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254 results on '"Adamson, Douglas H."'

1. Long-Range Attraction between Graphene and Water/Oil Interfaces

Author

Abeywickrama, Avishi, Adamson, Douglas H., and Schniepp, Hannes C.

Subjects
Condensed Matter - Soft Condensed Matter, Condensed Matter - Materials Science
Abstract

We directly measured the interactions between a hydrophobic solid and a hydrophobic liquid separated by water using force spectroscopy, where colloidal probes were coated with graphene oxide (GO) to interact with immobilized heptane droplets in water. We detected attractions with a long range of ~0.5 microns, which cannot be readily explained by standard Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. When the GO was reduced to become more hydrophobic, these forces increased in strength and ranged up to 1.2 microns, suggesting that the hydrophobic nature of the involved surfaces critically influences the observed long-range forces. Previous studies have addressed such hydrophobic attractions, but were limited to solid/water/solid and solid/water/air scenarios. Here we expand this knowledge to include the solid/water/liquid situation. Based on our results, we propose air bubbles attached to the colloidal probe and molecular rearrangement at the water/oil interface as possible origins of the observed interactions. The proposed mechanism expands insights gained from previous to the solid/water/liquid situation and is universally applicable to describe attractive interactions between hydrophobic bodies of any kind separated by water. Our work will be useful to understand and motivate the formation of many colloid and interface phenomena, including emulsions using 2D materials and other amphiphilic/hydrophobic particles.

Published
2023

19. Mechanisms of Ordering in Striped Patterns

Author

Harrison, Christopher, Adamson, Douglas H., Cheng, Zhengdong, Sebastian, John M., Sethuraman, Srinivasan, Huse, David A., Register, Richard A., and Chaikin, P. M.

Published
2000

26. Fucntionalized single graphene sheets derived from splitting graphite oxide

Author

Schniepp, Hannes C., Je-Luen Li, McAllister, Michael J., Sai, Hiroaki, Herrera-Alonso, Margarita, Adamson, Douglas H., Prud'homme, Robert K., Car, Roberto, Saville, Dudley A., and Aksay, Ilhan A.

Subjects
Graphite -- Thermal properties, Oxidation-reduction reaction -- Research, Chemicals, plastics and rubber industries
Abstract

A process that produces single sheets of functionalized graphene through thermal exfoliation of graphite oxide is described. The process yields a wrinkled sheet structure resulting from reaction sites involved in oxidation and reduction processes.

Published
2006

36. Block copolymer lithography: periodic arrays of about 10 to the 11th power holes in 1 square centimeter

Author

Park, Miri, Harrison, Christopher, Chaikin, Paul M., Register, Richard A., and Adamson, Douglas H.

Subjects
Thin-film circuits -- Research, Miniature electronic equipment -- Research, Nanotechnology -- Research, Microelectronics -- Research, Science and technology, Research
Abstract

Dense periodic arrays of holes and dots have been fabricated in a silicon nitride-coated silicon wafer. The holes are 20 nanometers across, 40 nanometers apart, and hexagonally ordered with a polygrain structure that has an average grain size of 10 by 10. Spin-coated diblock copolymer thin films with well-ordered spherical or cylindrical microdomains were used as the templates. The microdomain patterns were transferred directly to the underlying silicon nitride layer by two complementary techniques that resulted in opposite tones of the patterns. This process opens a route for nanometer-scale surface patterning by means of spontaneous self-assembly in synthetic materials on length scales that are difficult to obtain by standard semiconductor lithography techniques., In general, feature sizes greater than 300 nm are routinely produced by photolithography techniques. For feature sizes between 300 and 30 nm, electron beam lithography is commonly used. However, feature [...]

Published
1997

37. Interfacial Strength and Physical Properties of Functionalized Graphene - Epoxy Nanocomposites

Author

Miller, Sandi G, Heimann, Paula, Scheiman, Daniel, Adamson, Douglas H, Aksay, Iihan A, and Prud'homme, Robert K

Subjects
Composite Materials
Abstract

The toughness and coefficient of thermal expansion of a series of functionalized graphene sheet - epoxy nanocomposites are investigated. Functionalized graphene sheets are produced by splitting graphite oxide into single graphene sheets through a rapid thermal expansion process. These graphene sheets contain approx. 10% oxygen due to the presence of hydroxide, epoxide, and carboxyl functional groups which assist in chemical bond formation with the epoxy matrix. Intrinsic surface functionality is used to graft alkyl amine chains on the graphene sheets, and the addition of excess hardener insures covalent bonding between the epoxide matrix and graphene sheets. Considerable improvement in the epoxy dimensional stability is obtained. An increase in nanocomposite toughness is observed in some cases.

