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Search Publications by

Christopher Stafford (Fed)

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Displaying 1 - 25 of 187

Specification for Interoperability Testing of Contactless Fingerprint Acquisition Devices

June 8, 2022
John M. Libert, Shahram Orandi, Bruce Bandini, Kenneth Ko, Craig I. Watson, Christopher Stafford, Matthew E. Staymates, John Grantham
This guidance specifies a protocol and associated metrics for the evaluation of contactless fingerprint acquisition device, and their interoperability with legacy devices. This protocol enables contactless fingerprint developers seeking certification of

Orientation of Thin Polyamide Layer-by-Layer Films on Non-Porous Substrates

December 16, 2021
Tawanda J. Zimudzi, Sarah E. Sheffield, Kathleen E. Feldman, Peter Beaucage, Dean DeLongchamp, Douglas I. Kushner, Christopher Stafford, Michael A. Hickner
The orientation of polyamide thin films on non-porous substrates was investigated using Fourier transform infrared (FTIR) spectroscopy and corroborated by near edge X-ray absorption fine structure (NEXAFS) measurements. Polyamide films comprised of m

Thickness-Dependent Permeability of Molecular Layer-By-Layer Polyamide Membranes

August 28, 2020
William D. Mulhearn, Vladimir Oleshko, Christopher Stafford
We present the thickness-dependent permeability of highly crosslinked polyamide (PA) membranes formed by a molecular layer-by-layer (mLbL) deposition process. The deposition allows for the synthesis of extremely smooth, uniform PA films of tunable

X-ray Scattering Studies of Reverse Osmosis Materials

August 25, 2020
Qinyi Fu, Nisha Verma, Benjamin S. Hsiao, Francisco J. Medellin-Rodriguez, Peter Beaucage, Christopher Stafford, Benjamin M. Ocko
Scarcity of freshwater is becoming a world crisis. In a recent annual risk report, the World Economic Forum lists it in their greatest global risk category. Currently, about four billion people live under conditions of severe water scarcity for at least

Water-Polyamide Chemical Interplay in Desalination Membranes explored by Ambient Pressure X-ray Photoelectron Spectroscopy

June 24, 2020
Sabrina Gericke, William D. Mulhearn, Dana E. Goodacre, Joseph Raso, Daniel J. Miller, Lauryn Carver, Slavomir Nemsak, Osman Karslioglu, Lena Trotochaud, Hendrik Bluhm, Christopher Stafford, Christin Buechner
Reverse osmosis using aromatic polyamide membranes is currently the most important technology for seawater desalination. The performance of reverse osmosis membranes is highly dependent on the interplay of their surface chemical groups with water and water

Quantifying Strain via Buckling Instabilities in Surface Modified Polymer Brushes

May 21, 2020
Cassandra M. Reese, Wei Guo, Brittany J. Thompson, Phillip K. Logan, Christopher Stafford, Derek L. Patton
We present a quantitative method of measuring the compressive strain of wrinkled polymer films and coatings with knowledge of the "skin" thickness, wrinkle wavelength, and wrinkle amplitude. The derived analytical expression is validated with a well

Nanoscale Pattern Decay Monitored via in-situ Heated Atomic Force Microscopy

March 12, 2020
Sonal Bhadauriya, Jianan Zhang, Jaejun Lee, Michael R. Bockstaller, Alamgir Karim, Richard J. Sheridan, Christopher Stafford
We combine in-situ heated atomic force microscopy (AFM) with automated line-by-line spectral analysis to quantify the relaxation or decay of nanopatterned polymer films at temperatures above the glass transition. This approach enables assessment of pattern

Insights into the Water Transport Mechanism in Polymeric Membranes from Neutron Scattering

February 5, 2020
Edwin P. Chan, Bradley R. Frieberg, Jacob Daniel Tarver, Madhusudan Tyagi, WenXu Zhnag, Bryan Coughlin, Christopher M. Stafford, Abhishek Roy, Steve Rosenberg, Christopher L. Soles
Polymeric membranes are ubiquitous in a number of transport ap- plications including gas separation, water desalination, solid state batteries and fuel cells. The permeability and selectivity of these membranes are intimately linked to the structure and

