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Breakthroughs, Briefly

No-Frills Device Tracks Pollutants

Standard sensors that are used to detect water contamination require electronics, which constrains where and how they can operate. But assistant professor of mechanical engineering Sindy K.Y. Tang and her team have invented a “time capsule” that indicates when chemicals appear in water and in what concentration without using electronics, mechanical parts or batteries. When placed in a moving stream, their simple, pinky-sized and inexpensive sensor records information about the time and the path of the sensor’s flow, thereby enabling a researcher to backtrack to the location of the contaminants. Tang says she was partly inspired by the way tree rings record environmental history.

The device contains two tiny tubes, each filled with a gel. One end of each tube connects to a common reservoir of a chemical that diffuses through the gel at a predictable rate, serving as the timer for the device. The other end of each tube is open to capture water. An ensuing reaction between a contaminant and the timer chemical leaves a permanent mark on the gel, which can be interpreted to reveal where along the streambed the capsule first encountered the contaminant.

While this breakthrough is already helping identify pollution sources in streams, the team’s longer-term aspirations include mapping deep underground environments. To do so, the engineers are working to miniaturize the time capsule, with the aim of creating a device measuring less than one micron. They are also investigating chemicals robust enough to handle subterranean heat, pressure and other factors.

Tang has a greater hope: “that this can inspire people to think of new ways they can process and record information.

—Marisa Messina, '16

Phones Aid Research

Too squeamish to donate blood, too broke to give money or too busy to volunteer? Stanford chemistry professor Vijay Pande offers a way for anyone with an Android phone to up their karma—an app that donates a smartphone’s downtime to research focused on cancer and other diseases.

The app is an extension of Pande’s long-running Folding@home network, which marshals the combined power of tens of thousands of computers to carry out incredibly intricate simulations of the ways proteins fold from generic ribbons of amino acids into 3-D shapes that carry out specific tasks. Understanding the origami-like processes—and the ways they go wrong—leads to a better grasp of diseases like Alzheimer’s, he says. But it’s slow going. A typical computer might take a full day to complete something nature performs in three nanoseconds.

Now Pande is adding the growing computational muscle of smartphones to the effort. The app runs when the phone is charging and connected to WiFi, but not in use. Once the phone is activated, the application slips the simulation to another phone to continue the work.

“There are a ton of people with really powerful phones, and if we can use them efficiently, it sets the stage for something really great,” Pande says.

The app will initially focus on how configurations of a particular protein affect different breast cancer medicines, allowing doctors to make better treatment decisions sooner. With 10,000 phones working eight hours a day, the project would take about three months, he says. A second project will investigate proteins associated with Alzheimer’s. Eventually the app could allow users to choose research most relevant to them.

The initial beta version of the Folding@home app is compatible with only Sony smartphones. A version for all phones running Android 4.4 and above is slated for release later this year.

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