A thermoelastic device comprising an expansive element is disclosed. The expansive element is formed from a material, which is preselected on the basis that it has one or more of the following properties: a resistivity between 0.1 μΩm and 10.0 μΩm; chemically inert in air; chemically inert in the chosen ink; and depositable by CVD, sputtering or other thin film deposition technique.