Advertisement

If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.

ENJOY UNLIMITED ACCES TO C&EN

Materials

Coffee stains point way to making tiny lines

January 16, 2006 | A version of this story appeared in Volume 84, Issue 3

As a drop of coffee evaporates, capillary flows shuttle residue to the diminishing drop's edges, leaving behind dark rings. Saurabh Vyawahare, Kate M. Craig, and Axel Scherer of California Institute of Technology have found that this phenomenon can be exploited to make extremely fine lines by using surfactant-containing liquids (Nano Lett., published online Jan. 5, dx.doi.org/10.1021/nl0522678). Potential applications include making nanowires and light-manipulating photonic crystals constructed from arrays of tiny ceramic or polymeric spheres that can be carried along and organized by the capillary flows, Vyawahare says. Instead of letting the line-forming solutions evaporate in the open the way a coffee drop does, the researchers sandwich the liquids between wettable surfaces. When they use photolithography or other means to create "pinning points" on the surfaces, the evaporating liquid recedes from the points, reeling out a filament of liquid. By including fluorescent quantum dots in the solution, the researchers can visualize the process and the result, such as the line formed between two pinning points shown above.

Article:

This article has been sent to the following recipient:

0 /1 FREE ARTICLES LEFT THIS MONTH Remaining
Chemistry matters. Join us to get the news you need.