Designer Gradients Speed Surface Science Experiments

Jun 08, 2006
Designer Gradients Speed Surface Science Experiments

Researchers from the National Institute of Standards and Technology have demonstrated an elegantly simple technique for synthesizing a wide variety of complex surfaces that vary in a controlled fashion across a test strip. The new technique is so flexible that it can be applied to surface science experiments ranging from developing better paints to exploring the bonding of proteins to cell membranes.

So-called “gradient composition surfaces”—their chemical composition changes gradually across the surface—have been shown to be powerful research tools for rapid, high-throughput testing of complicated surface properties, but they can be tricky to build. The new NIST technique described in a recent paper in Advanced Materials coats a silicon wafer with a brush-like copolymer surface, varying the relative concentration of two components, or monomers, of the polymer along the length of the substrate. The dense polymer brush provides a controlled interaction surface at the top while effectively masking the underlying substrate.

The heart of the NIST technique is a combined microfluidic mixer and reaction chamber. The two components are injected into the mixer with gradually changing flow rates and mix thoroughly before filling a thin reaction chamber holding the silicon wafer substrate. Once the solution leaves the mixing region, the narrow dimensions of the reaction chamber inhibit further mixing, so the varying composition ratios through the chamber remain stable while the solution polymerizes on the substrate.

Because it keeps the fluid mixture concentrations stable for long periods, the new technique is unique in its ability to accommodate a wide variety of materials, potentially producing test surfaces for studying surface phenomena ranging from nanoscale interactions of biomolecules—critical for improving the performance of tissue-engineered medical products or for identifying the fundamental mechanisms key to cell/surface adhesion—to the performance of new products like paints or adhesives. The specific polymer used in these proof-of-concept experiments, for example, is typical of a temperature- or acidity-sensitive polymer that might be used in a drug delivery system.

Citation: C. Xu, S.E. Barnes, T. Wu, D.A. Fischer, D.M. DeLongchamp, J.D. Batteas, and K.L. Beers. Solution and surface composition gradients via microfluidics confinement: fabrication of a statistical-copolymer-brush composition gradient. Adv. Mater. 2006, 18, 1427-1430.

Source: NIST

Explore further: Improving insulation materials, down to wetting crossed fibers

Related Stories

Chemists characterize 3-D macroporous hydrogels

Jun 30, 2015

Carnegie Mellon University chemists have developed two novel methods to characterize 3-dimensional macroporous hydrogels—materials that hold great promise for developing "smart" responsive materials that ...

Sweeping lasers snap together nanoscale geometric grids

Jun 23, 2015

Down at the nanoscale, where objects span just billionths of a meter, the size and shape of a material can often have surprising and powerful electronic and optical effects. Building larger materials that ...

NASA studies Louisiana's changing wetlands

Jun 17, 2015

NASA recently completed an intensive study of Louisiana Gulf Coast levees and wetlands, making measurements with three advanced imaging instruments on two research aircraft.

Recommended for you

How oversized atoms could help shrink

20 hours ago

"Lab-on-a-chip" devices – which can carry out several laboratory functions on a single, micro-sized chip – are the result of a quiet scientific revolution over the past few years. For example, they enable ...

Physicists shatter stubborn mystery of how glass forms

Jun 29, 2015

A physicist at the University of Waterloo is among a team of scientists who have described how glasses form at the molecular level and provided a possible solution to a problem that has stumped scientists ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.