## 1 Introduction  
A novel technique and a conceptual design of a mixing chamber were presented in the current study that could be used in future development of effective cold plasma devices for treatment of blood related syndromes such as leukemia. Plasma medicine research has been progressing very rapidly in recent years [1; 2; 3]. Cold atmospheric plasmas have shown significant potentials in various biomedical applications such as wound healing [4; 5], tooth bleaching [6], cancer therapy [7; 8; 9] and sterilization of infected tissues [10]. In recent years, cold atmospheric plasmas were explored for inactivating different microorganisms. They were found effective in decontaminating chicken skin and muscle inoculated with _Listeria imucua_[11]. Inhomogeneous inhabitation zones were generated in microcolonies by high flow rates of helium [12]. Furthermore, cold plasmas were found to show microbicidal and sporicidal effects but at the same time low toxicity for mammalian tissues [13]. Cold plasmas were also employed to treat the surface of polymers, including polyethylene with an ultra-high molecular weight used as joint replacements, and were additionally found able to enhance adhesion between the joint-replacement material and bone [14] as well as the wear performance of the polymer [15]. Therapeutic use of interaction between cold plasma and blood was successfully carried out [16]. Mixing between cold plasma and blood was also explored for treatment of large bleeding areas and for blood coagulation [17; 18; 19]. In relation, the viability and proliferation of human peripheral blood mononuclear cells upon exposures to atmospheric pressure argon plasma jets were studied, and significant cell damages for short plasma exposures were not observed [20]. The effect of cold plasma jet on wound healing was also comprehensively studied, and no significant effects from cold-plasma treatment were found on white blood cells, red blood cells, aspartate aminotransferase, alanine aminotransferase, blood urea nitrogen, or creatine contents [21]. More recently, possible use of non-thermal gas plasma as an alternative treatment scheme against leukemia was explored for the first time by [PERSON] et al., and it was found that the therapeutic effect of plasma on leukemia cells was not immediate (it has a delayed effect) and the increase in leukemia cell killing was achieved by increasing the contact time between the cold plasma plume and the cancerous human T-cell leukemia cells [22]. Furthermore, selective natural mechanisms of blood coagulation were triggered when blood samples were exposed to plasmas generated by non-thermal atmospheric pressure dielectric barrier (DBD) discharge at room temperature and pressure [23]. Moreover, the difficulty in directly treating blood with cold plasmas due to the coagulation was noted by [PERSON] et al., so injection of cold plasma solution into the blood around the tumor was explored by the authors, involving three different carrier gases, i.e., helium (He), argon (Ar) and nitrogen (N\({}_{2}\)) [24]. It was pointed out by [PERSON] et al. that cold plasma discharges had very low gas temperatures due to weak ionization rate for electron collisions and reactions [25]. The concentration of reactive species in the plasmas could be altered by the applied voltage [15]. In order to enhance the plasma chemistry while maintaining a low plasma temperature, very short voltage pulses (in the range from nanoseconds to microseconds) could be applied [22]. Moreover, the chemical reactions in plasmas were affected by the vibrational temperature, since the molecules were dissociated through their vibrational and electronic excitations [26]. On the other hand, the plasma characteristics were also affected by the plasma frequency since the very short lifetime of the charged particles could be comparable or even shorter than the applied pulse width. For example, in a previous study, the plasma frequency was set to be at 5 kHz and the pulse width was set at 0.50 \(\upmu\)s [22].