Frozen oil droplets morph and shine

Hydrocarbon crystals could eventually serve as drug delivery vessels

oil droplet shapes

COLORFUL CREATIONS  When frozen, these hydrogen-carbon droplets form crystals with a variety of customizable shapes.

N. Denkov et al/nature 2015

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In carefully chilled conditions, microscopic beads of oil freeze to form a panoply of shapes. 

The triangles, hexagons and other structures above are oil droplets tens of micrometers across that are mixed with water and a detergent-like substance, and then slowly frozen to form hydrogen-carbon crystals. Polarized light passing through the crystals disperses to create the kaleidoscopic color displays. University of Cambridge materials scientist Stoyan Smoukov and colleagues described the assorted shapes and the recipes for crafting them in the Dec. 17 Nature.

Scientists have observed similar transformations in other hydrocarbons, but this is the first time researchers have managed to manipulate the droplets’ shape-shifting, Smoukov says. His team varied detergent types and cooling speeds to control the geometries of the droplets. All four droplets in the top row are made of the same substance, a chemical chain of 16 carbon and 34 hydrogen atoms. The other crystals contain from 14 to 20 carbons.

The new technique may allow scientists to efficiently produce an assortment of custom-shaped miniature bricks. Those bricks, Smoukov says, could serve as building blocks for larger, more complex structures, or as vessels for delivering drugs inside the body.

COOL CHOREOGRAPHY  Oil droplets shape-shift as they are gradually cooled in a mix of water and a detergent-like compound. In the video above, the droplets are hexadecane, a chain of 16 carbon and 34 hydrogen atoms. At the moment that the droplets fully freeze, newly formed plastic crystals flash colorfully under polarized light.

N. Denkov et al/Cambridge University

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