Negative temperature coefficient metamaterial absorber for uniform microwave heating.

Microwave heating is widely used in daily applications but is fundamentally limited by non-uniform temperature distribution. Despite extensive efforts to manipulate energy distribution around materials, achieving uniform heating remains elusive due to the intrinsic inhomogeneity of electromagnetic fields. Here, we report a self-regulating solution that adaptively modulates the absorbance distribution using a Negative Temperature Coefficient (NTC) Metamaterial Absorber (MA). Distinct from electromagnetic field-shaping strategies, our approach intrinsically suppresses overheating in high-temperature regions and redistributes energy to cooler areas. We demonstrate, for the first time, that uniform heating-quantified by over 90% reduction in the coefficient of variation-can be achieved across diverse configurations, including planar, polyhedral, curved, and multiple objects, as well as under power variations spanning two orders of magnitude. This work not only provides a theoretical resolution to the longstanding challenge of non-uniform microwave heating but also opens new avenues for development and application of temperature-adaptive metamaterials.