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Calling on pappi to pipette and celebrating the Fourth of July with chemistry

by Stephen K. Ritter
July 3, 2017 | A version of this story appeared in Volume 95, Issue 27


Please pass the pappi

A dandelion pappus picks up a tiny droplet of water.
Credit: Adv. Funct. Mater.
Pipettin’ pappus: Omniphilic weed seed carrier draws a droplet.

The dandelion, Taraxacum officinale, is a maligned weed, cursed by many a curmudgeon gardener the world over for infesting lawns and crops. The curse isn’t universal, mind you, as some health food aficionados eat the greens, and fans of author Ray Bradbury are known to turn the flowers into wine. But generally the dandelion is unwanted.

Researchers including Feng Xu and Tian Jian Lu at Xi’an Jiaotong University and Guy M. Genin at Washington University in St. Louis have now found an application for the lab: using the pappus of a dandelion seed—the familiar white fluffy “parachute” that enables the seed to be carried by the wind—as a micropipette (Adv. Funct. Mater. 2017, DOI: 10.1002/adfm.201606607).

“We found you can actually use dandelion seeds to perform precise droplet handling,” says Genin, a mechanical engineer. “There aren’t many tools that exist for this.”

Although most materials can be wetted only by water (hydrophilic) or oil (oleophilic), the researchers found the dandelion pappus is omniphilic, meaning the fibrous structure can be saturated by both types of liquids. The pappus collapses if you dip it in either water or oil, Xu explains. That allows someone with a deft hand to lift up a nanoliter-sized drop of water and deposit it into a pool of oil. The same lab hand can go back into the oil and use the pappus to retrieve the drop of water.

“The dandelion comes self-assembled and naturally grown, and its seeds are able to reliably and repeatedly pick up these tiny volumes of fluid,” Genin says. The seeds can be used individually or in arrays to collect greater amounts of liquid. The next step is to replicate the dandelion’s omniphilic properties in synthetic materials, he adds. “We hope to be able to develop bioinspired omniphilic surfaces to create additional options for handling liquids.”

The bible of bang and boom

Credit: Chicago Review Press
Boom goes the dynamite: Explosives galore in new tome.
The cover for the new book “Boom!” showing a firecracker exploding.
Credit: Chicago Review Press
Boom goes the dynamite: Explosives galore in new tome.

If you’re hankering for something chemically different on U.S. Independence Day, there’s a new book out: “Boom! The Chemistry and History of Explosives.” This volume, by Simon Quellen Field, is advertised as “the go-to handbook for the armchair science buff looking past the oh and the ah of fireworks for a basic understanding of the chemistry that makes them possible.”

If Field sounds familiar, it’s because he is author of “Why There’s Antifreeze in Your Toothpaste” and creator of the Science Toys website, “Boom!” provides details about the scientists “who burst chemistry wide open,” getting into how energetic materials such as black powder, TNT, and rocket fuels work on a molecular level and touching on the history behind “blowout discoveries.” Okay, the superlative verbiage is from the new book’s promotional material, but it looks like a promising read this Fourth of July with a slice of cold watermelon.

Steve Ritter wrote this week’s column. Please send comments and suggestions to



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