A drug delivery pump includes a dosing chamber (16) for delivering a substance (18) therefrom, pushing apparatus, and a thermal energy source (14) arranged to cause a sufficient change in temperature in a portion of the pushing apparatus so that the pushing apparatus imparts a pushing force against the substance to cause the substance to be delivered from the dosing chamber. A controller (90) controls delivery of the substance from the dosing chamber. A thermal insulator (24) thermally insulates the substance in the dosing chamber from the thermal energy source.
