By printing sensor circuits on boring old disposable rubber gloves, researchers have converted them into handy, low-cost screening tools for chemical threats and toxic pollutants. That means someday, security agents might swipe their gloved fingertip on a bag and quickly get an alert for traces of nerve agents and explosives on their smartphone.
The glove sensors, printed with special stretchable conductive inks, can detect a class of phosphorus-based chemical compounds used as chemical weapons and pesticides. In addition to weapons screening, the new lab-on-a-glove could be useful for food safety and environmental inspections, says Joseph Wang, a nanoengineer at the University of California, San Diego who developed the device reported in the journal ACS Sensors.
The military today has portable test kits to detect nerve agent vapors and liquids, including VX, which is suspected to have been used to assassinate Kim Jong Nam, half-brother of North Korean leader Kim Jong Un, in Kuala Lumpur in February. Testing involves exposing test strips and reading them using portable instruments such as chromatographs or spectrometers. A wearable glove sensor would make it even easier and faster.
Wang and his colleagues started with commercial purple medical exam gloves. On the thumb tip, they printed a thin carbon disk that would collect the chemical residue. The index finger has two electrodes printed with stretchable carbon ink. One electrode is soaked with an enzyme that binds to organophosphate compounds; the other serves as a counter electrode. Finally, they coated the circuit with a stretchy, insulating adhesive layer.
To test for nerve agents, the wearer rubs a surface with their thumb and then touches their thumb and index finger together. When organophosphate traces picked up by the thumb’s carbon pad come in contact with the enzyme on the index finger, this generates an electric current.
Wiggly connecting wires printed with stretchable silver ink send this signal to an adjustable ring-like bandage worn on the index finger. The ring, in turn, is wired to a small Bluetooth device on the back of the glove, which transmits data wirelessly to a mobile device.
Wearers testing the gloves were able to detect two different organophosphate drops on the surfaces of various fruits and vegetables, as well as on glass, wood, plastic, and steel. The gloves picked up contaminants at a concentration of 200 micromolar, comparable to today’s disposable paper-based nerve agent test kits. Wang says the gloves are reliable for “rapid field warning and screening applications,” and could be easily expanded to test for explosives.