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: Visualizing anisotropic carrier transport in organic semiconductor materials

Related Stories

Research could lead to biodegradable computer chips

7 hours ago

Portable electronics - typically made of non-renewable, non-biodegradable and potentially toxic materials - are discarded at an alarming rate in consumers' pursuit of the next best electronic gadget.

Driest place on Earth hosts life

May 19, 2015

Researchers have pinpointed the driest location on Earth in the Atacama Desert, a region in Chile already recognised as the most arid in the world. They have also found evidence of life at the site, a discovery ...

CLAIRE brings electron microscopy to soft materials

May 14, 2015

Soft matter encompasses a broad swath of materials, including liquids, polymers, gels, foam and - most importantly - biomolecules. At the heart of soft materials, governing their overall properties and capabilities, ...

Recommended for you

Researchers prove magnetism can control heat, sound

5 hours ago

Phonons—the elemental particles that transmit both heat and sound—have magnetic properties, according to a landmark study supported by Ohio Supercomputer Center (OSC) services and recently published by ...

How researchers listen for gravitational waves

14 hours ago

A century ago, Albert Einstein postulated the existence of gravitational waves in his General Theory of Relativity. But until now, these distortions of space-time have remained stubbornly hidden from direct ...

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.