 nm. This qualitative idea is supported by a series of calculations based upon a previously developed theoretical model for the indentation of nanoscale spheres into linear viscoelastic materials. Comparing data with simulations shows that this surface layer has properties similar to those of a bulk sample of PS having a temperature of 374 K. Ellipsometric measurements of the T _g are also performed on thin spin-cast PS films with thicknesses in the range 8 nm < h < 290 nm . Measurements are performed on thin PS films that have been capped by thermally evaporating 5 nm thick metal (Au and Al) capping layers on top of the polymer. The measured T _g values (as well as polymer metal interface structure) in such samples depend on the metal used as the capping layer, and cast doubt on the general validity of using Evaporative Deposition to cover the free surface. We also prepared films that were capped by a new non-Evaporative procedure. These films were shown to have a T _g that is the same as that of bulk PS (370±1 K) for all film thicknesses measured (> 7 nm). The subsequent removal of the metal layer from these films was shown to restore a thickness-dependent T _g in these samples that was essentially the same as that observed for uncapped PS films. An estimate of the thickness of the liquid-like surface layer was also extracted from the ellipsometry measurements and was found to be 5±1 nm. The combined ellipsometry and embedding studies provide strong evidence for the existence of a liquid-like surface layer in thin glassy PS films. They show that the presence of the free surface is an important parameter in determining the existence of T _g reductions in thin PS films.

  • free surfaces cause reductions in the glass transition temperature of thin polystyrene films
    Physical Review Letters, 2003
    Co-Authors: James S Sharp, J A Forrest
    Abstract:

    The effect of free surfaces on the glass transition temperature (T g ) of thin polystyrene films was studied. Measurements were performed on films (8 nm < h < 290 nm) with one free surface and on films capped with a 5 nm thick metal layer (no free surfaces). Potential problems with Evaporative Deposition were eliminated by studying samples made of two supported films placed with their free surfaces in contact and annealed. Uncapped films displayed reduced T g values for h ≤ 40 nm while all "properly" capped films exhibited a T g value the same as that of the bulk polymer (370 ′ 1 K). When the free surface was restored, the measured T g values the same as those of uncapped films of the same thickness. These results show that free surfaces are crucial for observing T g reductions in thin polymer films and address the role of the sample preparation history.