Reduced Holey Graphene Oxide Membranes for Desalination with Improved Water Permeance

December 13, 2019
Xiaoyi Chen, Zhihao Feng, Janavi Gohil, Christopher Stafford, Ning Dai, Liang Huang, Haiqing Lin
Reduced-graphene oxide (r-GO) membranes with narrow channels exhibit salt rejections comparable to conventional nanofiltration (NF) membranes. However, their water permeances are much lower because of the high tortuosity for water permeation. Herein we

Unexpectedly Strong Size-Sieving Ability in Carbonized Polybenzimidazole for Membrane H2/CO2 Separation

November 21, 2019
Maryam Omidvar, Hien Nguyen, Liang Huang, Cara Doherty, Anita Hill, Christopher Stafford, Xianshe Feng, Mark Swihart, Haiqing Lin
Polymers with high permeability and strong size-sieving ability are needed for H2/CO2 separation at temperatures ranging from 100 °C to 300 °C to enable an energy-efficient pre- combustion CO2 capture process. However, such polymers usually suffer from a

A general approach to multicomponent metal-decorated crumpled reduced graphene oxide nanocomposites using a flame-based process

September 25, 2019
Mohammad M. Mohammadi, Shikuan Shao, Santosh S. Gunturi, Anirudh R. Raghavan, Naveshkaanth Alexander, Christopher Stafford, Raymond D. Buchner, Mark Swihart
A general approach to multicomponent metal-decorated crumpled reduced graphene oxide nanocomposites using a flame-based process Mohammad Moein Mohammadi1, Shikuan Shao1, Santosh Srivatsa Gunturi1, Anirudh Ravi Raghavan1, Naveshkaanth Alexander1

Sequential and one-pot post-polymerization modification reactions of thiolactone-containing polymer brushes

August 19, 2019
Cassandra M. Reese, Brittany J. Thompson, Phillip K. Logan, Christopher Stafford, Derek L. Patton, Michael Blanton
Thiolactone chemistry has garnered significant attention as a powerful post-polymerization modification (PPM) route to mutlifunctional polymeric materials. Here, we apply this versatile chemistry to the fabrication of ultrathin, multifunctional polymer

Effect of Adjacent Hydrophilic Polymer Thin Films on Physical Aging and Residual Stress in Thin Films of Poly(butylnorbornene-ran-hydroxyhexafluoroisopropyl norbornene)

June 22, 2019
Elizabeth A. Lewis, Christopher Stafford, Bryan D. Vogt
The properties of thin supported polymer films can be dramatically impacted by the substrate upon which it resides. A simple way to alter the properties of the substrate (chemistry, rigidity, dynamics) is by coating it with an immiscible polymer. Here we

Controlled Growth of Polyamide Films atop Homogeneous and Heterogeneous Hydrogels using Gel- Liquid Interfacial Polymerization

May 22, 2019
Mengyuan Wang, Christopher Stafford, Lewis M. Cox, Adrienne K. Blevins, Masoud Aghajani, Jason Killgore, Yifu Ding
Interfacially polymerized polyamide (PA) layers dictate the permselective performance of thin film composite (TFC) membranes. Extensive effort has been focused on understanding and ultimately controlling the structure and morphology of the PA layers on

Tuning the Relaxation of Nano-Patterned Polymer Films with Polymer-Grafted Nanoparticles: Observation of Entropy-Enthalpy Compensation

November 6, 2018
Sonal Bhadauriya, Xiaoteng Wang, Jack F. Douglas, Praveen Pitliya, Jianan Zhang, Dharmaraj Raghavan, Michael R. Bockstaller, Christopher Stafford, Alamgir Karim
Polymer films provide a versatile "plastic" material in which complex functional relief patterns can be imprinted with a resolution down to tens of nanometers. However, the utility of such patterned materials is limited by the tendency of imprinted

Short-time dental resin biostability and kinetics of enzymatic degradation

May 9, 2018
Xiaohong Wang, Sheng Song, Lei Chen, Christopher M. Stafford, Jirun Sun
Resin biostability is an important concern regarding the durability of methacrylate-based dental resin restorations. Current resin biostability evaluation methods take considerable time, from weeks to months, and provide no short-time kinetics of resin