Plasma sources for biomedical applications: Past, present, and future

Plasmas have been widely used for various applications such as etching, material treatment, and biomedicine^1-7. On the other hand, unlike other plasma sources, the plasma sources used for biomedicine must meet some strict requirements including the safety issue, electromagnetic regulation, and so on. In this paper, firstly, an abbreviated history of plasmas used for biomedicine is presented. Secondly, traditional plasma sources used for plasma medicine are briefly introduced. Thirdly, main focus of the paper on current plasma sources for biomedicine is discussed, which includes various types of atmospheric pressure plasma jets (APPJs), the physics and chemistry of APPJs. Fourthly, several commercial plasma biomedicine devices are reviewed. Finally, the future challenges and opportunities of plasma sources for biomedical applications are envisaged. One of the example is, when the diameter of the widely used plasma jets goes from the current millimeter range to micrometer or even nanometer range, it can not only be used for single cell treatment⁸, but also the characteristic of the plasma will be significantly different from the idea plasma because the dimension of the plasma could be close to the thickness of sheath, which is attractive for fundamental study of plasma⁹.