In 2007, when the Department of Homeland Security (DHS) issued a call for a sensor that could equip a smartphone with the ability to detect dangerous gases and chemicals, Ames Research Center scientist Jing Li had a ready response. Four years earlier, she led a team that wrote a paper on the use of carbon nanotube sensors for gas and organic vapor detection.

The NODE platform can be outfitted with an array of different sensor modules for detecting light, gases, temperature, motion, and more. It can store data or transmit it to a smart device using Bluetooth wireless technology.

She had been developing a device using single-walled carbon nanotubes that respond to various gases and compounds for use in NASA applications such as evaluating planetary atmospheres, detecting chemicals around rocket launch pads, and monitoring the performance of life support systems. What she still needed was a way for the device to “sniff” the air for samples, and a system that would allow it to interface with a smartphone.

Li approached George Yu of Genel Systems Inc., which could provide a very small sample collection system. That sampling jet proved too noisy, and Li and her team settled instead on a tiny fan. Then a separate contract for the cellphone interface system fell through. “That contract didn’t work out, so I asked George to do it — I know he is good at electrical circuit design,” Li said.

The team settled on the iPhone, which was new at the time, and Li convinced the program manager at DHS that the sensor should be a module attached to the outside of the phone, rather than a system built into the phone’s guts. “This is a very new technology, and there will be a lot of iterations. Making it interchangeable will make it easier to update,” she explained.

The modular design not only paved the way for future smartphone chemical sensors, but presaged the line of interchangeable, smartphone-savvy sensors Yu would commercialize a few years later after founding Variable Inc. in Chattanooga, TN.

Yu figured out how the sensor module could draw its power from the cellphone battery, and use the phone to digitally process the data it gathered and transmit it to a central location such as a cloud platform. Most of the design for the microprocessor, memory, communication protocol, back-end Web structure, data storage, and cloud technology he developed for NASA and DHS would later appear in Variable’s NODE wireless sensor platform.

The NODE Chroma color sensors let the user upload a custom color set and reference colors against a library of hues.

Ultimately, Li’s team outfitted each of 40 iPhones with a tiny chip containing 32 carbon nanotube sensors that react to potentially harmful chemicals, as well as volatile organic compounds. Most of the phones have been delivered to DHS, and are being tested by technical first responders and trained personnel. If firefighters arrive at a scene involving a toxic gas leak, for example, the device can let individuals know how far into the area they can safely go, and the collective data from multiple firefighters carrying the technology can map the extent and boundary of the chemical hazard. All this is accomplished without requiring anyone to carry an additional device other than the cellphone.

Building on the integration system he developed for the DHS Cell-All initiative, Yu developed his NODE platform — a cylinder not much bigger than a man’s thumb that can transmit data from sensors to a smartphone or other smart device, and that also has its own memory port capable of storing data to be uploaded to any computer. Unlike the sensor developed for DHS, NODE operates independently of the cellphone and transmits the data to the phone or other device using Bluetooth wireless technology.

Variable converted off-the-shelf sensors, such as infrared thermometers, color referencers, motion sensors, and barcode readers, into interchangeable modules that can be snapped onto either end of NODE, so it can use two modules simultaneously. There is a module for carbon dioxide detection and another that senses chemicals and gases. Another module measures ambient light, room temperature, humidity, and barometric pressure.

The product line went on the market in 2012, and by summer of 2014, it was already in its second generation, NODE+, which is faster, uses less power, is more durable, has more memory, and is compatible with Android devices as well as Apple smart devices.

A company that deals with paints or other color-specific products can use one of the Chroma sensors for quality control, just as one that deals with food can use the infrared thermometer or thermocouple probe for temperature assurance. Since each NODE can house two sensors, someone doing temperature control can take a temperature reading and then flip the device around to scan a product barcode that would show to which product the reading applies.

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