Extec has developed a method of releasing printed elements from the substrate material. By this means, very thin structures only microns thick can be produced.

One application for the technique was to produce gas sensors.

The photos show two designs of Carbon Monoxide sensor, both designs are multillayer structures comprising a Platinum heater element over which is an interdigitated resistive element using Tin Oxide as the resistive medium. As carbon monoxide is absorbed into the tin oxide, so the resistance changes, which can be detected. The sensing occurs at a temperature of 400°C and this is where Extec’s process provides massive benefits. Because the structure is only 50um thick, it has virtually no thermal mass and can be heated to 400°C using very little power, in less than 100uS. Thus, if measurements are taken every few seconds, the sensor can be pulsed, giving huge energy savings; ideal for portable battery-operated devices.

The blue sensor shown is a differential sensor where one element has a coating to prevent carbon monoxide absorption. Thus, the differential reading is sensed and common-mode effects such as absolute temperature are nulled and a highly accurate sensor can be produced.