A portable device for large-sized microwave plasma jets

Large-sized, low-temperature plasma jets are used in a range of industrial applications from surface cleaning to solar cell texturing. The devices to produce these plasma jets are often large, making them unsuitable to many uses cases that require portability.

Zhao et al. developed a portable large-sized, low-temperature plasma jet device using coaxial cables. Previously, coaxial-based systems were limited to millimeter-scales. The novel design uses a miniaturized cylindrical resonant cavity with an inner conductor to amplify the electrical field. A coaxial cable delivers microwaves through a straight coil into the resonant cavity.

The cavity dimensions were optimized through modeling of the resonant frequency and electric field. The researchers tested the design with photography and thermometry using a mixture of argon, helium, and nitrogen gas. The design was able to produce a 9-millimeter-diameter atmospheric plasma plume with only 200 watts of power.

“Critically, our design delivered more than 90% microwave-to-plasma energy efficiency — aligning with theoretical predictions and confirming the design’s robustness,” said author Peng Zhang.

The researchers believe the device could be integrated into robotic arms or handheld tools for high-speed paint stripping of ships and aircraft, non-contact polishing of curved optics, and uniform texturing of solar cells. They plan to continue working on the device by including dynamic tuning systems to maintain efficiency during robotic use. Further work is planned to expand the reactive gases to accelerate the device’s use for paint removal and add in morphology-controlled etching for monocrystalline silicon surfaces.

“This synergy of scale, safety, and portability represents an advance toward practical industrial adoption,” Zhang said.

Source: “Design of a large-sized microwave plasma jet device based on coaxial cable transmission,” by Yingxin Zhao, Peng Zhang, Qiulin Wang, Shuangcheng Li, Xiuquan Cao, Jinwei Liu, Deping Yu, Physics of Plasmas (2025). The article can be accessed at https://doi.org/10.1063/5.0280602 .