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Search Publications by: Christopher Stafford (Fed)

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Displaying 101 - 125 of 203

Manipulation of adhesion via sub-surface patterning

February 13, 2011
Author(s)
John A. Howarter, Peter M. Johnson, Jun Y. Chung, Christopher Stafford
The delamination characteristics of patterned and hierarchical interfaces are of great interest due to the advanced adhesion capabilities found with many biological surfaces. Using nature-inspired design principles, micro- and nanostrucutred surfaces have

OCT For Depth Detection of Buried Particles in Polymeric Materials

February 13, 2011
Author(s)
Robert C. Chang, Anant Agrawal, Peter M. Johnson, Christopher Stafford
In this work, we demonstrate a method to produce novel optical phantoms usable for the characterization of OCT axial resolution and contrast. By varying the diameter of the microspheres and the thickness of the polymer layers, different spatial frequencies

System-independent assessment of OCT axial resolution with a bar chart phantom

February 10, 2011
Author(s)
Robert C. Chang, Jeeseong Hwang, Christopher M. Stafford, Anant Agrawal, T. Joshua Pfefer, Megan Connors
We present a novel optical phantom approach for the characterization of OCT axial resolution and contrast via multilayered “bar charts.” We explored two methods to fabricate these phantoms: the first is based on a combinatorial methods approach from

Comment on Viscoelastic properties of con ned polymer lms measured via thermal wrinkling by Edwin P. Chan, Kirt A. Page, Se Hyuk Im, Derek L. Patton, Rui Huang and Christopher M. Stafford, Soft Matter (Communications), 5, 4638 4641 (2009).

January 11, 2011
Author(s)
Paul A. O'Connell, Greg B. McKenna, Edwin Chan, Christopher Stafford
Recently Chan et al. published a paper describing a method to use the wrinkling of a thin elastic film on which is adhered a thin polymer film to extract the viscoelastic properties of the polymer. Results were presented for the rubbery plateau modulus and

Instabilities as a Measurement Tool for Soft Materials

November 2, 2010
Author(s)
John A. Howarter, Christopher Stafford
Mechanical instabilities such as wrinkles, creases, and folds have long been viewed as a source of frustration for engineers and often a point of curiosity among scientists. Scientists aspire to understand the underlying physics behind the formation of

Thickness dependence of the elastic modulus of tri (8-hydroxyquinolinato) aluminum (III)

November 2, 2010
Author(s)
Jessica M. Torres, Nathan Bakken, Christopher Stafford, Jian Li, Bryan D. Vogt
The intrinsic flexibility of organic molecules has been suggested to enable bendable electronics in comparison to their stiffer, inorganic counterparts. However, very little is known regarding the mechanical properties of these conjugated molecular glasses

Investigation of Thermally Responsive Block Copolymer Thin Film Morphologies Using Surface Gradients

October 20, 2010
Author(s)
Jennifer Y. Kelly, Julie N. Albert, John A. Howarter, Shuhui Kang, Christopher Stafford, Thomas H. Epps, Michael J. Fasolka
We report the use of a gradient library approach to characterize the structure and behavior of thin films of a thermally-responsive block copolymer (BCP), poly(styrene-b-tert-butyl acrylate), that exhibits chemical deprotection and morphological changes

Surface Wrinkling: a Versatile Platform for Measuring Thin Film Properties

September 2, 2010
Author(s)
Jun Y. Chung, Adam J. Nolte, Christopher M. Stafford
Surface instabilities in soft matter have captivated the scientific community for decades. Recently, surface wrinkling has received a great deal of attention due to its simplicity and well-established mechanics of formation. Particularly, the use of

Surface Energy/Chemistry Gradients for Block Copolymer Thin Film Studies

August 2, 2010
Author(s)
Julie N. Albert, Michael J. Baney, Christopher Stafford, Jennifer Y. Kelly, Thomas H. Epps
Development of self-assembling block copolymer materials for emerging nanotechnologies requires an understanding of how surface energy and chemistry affect thin film phase behavior. Gradient methods provide an effective route to explore the role of surface

Impact of molecular mass on the elastic modulus of polystyrene thin films

July 31, 2010
Author(s)
Jessica M. Torres, Christopher Stafford, Bryan D. Vogt
Euler wrinkling was used to determine the elastic modulus at ambient temperature of polystyrene (PS) films of varying thickness and relative molecular mass (Mn). A range of Mn from 1.2 kg/mol to 990 kg/mol was examined to determine if the molecular size

Challenges in Sustainable Polymeric Materials

May 19, 2010
Author(s)
Kathryn L. Beers, Christopher M. Stafford
While there are many societal and economic factors that contribute to a sustainable civilization, there are also real technical and scientific problems that must be solved to provide the materials necessary to make progress towards the goal of

Adhesion research at the National Institute of Standards and Technology (NIST)

April 1, 2010
Author(s)
Christopher M. Stafford, Adam J. Nolte, Gale A. Holmes, Sheng Lin-Gibson, John A. Howarter
NIST s involvement in adhesion research has been wide ranging and is ultimately in response to interactions between individual project leaders and our industrial partners. In this way, NIST s participation in the Adhesion Society has been instrumental in

Wrinkling and Strain Softening in Single-Wall Carbon Nanotube Membranes

March 26, 2010
Author(s)
Erik K. Hobbie, Daneesh O. Simien, Jeffrey A. Fagan, JiYeon Huh, Jun Y. Chung, Steven D. Hudson, Jan Obrzut, Jack F. Douglas, Christopher M. Stafford
Ultrathin layers of single-wall carbon nanotubes (SWCNTs) show considerable promise for applications ranging from fuel-cell membranes and biochemical sensors to bioactive films and transparent electrodes. The high conductivity and extreme anisotropy of

Harnessing Wrinkle Delamination Mechanics to Measure and Pattern Polymer Coatings

March 21, 2010
Author(s)
Adam J. Nolte, Jun Y. Chung, Christopher Stafford
Compressive stresses in stiff polymer coatings can give rise to surface instabilities in which the coating adopts a sinusoidally wrinkled morphology with a dominant wavelength, d, as displayed in Figure 1a. Such instabilities are generally observed for

Influence of molecular mass on the modulus of thin polystyrene films

March 21, 2010
Author(s)
Jessica M. Torres, Christopher Stafford, Bryan D. Vogt
In this work, we examine the influence of relative molecular mass (Mn, or the number average molecular mass) of PS on the thickness-dependent moduli using a wrinkling based instability of a stiff film on an elastic substrate. This wrinkling based metrology
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