Visualizing thermal distribution through hydrogel confined ionic system

Effective thermal regulation has shown great impacts on tremendous aspects of our life and manufacture. However, the invisible nature of thermal field brings us inconvenience or even security hazard. Herein, we present a method to visualize thermal distribution with the aid of a thermally active material. An ionic liquid with lower critical solution temperature is mixed within hydrogel to demonstrate a hydrogel confined ionic system (HCIS). This particular system turns turbid as the temperature exceeds an established temperature threshold, which is adjustable through applying different concentrations of HCl or NaCl. The system offers straightforward images of the spatial thermal distribution whether simple or sophisticated, which is fully in line with computational simulation. The system is further demonstrated with great promise for the application in fire warning to lower the threat induced by electrical failure. The HCIS opens a practical avenue to visualize thermal distribution and improve our thermal regulation efficiency.