March 2018    
  Heightened senses  
  Underground sensors provide real-time measurements and reveal interesting trends.  
  For as long as humans have been farming, they've been trying to figure out what's going on below ground. Soil is full of organisms, microbes, and chemicals that move and change constantly, and soil's complexity feeds into crop health and the earth's nutrient cycles in ways that aren't fully understood. But getting data has been a problem, since doing so has generally required taking soil samples and analyzing them in a lab, which is slow and expensive.  
  Recent advances in wireless data communications and the growing revolution of cheap portable sensors have made it possible for UChicago scientists, including Institute for Molecular Engineering professors Monisha Ghosh and Supratik Guha, to start a pilot program to take real-time soil measurements.  
  Their project, called the Thoreau sensor network, involved burying more than 30 sensing boxes at different locations around the UChicago campus. Each box contains four sensors that measure the soil's water content, salt, temperature, and water potential--the measure of how readily the soil holds or drains moisture. Twice an hour, a tiny radio transmitter with an antenna sends a burst of data to the receiver atop the William Eckhardt Research Center.  
  They used commercial sensors but had questions about how they might behave underground: Can the signals make it to the receivers above ground? (The team found that antennas buried six to eight inches deep could successfully transmit over distances of one-and-a-half miles, but wet soil appears to inhibit the signal.) What happens to the machinery during freeze-thaw cycles? (A few of the sensors didn't survive the winter.) Does the battery die faster? (Battery life has been the biggest issue so far.)  
  Measurements taken around Narsapur, a town on the bank of Godavari River, help to understand potential effects of agricultural runoff or fisheries found in this region. (Photo courtesy Supratik Guha)  
  As head of the Center for Nanoscale Materials at Argonne National Laboratory, Guha is interested in the sensor hardware. "What we would really love to do is to make a sensor that can measure soil nitrates," he said, in order to measure how much of the fertilizer that farmers use gets to the plants. It's thought that less than half of the nitrogen does; the rest likely washes off and pollutes rivers, lakes, and oceans.  
  Such networked systems, like Thoreau, could bolster environmental science, soil and plant science, and agriculture, which in turn would influence food security, human health, and ecology.  
  A complementary project is ongoing in India, testing the water quality of the Godavari River in southern India and how it reacts to weather, pollution, fishing, and general use. For this project, a boat carries a mobile sensing platform equipped with GPS along the river every few days, enabling scientists to map the river chemistry.  
  "Those results have been spectacular," Guha said. "We're seeing that dynamic mapping of river water quality can accurately help pinpoint and assess pollution sources."
--Louise Lerner
  Five more things about sensor tech  
The Array of Things is a networked urban sensor project collecting real-time data on Chicago's environment, infrastructure, and activity for research and public use--like a fitness tracker for the city.
Wearables, sensors, and monitors can help inform clinical trials, but these devices aren't perfect. The key is "to understand precisely how imprecise" they are.
A gene-edited patch of skin could one day be a glowing glucose sensor for diabetics.
A bandage-like "stretchable electronics" sensor helps measure stroke recovery.
Sensors made of DNA can investigate living cells.
  Keep cool  
  An artist's concept of the Parker Solar Probe shows the spacecraft approaching the sun. (Illustration courtesy NASA/Johns Hopkins APL/Steve Gribben)  
  As technology advances, sensors become increasingly sensitive, capable of detecting minute traces of substances or stimuli. But innovation has also increased insensitivity, producing sensors capable of withstanding exposure to harsh conditions.  
  Named after Eugene Parker, UChicago's S. Chandrasekhar Distinguished Service Professor Emeritus in Physics, the Parker Solar Probe launches late this summer on a mission toward the sun--getting closer than any spacecraft before. To collect data, the probe's sensors and instruments must survive extreme heat, velocity, and radiation.  
  The Parker Solar Probe seeks to answer questions such as why is the corona so much hotter than the surface of the sun? The probe should arrive at its closest approach in 2025, carrying a microchip with your name if you submit it before April 27.  
  In case you missed it  
Gut Feelings: Scientists study circadian rhythms and the microbiome.
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