Chemical fuse makes cheap sensors

An electrical fuse is a simple, low-cost, single-use device that protects electrical circuits. When electrical current is too much for a system, the fuse material melts, breaking the circuit.

Researchers from the University of Durham in England have come up with a chemical fuse that works on a similar principle. The chemical fuse includes a thin layer of material that changes when it is exposed to a gas. The change is enough to permanently disrupt a flow of electrical current through the film.

The chemical fuse could eventually be used as a disposable sensor to monitor airborne pollutants. It could also be used as the sensing element of a cheap, disposable handheld personal breathalyser to monitor the concentration of alcohol in the blood.

The researchers constructed chemical fuses by using an inkjet printer to print a mix of a polymer that conducts electricity and polystyrene sulfonated acid. The sensitivity of the device is determined by the number of layers printed.

The researchers tested the device by exposing it to pulses of methanol or ethanol vapor. The initial exposure to the vapor rapidly changed the polymer, irreversibly decreasing the amount of current it could conduct.

The technique produces inexpensive, simple sensors that can be printed on a variety of surfaces, including flexible materials.

The chemical fuse could be ready for commercial use in two to five years, according to the researchers. The work appeared in the January 3, 2005 issue of Applied Physics Letters.