Abstract: A temperature indicator includes a compound comprising an ionic fluid disposed in contact with an absorbent medium at a first location. Detection circuitry is coupled to the absorbent medium at a second location spaced apart from the first location. Communications circuitry is coupled to the detection circuitry and is configured to output a value indicating an actuation state of the temperature indicator indicated by the detection circuitry. Responsive to the temperature indicator being exposed to a temperature exceeding a temperature threshold, the compound migrates along the absorbent medium from the first location toward the second location. The detection circuitry is configured to indicate the actuation state based on a presence of the compound at the second location.

Abstract: The invention provides a colour change composition containing an electron donating organic colouring compound, an electron accepting compound and a compound of formula (I): wherein E is an ester linkage O—CO or —CO2, R is independently selected from an optionally substituted linear or branched alkyl group, alkenyl cycloalkyl group, alkenyl group, alkoxy group, aryl and alkylene aryl group having from 6 to 22 carbon atoms; Y1 Y2 X1 and X2 are independently selected from hydrogen, R?, —OR? and halogen; wherein R? is independently selected from an optionally substituted linear or branched alkyl group, alkenyl group, alkoxy group, aryl group and an alkylene aryl group; having from 5 to 22 carbon atoms; r and p each represent and integer from 0 to 3. The compound of formula (I) and compositions of the invention are useful in providing a colour change effect, in memory compositions and visual indicators, particularly in security and healthcare applications.