  Maintaining temperature is crucial in both daily life and industrial
settings, ensuring human comfort and device functionality. In the quest for
energy conservation and emission reduction, several contemporary passive
temperature control technologies have emerged, including phase change
temperature control, shape memory alloys, solar thermal utilization, sky
radiation cooling, and heat pipe systems. However, there is a pressing need for
more quantitative methods to further optimize temperature maintenance. With
advancements in theoretical thermotics and the emergence of thermal
metamaterials, it is clear that temperature fields can be precisely manipulated
by fine-tuning thermal and structural parameters. This review introduces three
innovative devices: the energy-free thermostat, the negative-energy thermostat,
and the multi-temperature maintenance container. All are grounded in the
principles of thermal metamaterials and primarily operate under conduction heat
transfer conditions. When compared with traditional technologies, the
unparalleled efficacy of thermal metamaterials in temperature management is
evident. Moreover, brief prospects present strategies to improve temperature
maintenance under convection heat transfer, thus expanding the application
spectrum of thermal metamaterials. This review concludes by spotlighting the
evolution and interplay of the aforementioned three devices, marking the
progression of thermal metamaterials from theoretical ideas to tangible
engineering solutions. These insights not only bridge the gap between applied
physics and engineering but also underscore the practical potential of thermal
metamaterials.
