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Search Publications by: Christopher Stafford (Fed)

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Displaying 126 - 150 of 198

Effects of sample preparation on bacterial colonization of polymers

October 19, 2009
Author(s)
Diana N. Zeiger, Christopher Stafford, Yajun Cheng, Stefan D. Leigh, Sheng Lin-Gibson, Nancy Lin
Characterization of materials developed for medical usage frequently includes studies in which the materials are inoculated with bacteria in order to assess biofilm formation. Differences in the bacteria are considered to be due to the material alone; the

Viscoelastic Properties of Confined Polymer Films Measured via Thermal Wrinkling

October 8, 2009
Author(s)
Kirt A. Page, Edwin Chan, Se Hyuk Im, Derek L. Patton, Rui Huang, Christopher Stafford
We present a new measurement technique to quantify the viscoelastic properties of polymer thin films. This approach utilizes thermally-induced surface wrinkling to measure the rubbery modulus and shear viscosity of polymer thin films. Specifically, by

Microbial colonization on polymers: Effects of sample preparation and incorporation of quaternary ammonium salts

September 13, 2009
Author(s)
Nancy J. Lin, Diana N. Zeiger, Joseph M. Antonucci, Bruce O. Fowler, Christopher M. Stafford, Sheng Lin-Gibson
Controlling bacterial growth in the oral environment presents many challenges. To address these challenges, new materials and treatments are needed along with controlled, reproducible methods to evaluate their efficacy. In this study, a reproducible method

Adhesion and Mechanics of Complex Polymer Interfaces

August 16, 2009
Author(s)
Christopher M. Stafford, Jun Y. Chung, Heqing Huang, Adam J. Nolte, Peter M. Johnson, Edwin P. Chan
The structure and properties of polymer interfaces play an integral role in numerous technological applications, particularly in the areas of coatings and adhesives. These interfacial interactions are dependent on a host of factors, including interfacial

SERS not to be taken for granted in the presence of oxygen

May 15, 2009
Author(s)
Melek Erol, Yun Han, Scott K. Stanley, Christopher Stafford, Henry Du, Svetlana Sukhishvili
In this communication, we report that oxidation of the Ag nanoparticle (Ag NP) surface under ambient conditions has a dramatic effect on the adsorption and SERS detection limit of nitroaromatic molecules in aqueous solutions. We show for the first time

Low-temperature plasma assisted nanotransfer printing between thermoplastic polymers

March 26, 2009
Author(s)
Deuk Y. Lee, Daniel R. Hines, Christopher Stafford, Christopher Soles, Eric K. Lin, Gottlieb Oehrlein
we performed a survey of the factors controlling the changes of the adhesion characteristics for PMMA and PET surfaces upon plasma activation of the respective interfaces for nanotransfer printing. Polar active functional groups introduced by plasma

Examination of thin film modulus for a series of poly(alkyl methacrylates)

March 22, 2009
Author(s)
Jessica M. Torres, Christopher Stafford, Bryan D. Vogt
In this work, the modulus of polymer thin films for a homologous series of poly(n-alkyl methacrylate)s will be discussed. In particular, the impact of the degree of undercooling from bulk Tg on the deviations will be explored as Tg is significantly

Quantifying Residual Stress in Nanoscale Thin Polymer Films via Surface Wrinkling

March 19, 2009
Author(s)
Jun Y. Chung, Thomas Q. Chastek, Michael J. Fasolka, Hyun W. Ro, Christopher Stafford
Residual stress, a pervasive consequence of solid materials processing, is stress that remains in a material after external forces have been removed. In polymeric materials, residual stress results from processes, such as film formation, that force and

Adhesion Research at the National Institute of Standard and Technology (NIST)

March 11, 2009
Author(s)
Donald L. Hunston, Christopher M. Stafford
Over the years, NIST has been very active in adhesion research. Although there has never been an organizational group or large-scale program that focused specifically on this topic, a wide variety of projects have had adhesion, or related properties, as a

