Guided-wavelength-controlled dynamic microwave heating in a near-cutoff waveguide

Abstract

Microwave heating due to microwave–matter interactions has been widely used in various materials and processes. However, a key obstacle to the use of microwave heating is the lack of desired control over the location of the antinodes and nodes of microwave fields, resulting in undesirable overheating or non-uniform heating. Here, we report novel dynamic microwave heating based on the guided-wavelength-controlled relocation of the antinodes and nodes using a near-cutoff waveguide, where the frequency-dependent guided wavelength is at least 10 times longer than the free-space wavelength and changes dozens of times larger than in free space. The dynamic microwave heating is demonstrated even in an in-cutoff waveguide since a dielectric sample, to be heated, drives the waveguide out of the cutoff condition. Specifically, the heating position in a sample moves significantly under the manipulation of dynamically rearranged antinodes with only ~ 2% frequency change. Thus, selective microwave heating at a desired part in the sample is realized in a narrow frequency band, subsequently leading to uniform heating by changing the heating position properly.