A colorimetric sensor that provides a direct visual indication of chemical contamination was developed. The detection is
based on the color change of the reflected light after exposure to a gas or a liquid. The sensor is a combination of a
chemically sensitive dye layer and a subwavelength grating structure. To enhance the perception of color change, a
reference area sealed under a non-contaminated atmosphere is used and placed next to the sensor. The color change is
clearly visible by human eyes. The device is based on photonic resonant effects; the visible color is a direct reflection of
some incoming light, therefore no additional supplies are needed. This makes it usable as a standalone disposable sensor.
The dye thin film is deposited by Plasma enhanced chemical vapor deposition (PECVD) on top of the subwavelength
structure. The latter is made by combining a replication process of a Sol-Gel material and a thin film deposition. Lowcost
fabrication and compatibility with environments where electricity cannot be used make this device very attractive
for applications in hospitals, industries, with explosives and in traffic.
A new gas sensor was developed to enable visual indication of a contamination by specific gases like NO<sub>2</sub>, SO<sub>2</sub>, UV, etc. The sensor works with a combination of subwavelength structures and specific active dye thin film layers. The objective is to use the optical changes of the dye thin films after exposure and a custom designed subwavelength structure, a suited combination of both will produce a strong color change.
The indication should be visible for the human eye. To enhance this visual aspect, we used a reference sensor sealed into a non-contaminated atmosphere.
This work was realized within the PHODYE STREP Project, a collaboration of the 6th Framework Program Priority Information Society Technologies.