Provided is a thermo-pneumatic actuator which can include a substrate, an insulating layer formed on the substrate, a working fluid disposed in a fluid chamber, an ink chamber separated from the fluid chamber by at least a portion of the device layer comprising an actuatable membrane, and a heating element formed between the insulating layer and the fluid chamber. A boiling point temperature of the working fluid in the fluid chamber is in the range of greater than about 100° C. to about 500° C.