Published
2006

42. Graphene and Poly(3,4-ethylene dioxythiophene):Poly(4-styrenesulfonate) on Nonwoven Fabric as a Room Temperature Metal and Its Application as Dry Electrodes for Electrocardiography

Author

Sinha, Sneh K., primary, Alamer, Fahad A., additional, Woltornist, Steven J., additional, Noh, Yeonsik, additional, Chen, Feiyang, additional, McDannald, Austin, additional, Allen, Christopher, additional, Daniels, Robert, additional, Deshmukh, Ajinkya, additional, Jain, Menka, additional, Chon, Ki, additional, Adamson, Douglas H., additional, and Sotzing, Gregory A., additional

Published
2019
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46. Silicon nanowire polarizers for far ultraviolet (sub-200 nm) applications: Modeling and fabrication.

Author

Papalia, John M., Adamson, Douglas H., Chaikin, Paul M., and Register, Richard A.

Subjects
*PHYSICS research, *SEMICONDUCTOR industry, *NANOWIRES, *POLARIZERS (Light), *POLYMERS, *BLOCK copolymers, *NANOSTRUCTURED materials, *PHOTOLITHOGRAPHY
Abstract

We have previously demonstrated a fabrication technique for the creation of silicon wire grid polarizers (WGPs) for far (deep) ultraviolet applications utilizing a shear-aligned cylinder-forming polystyrene-b-poly(n-hexyl methacrylate) diblock copolymer as a mask for reactive ion etching of an amorphous silicon substrate. In our current work, a numerical model is refined and applied to our experimental systems to describe the impact of wire height and periodicity, and tradeoffs between the two, on polarization efficiency. We focus our attention at a wavelength of 193 nm, the emission wavelength of the ArF excimer laser currently in use in advanced photolithographic processes. Through application of the model’s predictions we have achieved marked improvement in the polarization efficiency of our WGPs by increasing the block copolymer molecular weight, thereby increasing the thickness of the Si wires, which compensates for a simultaneous increase in wire periodicity; the resulting arrays of parallel Si nanowires exhibit polarization efficiencies approaching 64% at 193 nm, a 68% relative increase over our previous Si WGPs. [ABSTRACT FROM AUTHOR]

Published
2010
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50. Graphene and Poly(3,4-ethylene dioxythiophene):Poly(4-styrenesulfonate) on Nonwoven Fabric as a Room Temperature Metal and Its Application as Dry Electrodes for Electrocardiography

Author

Sinha, Sneh K., Alamer, Fahad A., Woltornist, Steven J., Noh, Yeonsik, Chen, Feiyang, McDannald, Austin, Allen, Christopher, Daniels, Robert, Deshmukh, Ajinkya, Jain, Menka, Chon, Ki, Adamson, Douglas H., and Sotzing, Gregory A.

Abstract

Highly conductive, metal-like poly(ethylene terephthalate) (PET) nonwoven fabric was prepared by coating poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) containing dimethyl sulfoxide (DMSO) onto PET nonwoven fabric previously coated with graphene/graphite. The sheet resistance of the original nonwoven fabric decreases from >80 MΩ□–1to 1.1 Ω□–1after coating with 10.7 wt % graphene and 5.48 wt % PEDOT:PSS with a maximum current at breakdown of 4 A. This sheet resistance is lower than previously reported sheet resistances of fabrics coated with graphene films, PEDOT:PSS films, or PEDOT:PSS coated fabrics from the literature. The effect of temperature on the resistance of graphene/PEDOT:PSS coated fabric has revealed that the resistance decreases with increasing temperature, analogous to semiconductors, with a clear semiconductor–metal transitionoccurring at 290 K. Finally, a coating of 18 wt % graphene/graphite and 2.5 wt % PEDOT:PSS (Rs= 5.5 Ω□–1) screen printed on the nonwoven fabric was shown to function as an electrode for electrocardiography without any hydrogel and with dry skin conditions. This composite coating finds application in wearable electronics for military and consumer sectors.

Published
2024
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