Tiny Wireless Sensing Device Alerts Users to Telltale Vapors Remotely

October 5, 2014

A research team at the Georgia Tech Research Institute (GTRI) has developed a small electronic sensing device that can alert users wirelessly to the presence of chemical vapors in the atmosphere. The technology, which could be manufactured using familiar aerosol-jet printing techniques, is aimed at a variety of applications in military, commercial, environmental, healthcare and other areas.

Georgia Tech Research Institute researcher Xiaojuan (Judy) Song examines a functionalized nanomaterial-based sensor used to detect chemical vapors. This sensor integrates with a 5.8 GHz RFID tag and digitally communicates information back to the reader. (Georgia Tech Photo: Rob Felt)

The current design integrates nanotechnology and radio-frequency identification (RFID) capabilities into a small working prototype. An array of sensors uses carbon nanotubes and other nanomaterials to detect specific chemicals, while an RFID integrated circuit informs users about the presence and concentrations of those vapors at a safe distance wirelessly.

Because it is based on programmable digital technology, the RFID component can provide greater security, reliability and range — and much smaller size — than earlier sensor designs based on non-programmable analog technology. The present GTRI prototype is 10 centimeters square, but further designs are expected to squeeze a multiple-sensor array and an RFID chip into a one- millimeter-square device printable on paper or on flexible, durable substrates such as liquid crystal polymer.

“Production of these devices promises to become so inexpensive that they could be used by the thousands in the field to look for telltale chemicals such as ammonia, which is associated with explosives," said Xiaojuan (Judy) Song, a GTRI senior research scientist who is principal investigator on the project. "This remote capability would inform soldiers or first responders about numerous hazards before they encountered them."

The present prototype contains three sensors along with an RFID chip. Future devices for field use might contain a much larger number of sensors based on various nanomaterials — including carbon nanotubes, graphene and molybdenum disulfide — depending on the types of chemicals to be detected.

The RFID component in the GTRI device makes use of the 5.8 gigahertz (GHz) radio frequency, one of several radio bands reserved for industrial, scientific and medical (ISM) purposes. The GTRI component is believed to be the first RFID system that exploits this frequency. The advantage of 5.8 GHz technology is that it will let RFID tags be made extremely small — in the area of one centimeter square, said Christopher Valenta, a GTRI research engineer who is co-principal investigator on the project. He explained that the digital transmission of data from RFID-based sensors does a much better job than earlier analog techniques based on interpretation of radio-frequency waveforms.

The GTRI team successfully tested its prototype sensing system in a demonstration designed to resemble an airport checkpoint. The sensor array detected the targeted chemical despite emersion in a complex chemical environment, and the RFID component was able to transmit the sensors' readings.

The present GTRI prototype is semi-passive, so it requires power from an incoming signal beam in order to send data back to a remote reading device. However, future sensing devices might exploit ambient energy from solar or vibrational sources that would let them work at longer ranges with greater sensitivity.

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