Sensors printed on wetsuits detect explosives, other hazards

in a target threat or contaminant — which loses or gains electrons — then measuring the current output. The wearable microsystem provides a visual indication and alert if the levels of harmful contaminants or explosives exceed a pre-defined threshold. It does so by mixing different enzymes into the carbon ink layer before printing on the fabric. (For example, if the enzyme tyrosinase interacts with the pollutant phenol, the LED light switches from green to red.)

The release notes that the electronics are packed into a device known as a potentiostat that is barely 19 mm by 19 mm (the battery is stored on the reverse side of the circuit board.)

In the experiments described in the Analyst article, Wang and his team tested sensors for three potential hazards: a toxic metal (copper); a common industrial pollutant, phenol; and an explosive (TNT). The device also has the potential to detect multiple hazards. “In the paper we used only one electrode,” noted Wang, “but you can have an array of electrodes, each with its own reagent to detect simultaneously multiple contaminants.”

The researchers believe that neoprene is a particularly good fabric on which to print sensors because it is elastic and repels water. It permits high-resolution printing with no apparent defects.

The UCSD team tested the sensor for explosives because of the security hazard highlighted by the 2000 attack on the USS Cole in Yemen. The Navy commonly checks for underwater explosives using a bulky device that a diver must carry underwater to scan the ship’s hull. Using the microsystem developed by Wang and his team, the sensor printed on a wetsuit can quickly and easily alert the diver to nearby explosives.

Wang’s lab has extensive experience printing sensors on flexible fabrics, most recently demonstrating that biosensors printed on the rubber waistband of underwear can be used continuously to monitor the vital signs of soldiers or athletes. The researchers were uncertain, however, about whether bending the printed sensors under water – and in seawater – would still let them continue functioning properly.

In the end, even underwater, and with bending and other deformations, the sensors continued to perform well. “We still need to validate and test it with the Navy,” said Wang. “While the primary security interest will be in the detection of explosives, the Navy in San Diego bay has also detected large concentrations of toxic metals from the paint on Navy ships, so in principle we should be able to print sensors that can detect metals and explosives simultaneously.”

Wang’s work in flexible sensors grew out of twenty years of experience with innovations in glucose monitoring, ultimately in the form of flexible glucose strips that now account for a $10 billion market worldwide.

Work on the underwater sensors was supported by the Office of Naval Research.

— Read more in Kerstin Malzahn et al., “Wearable electrochemical sensors for in situ analysis in marine environments,” Analyst 136 (2 June 2011):2912-17 (DOI: 10.1039/C1AN15193B)