Microsculptures made easy

Minerals assemble on demand into tiny, complex shapes like flowers

FLORAL DISPLAY Red flowerlike structures grew on green spiral stems. Scientists can grow such structures from minerals by carefully manipulating pH, temperature and carbon dioxide concentration. This micrograph is false colored but reflects the structure's actual colors.

Courtesy of Wim Noorduin

The art of growing tiny, intricate floral structures has become a science. Researchers can now grow fields of complex little mineral structures on demand. The process could lead to chemical tricks that halt the growth and movement of bacteria.

When minerals emerge from solution as dazzling crystals, their shapes are often as much about luck as planning. Another way to make small structures is to etch them from large pieces of material, a process that’s laborious and expensive. Now a team from Harvard University has shown how to easily orchestrate the growth of specific structures just by changing the local environment of minerals in solution.

“You tell me what you want and I will dial in your structure,” says materials scientist Joanna Aizenberg. 

The researchers start by putting a glass plate in a beaker containing water, a salt (barium chloride) and liquid glass (sodium metasilicate). These minerals precipitate onto the plate in shapes dictated by variables such as temperature and carbon dioxide concentration. To build a miniature tulip, for example, the researchers add some table salt to the solution, and the minerals precipitate as a dome shape, about 25 micrometers across at the base. This spurs new chemistry that prompts slender stems to emerge. When Aizenberg’s team lets a little carbon dioxide diffuse into the solution, the stems bloom into dainty cups, the team reports in the May 17 Science.

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