U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Search Publications

NIST Authors in Bold

Displaying 451 - 475 of 1719

Dielectrophoretic Cell Capture on Polyester Membranes

April 2, 2012
Author(s)
Conni Hanke, Petra S. Dittrich, Darwin Reyes-Hernandez
A new system for dielectrophoretic cell capture on porous polyester (PET) membranes is presented. Conventional photolithographic techniques were used to fabricate gold microelectrodes on a PET membrane. We characterized these electrodes to proof that there

In Situ Raman Monitoring of Ring-Opening Copolymerizations

March 25, 2012
Author(s)
Matthew T. Hunley, Santanu S. Kundu, Peter M. Johnson, Kathryn Beers
Recent advances in enzyme, metal, and organic catalysts have enabled the development of advanced functional polymers from cyclic ester and cyclic carbonate monomers. In this work, we present an in situ technique to monitor ring-opening polymerization using

Freeform Fabricated Scaffolds with Roughened Struts that Enhance both Stem Cell Proliferation and Differentiation by Controlling Cell Shape

March 1, 2012
Author(s)
Girish Kumar, Carl G. Simon Jr., Michael S. Waters, Tanya M. Farooque, Marian F. Young
We demonstrate that imparting freeform fabricated (FFF) scaffolds with surface roughness on their struts enhances osteogenic differentiation of primary human bone marrow stromal cells (hBMSCs) by controlling cell shape. Previous work showed that hBMSCs

Ultra-small-Angle X-ray Scattering - X-ray Photon-Correlation Spectroscopy Studies of Incipient Structural Changes in Amorphous Calcium Phosphate Based Dental Composites

February 28, 2012
Author(s)
Fan Zhang, Andrew J. Allen, Lyle E. Levine, Laura Espinal, Joseph M. Antonucci, Drago Skrtic, Justin N. O'Donnell, Jan Ilavsky
The local structural changes in amorphous calcium phosphate (ACP) based dental composites were studied upon heating using both static, bulk measurement techniques and recently developed ultra-small angle X-ray scattering - X-ray photon correlation

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

In situ monitoring of enzyme-catalyzed (co)polymerizations by Raman spectroscopy

November 10, 2011
Author(s)
Matthew T. Hunley, Atul Bhangale, Santanu S. Kundu, Peter M. Johnson, Michael S. Waters, Richard Gross, Kathryn Beers
In situ, fiber optic-based Raman spectroscopy provided real time monitoring of enzyme-catalyzed ring-opening homo- and copolymerizations of ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL). A custom designed reactor equipped with in situ fiber optic probe

Synthesis and characterization of antimicrobial dimethacrylates containing quaternary ammonium functionalities for dental and biomedical applications

October 27, 2011
Author(s)
Joseph M. Antonucci, Diana N. Zeiger, Sheng Lin-Gibson, Bruce O. Fowler, Nancy J. Lin
The widespread incidence of recurrent caries has resulted in the need for improved dental restorative materials, including effective antibacterial, polymeric dental materials. Compounds with quaternary ammonium groups are known to reduce bacterial growth

Influence of chain stiffness on thermal and mechanical properties of polymer thin films

October 25, 2011
Author(s)
Jessica M. Torres, Chengqing C. Wang, E. B. Coughlin, John P. Bishop, Richard A. Register, Robert A. Riggleman, Christopher Stafford, Bryan D. Vogt
The effect of main chain stiffness and side chain flexibility on the elastic modulus and glass transition temperature (Tg) of thin polymer films is investigated using non-traditional polymers formed from 5-(2-phenylethylnorbornene). Depending on the

Morphological Changes Driven by Nanofibrous Scaffolds Induce Marrow Stromal Cell Osteogenesis

October 11, 2011
Author(s)
Carl G. Simon Jr., Kaushik Chatterjee, Christopher K. Tison, Girish Kumar, Patrick S. Pine, Marc L. Salit, Jennifer H. McDaniel, Marian F. Young
Cells are sensitive to tissue scaffold architecture and these cell-material interactions drive cell functions critical in tissue regeneration. Results presented here demonstrate that nanofiber scaffolds force primary human bone marrow stromal cells (hBMSCs

Block copolymer photonic gel for mechanochromic sensing

September 19, 2011
Author(s)
Edwin Chan, Joseph J. Walish, Edwin L. Thomas, Christopher Stafford
In this work, we describe a strategy based on mechanochromic sensing, the coupling between mechanical and optical properties, of a block copolymer photonic gel. Although this phenomena has been observed in many materials, we demonstrate this concept for

Characterizing the Mechanical Properties and Degradation of Thin Polymer Membranes

August 28, 2011
Author(s)
Christopher M. Stafford, Jun Y. Chung, Junghyun Lee
The elasticity, strength, and toughness of thin polymer membranes are of considerable interest since direct knowledge of these key mechanical properties can provide insight into performance, durability, and underlying degradation mechanisms that occur over

Modeling Enzymatic Kinetic Pathways for Ring-Opening Lactone Polymerization

August 11, 2011
Author(s)
Peter M. Johnson, Santanu S. Kundu, Kathryn Beers
A unified kinetic pathway for the enzyme catalyzed polymerization and degradation of poly(ε-caprolactone) was developed. This model tracks the complete distribution of individual chain lengths, both enzyme-bound and in solution, and successfully predicts

Using Block Copolymer Self-Assembly to Imprint the Crystallization of Polymer Dendrites

August 10, 2011
Author(s)
Sangcheol Kim, Alamgir Karim, Jack F. Douglas, Christopher L. Soles, R M. Briber
We utilize the self-assembly of cylinder-forming block copolymer (BCP) films to create templates for dendritic polymer crystallization patterns. This templating was achieved by simply spin-casting thin films from a solution containing both the BCP

Analyses of a Cantilever-Beam Based Instrument for Evaluating the Development of Polymerization Stresses

August 9, 2011
Author(s)
Martin Y. Chiang, Anthony A. Giuseppetti, Joy P. Dunkers, Jing Qian, Sheng Lin-Gibson, Gary E. Schumacher, Joseph M. Antonucci
Analytical and finite element analyses have been performed on a cantilever-beam based methodology (tensometer) for evaluating the development of stresses as the concomitant of constrained polymerization shrinkage. A guideline for designing a tensometer

Design and Optimization of a Permeation Testing System for Polymer Coatings

August 8, 2011
Author(s)
Adrian E. Verwolf
Measurements of liquid permeation through freestanding Parylene C membranes were made using a high- performance testing system, which demonstrated fast response (≤ 30 seconds) to changing concentrations in the sweep gas stream and detectability of less
Displaying 451 - 475 of 1719