Temperature sensor based on liquid phase transition

A temperature sensor with alarm function based on the temperature-driven liquid phase transition has been designed and fabricated. This chamber-like temperature sensor device consists of a highly stretchable CNFs/ecoflex film as the deformable lid and an aluminum box-like base. 1 mL of water was sealed in the “chamber” and it can vaporize rapidly to induce deformation in the CNFs/ecoflex film when environment temperature reaches its boiling point, resulting in a dramatic increase of resistance in the CNFs/ecoflex film. This temperature sensor shows a high sensitivity of -0.84%/^oC below the boiling temperature of the liquid sealed in the box. Closed to the boiling temperature, significant resistance change is measured, indicating the potential as an alarm system. The response temperature could be controlled by changing the liquid inside the chamber. The cyclic tests indicate good durability. Owing to the advantages of low cost, simple fabrication, and good repeatability, this temperature sensor device has great potential for application as a thermistor or a temperature alarm in food and materials industry.