Microwave heating of carbon materials for on-demand thermal patterning via tunable electromagnetic resonators

Recently, thermal manipulation in carbon materials has drawn much interest in multiple domains. Compared with existing conductive heating techniques, microwave heating has many advantages such as non-contact heating, fast and accurate temperature response, low energy consumption, etc. However, it is still challenging to realize real-time on-demand thermal manipulation in carbon materials with microwaves, due to the lack of effective control methods on electromagnetic (EM) properties. Here, for the first time, we report a solution to this problem by employing tunable EM resonators. Specifically, EM resonators with electrically tunable lumped elements were designed to couple microwave energy into the carbon material, realizing a pixel-controlled microwave heating performance. Through carefully designing the structure of the EM resonators, the local energy concentration on the tunable lumped elements was remarkably alleviated. Experimental results indicated that the microwave absorbance can be tuned from 12.1% to 99.6%, leading to a tunable heating rate ranging from 1.3 °C/min to 13.5 °C/min under fixed microwave power of 600 W. Moreover, a pixelated thermal manipulation was demonstrated through a thermal display of Arabic numerals. Our work may open new avenues for thermal manipulation in carbon materials and can be applied to complex thermal tasks such as customized materials processing, thermal display, deicing and defrosting, etc.