P-N switchable thermoelectric ionogels enabled by microphase separation for intelligent thermal sensing

Area of Science:

• Materials Science
• Thermoelectric Materials
• Ion Gels

Background:

• Ionic thermoelectric (iTE) materials are promising for thermal sensing due to high thermopower and low thermal conductivity.
• Conventional iTE materials have monotonic behavior, limiting their use in intelligent thermopiles requiring temperature-specific feedback.

Purpose of the Study:

• To develop iTE materials with switchable thermopower for multi-scenario thermal sensing applications.
• To design intelligent thermopiles and wearable devices with enhanced thermal sensing capabilities.

Main Methods:

• Synthesized thermoresponsive ionogels exhibiting a lower critical solution temperature phase behavior.
• Investigated the bipolar switchable thermoelectric properties induced by phase separation.
• Fabricated thermopiles by integrating p-n pairs in series for heat flux detection.

Main Results:

• Achieved bipolar switchable thermopowers ranging from +7.71 to -3.77 mV K^-1 in ionogels.
• Demonstrated nonlinear thermal voltages upon phase separation for intelligent over-temperature protection.
• Developed a prototype wearable device with 24 p-n pairs, yielding 0.22 V K^-1 total thermopower and 2 V m W^-1 heat flux sensitivity.

Conclusions:

• Nonvolatile ionogels with bipolar switchable thermopower are suitable for intelligent thermal sensing.
• The developed materials and devices show significant potential for advanced thermal sensing applications, including wearable technology.