Diffusion-controlled, self-organized growth of symmetric wrinkling patterns

March 1, 2009
Author(s)
Jun Y. Chung, Adam J. Nolte, Christopher Stafford
Nature is particularly adept at creating ordered patterns ranging from the wind-shaped ripples on a sand dune to spiral patterns found in sea shells or galaxies. Scientists have been striving to design systems with the same level of richness and complexity

Adhesion at layer-by-layer surfaces in aqueous environments

February 15, 2009
Author(s)
Adam J. Nolte, Jun Y. Chung, Marlon L. Walker, Christopher M. Stafford
Adhesion between materials is often governed by the ambient environment, which can mediate or change the types of molecular interactions present at an interface. Biological interactions, for example, can be mediated by factors such as temperature, ionic

Subsurface Patterning and its Effect on Interfacial Adhesion

February 15, 2009
Author(s)
Edwin P. Chan, Christopher M. Stafford
Nature (e.g. geckos and insects) has illustrated that a patterned surface can effectively tailor the adhesion of an interface. Inspired by the amazing attachment and detachment ability of these animals, significant efforts have been put forth to understand

Ultrathin Adhesives: Confinement Effect on Modulus

February 15, 2009
Author(s)
Jessica M. Torres, Christopher Stafford, Bryan D. Vogt
In this work, we will employ this wrinkling metrology to extract the modulus of polymer thin films for a homologous series of poly(n-alkyl methacrylate)s. In particular, we take advantage of the decrease in Tg as the alkyl chain length increases for these

In-situ Adhesion Measurements Utilizing Layer-by-layer Functionalized Surfaces

January 7, 2009
Author(s)
Adam J. Nolte, Jun Y. Chung, Marlon L. Walker, Christopher Stafford
The adhesion between poly(dimethylsiloxane) (PDMS) hemispheres coated with layer-by-layer (LbL) assemblies of polyelectrolytes was investigated using Johnson, Kendall, and Roberts (JKR) contact mechanics. Measurements were performed against amine

Complex micropatterning of periodic structures on elastomeric surfaces

July 10, 2008
Author(s)
Arnaud Chiche, Christopher Stafford, J Cabral
We report a simple methodology to fabricate complex sub-micron periodic structures in poly(dimethylsiloxane) over large surface areas (several cm2). Single-frequency, uni- and multi-axial sinusoidal surface modulations, with tunable amplitude and

Measuring the Modulus of Hydrated Contact Lenses via Surface Wrinkling

April 6, 2008
Author(s)
Jun Y. Chung, Young Jong Lee, Peyton Hopson, Michael J. Fasolka, Christopher Stafford
One of the most important considerations in the evaluation of hydrogels for biomedical and contact lens applications is the elastic modulus. The elastic modulus relates to several important factors including flexibility, comfort, adhesion, swelling

Quantifying Interfacial Adhesion in Transfer Printing via a Cantilever Peel Test

April 6, 2008
Author(s)
Jiong Liu, Jun Y. Chung, Christopher Stafford
Transfer printing has been demonstrated as a fabrication method for flexible organic electronics. The transfer printing process relies on the differential adhesion of a printable layer (PL) that is pressed between two substrates: transfer substrate (TS)

Synthesis and Characterization of Polymer Brushes from PDMS Surfaces

April 6, 2008
Author(s)
Heqing Huang, Adam J. Nolte, Jun Y. Chung, Christopher Stafford
In recent years, poly(dimethylsiloxane) (PDMS) has found increased application in the areas of microfluidic devices, chromatographic packing materials and membranes, as well as in medical and drug delivery devices. However, the hydrophobic surface of PDMS

High throughput adhesion testing using a modified edge lift-off test

February 17, 2008
Author(s)
Jiong Liu, Martin Chiang, Michael J. Fasolka, Christopher Stafford
The strength of an adhesively bonded joint depends on a host of factors such as surface treatment, roughness, materials properties, cure conditions and environmental variables. Therefore testing of adhesion within this large parameter space can be very