## 4 Conclusions  
In this study, we developed a multi-gas temperature-controllable plasma jet that can generate plasma of various gas species at an arbitrary controlled temperature. A multi-gas temperature-controllable plasma jet was designed using CFD analysis with a TCF channel spiraled around the gas channel. The designed plasma jet was fabricated using metal 3D-printer technology. In the multi-gas temperature-controllable plasma jet, the stable generation of the plasma of nitrogen, oxygen, carbon dioxide, and argon was successfully achieved. The temperature of the plasma gas can be easily changed by controlling the temperature of the supplied TCF. Additionally, the gas temperature after plasma generation changed linearly by changing the TCF temperature. The gas temperature of the plasma was controlled between a minimum of \(3\)\({}^{\circ}\)C and a maximum of \(108\)\({}^{\circ}\)C by varying the plasma jet body temperature from \(-30\) to \(90\)\({}^{\circ}\)C. The gas temperature was increased by the plasma generation. The range of the temperature increase obtained for carbon dioxide, argon, nitrogen, and oxygen was \(31\), \(15\), \(41\), and \(34\)\({}^{\circ}\)C, respectively, when the plasma jet body temperature was \(20\)\({}^{\circ}\)C. These results indicate that the gas temperature control characteristics of plasma vary significantly depending on the gas species.  
It was shown that it is possible to design and fabricate plasma jets with a higher level of flexibility. A multi-gas temperature-controllable plasma jet of any shape can be fabricated for plasma applications in medicine, agriculture, and material processing. The use of multi-gas temperature-controllable plasma jets is expected to control the gas temperature of the plasma of various gas species and achieve stable treatment effects without damaging the treated object. In the future, we will study the gas species and temperature of the plasma for various applications such as hemostasis, disinfection, surface treatment, and plant genome editing.  
Conceptualization, S.M., T.T., Y.M., A.I., A.O.; methodology, Y.S., T.T., T.A., S.M., A.O.; validation, Y.S., T.A.; formal analysis, Y.S.; investigation, Y.S., S.M., T.A.; resources, Y.S., T.A., S.M.; data curation, Y.S., T.A., S.M., T.T.; writing--original draft preparation, Y.S.; writing--review and editing, S.M., T.T., Y.M., A.I., A.O.; Visualization, Y.S., T.A., S.M.; supervision, T.T., Y.M., A.I., A.O.; project administration, Y.M., A.I., A.O.; funding acquisition, A.I., A.O. All authors have read and agreed to the published version of the manuscript.  
This study was supported by JSPS KAKENHI (Grant Number: 20K07039) and the Cooperative Research Project of the Research Center for Biomedical Engineering, National Cancer Center Research and Development Fund (Grant Number: 31-A-11), TERUMO LIFE SCIENCE FOUNDATION (Grant Number: 18-II106).  
Not applicable.  
Data Availability StatementData is contained within the article.  
The authors would like to thank [PERSON] at the Design and Manufacturing Division, Open Facility Center, Tokyo Institute of Technology, for preparing the plasma jet parts. The authors would like to thank [PERSON] at the Kobe Design University, for useful discussions on plasma jet fabrication.  
The authors declare no conflict of interest.