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Search Publications by: Christopher Stafford (Fed)

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Displaying 51 - 75 of 197

Spray-deposition and photopolymerization of organic-inorganic thiol-ene resins for fabrication of superamphiphobic surfaces

June 9, 2014
Author(s)
Li Xiong, Laken Kendrick, Hannele Heusser, Bradley J. Sparks, Christopher Stafford, James T. Goetz, Sergei Nazarenko, Derek L. Patton
Superamphiphobic surfaces, exhibiting high contact angles and low contact angle hysteresis to both water and low surface tension liquids, have attracted a great deal of attention in recent years due to the importance in many practical applications. In this

Confinement-Driven Increase in Ionomer Thin-Film Modulus

April 28, 2014
Author(s)
Kirt A. Page, Ahmet Kusoglu, Christopher M. Stafford, Sangcheol Kim, Regis J. Kline, Adam Weber
Ion-conductive polymers, or ionomers, are critical materials for a wide range of electrochemical technologies. For optimizing the complex, heterogeneous structures in which they occur, there is a need to elucidate the governing structure/function

Tailoring the Permselectivity of Water Desalination Membranes via Nanoparticle Assembly

January 6, 2014
Author(s)
Edwin Chan, William Mulhearn, Jung-Hyun Lee, Daeyeon Lee, Christopher Stafford
: Thin film composite membranes can selectively separate mono- and di-valent ions from water via solution-diffusion of each species through a dense but ultrathin, highly crosslinked polymer ‘skin' layer - water is transported across the membrane faster

Elasticity and rigidity percolation in networks of type-purified single-wall carbon nanotubes on flexible substrates

October 29, 2013
Author(s)
John M. Harris, JiYeon Huh, Matthew R. Semler, Christopher Stafford, Steven Hudson, Jeffrey Fagan, Erik K. Hobbie
Wrinkles and folds in compressed thin films of type-purified single-wall carbon nanotubes (SWCNTs) on polydimethylsiloxane (PDMS) substrates are used to study the mechanical response of pristine nanotube networks. While the low-strain plateau moduli are

Swelling of Ultrathin Molecular Layer-by-Layer Polyamide Water Desalination Membranes

September 30, 2013
Author(s)
Edwin P. Chan, Allison P. Young, Jung-Hyun Lee, Christopher M. Stafford
The water vapor swelling behavior of ultrathin crosslinked aromatic polyamide films, synthesized via molecular layer-by-layer deposition, is characterized via specular X-ray reflectivity. The results show that these films expand only along the thickness

Feeling Small: Exploring the tactile perception limits

September 12, 2013
Author(s)
Lisa Skedung, Martin Arvidsson, Jun Y. Chung, Christopher Stafford, Birgitta Berglund, Mark W. Rutland
The human finger is exquisitely sensitive in distinguishing different materials, but the question remains as to what length scales are capable of being discriminated in active touch? We combine psychophysical approaches with materials science to

Molecular Layer-by-Layer Assembled Reverse Osmosis Membranes for Water Desalination

July 12, 2013
Author(s)
Joung-Eun Gu, Seunghye Lee, Wansuk Choi, Jong Suk Lee, Bo-Young Kim, Edwin Chan, Christopher Stafford, Jun-Young Chung, Joona Bang, Jung-Hyun Lee
Here, we report on the successful design, construction, and performance of membranes constructed using the mLbL process and show that these membranes exceed the performance of membranes synthesized through conventional interfacial polymerization. In our

Spontaneous wrinkling in azlactone-based functional polymer thin films in 2d and 3d geometries for guided nanopatterning

February 4, 2013
Author(s)
Muruganathan Ramanathan, Bradley S. Lokitz, Jamie M. Messman, Christopher Stafford, S. M. Kilbey
We report a simple, one step process for developing wrinkling patterns in azlactone-based polymer thin films and brushes in 2D and 3D surfaces. The polymer used in this work wrinkles spontaneously upon deposition and solidification on a substrate without

Swelling of ultrathin crosslinked polyamide water desalination membranes

December 27, 2012
Author(s)
Edwin P. Chan, Allison P. Young, Jung-Hyun Lee, Jun-Young Chung, Christopher M. Stafford
We study the water swelling behavior of semi-aromatic crosslinked polyamide ultrathin films in order to characterize the materials properties of the polymer network. Specifically, we utilize X-ray reflectivity and quartz crystal microbalance to measure

Anisotropic, Hierarchical Surface Patterns via Surface Wrinkling of Nanoimprinted Polymer Films

October 22, 2012
Author(s)
Junghyun Lee, Hyun W. Ro, Rui Huang, Thomas Germer, Paul Lemaillet, Christopher Soles, Christopher Stafford
we demonstrated the wrinkling behavior of nanopatterned PS films, whose wrinkle wavelength and resultant morphology depend strongly on geometric parameters of surface patterns as well as the direction of the applied strain relative to the nanopattern

Viscoelastic and poroelastic relaxations of polymer-loaded hydrogels

July 5, 2012
Author(s)
Blessing Deeyaa, Christopher Stafford, Edwin Chan, Peter M. Johnson
In this work, we study the viscoelastic and poroelastic contributions on the relaxation behavior of a polymer-loaded hydrogel using a recently develop Poroelastic Relaxation Indentation (PRI) measurement technique. By applying a generalized relaxation

Synthesis and characterization of model crosslinked polyamide films for water purification

June 24, 2012
Author(s)
Peter M. Johnson, Edwin Chan, Jun Y. Chung, Junghyun Lee, Christopher Stafford
Reverse osmosis (RO) and nanofiltration (NF) membranes are comprised of a dense active layer supported by a porous support. Commercial active layer are highly crosslinked polyamides that are formed through interfacial polymerization directly on the support

Rippling Instability of Supported Polymer Nanolines

February 21, 2012
Author(s)
Vijaya R. Tirumala, Christopher M. Stafford, Leonidas E. Ocola, Jack F. Douglas, L. Mahadevan
The swelling response of polymer line gratings supported on a rigid substrate has direct implications on their mechanical stability during pattern transfer in nanofabrication. The polymer lines, when swollen in a good solvent, undergo a rippling

Spherical indentation testing of poroelastic relaxations in thin hydrogel layers

December 16, 2011
Author(s)
Edwin Chan, Yuhang Hu, Peter M. Johnson, Zhigang Suo, Christopher Stafford
In this work, we present the Poroelastic Relaxation Indentation (PRI) testing approach for quantifying the mechanical and transport properties of thin layers of poly(ethylene glycol) hydrogel materials with thicknesses on the order of 200 m. Specifically

Mechanical Properties of Polymer Nano-Films

November 28, 2011
Author(s)
Junghyun Lee, Jun Y. Chung, Christopher Stafford
Three fundamental mechanical properties of supported glassy polystyrene films with thickness ranging from 250 nm to 9 nm were quantitatively determined by a recently developed wrinkling-cracking method. Films below about 40 nm showed a decrease in both