The invention pertains to flexible devices used for zero-heat-flux, deep tissue temperature measurement, especially to disposable temperature measurement devices. Such a device is constituted of a flexible substrate with a plurality of contiguous sections. An electrical circuit is disposed on a side of the substrate. The electrical circuit includes first and second thermal sensors disposed, respectively, on first and second substrate sections. A heater trace is disposed on the first substrate section with the first thermal sensor. The first and second sections are folded together to position the first and second thermal sensors therebetween, and a flexible insulator disposed between the folded-together first and second sections maintains the first and second thermal sensors in a spaced-apart relationship.