# Anti-Bacterial Action of Plasma Multi-Jets in the Context of Chronic Wound Healing
## 3 Results  
### Multi-jets Characterization  
The power coupled to, and the current flowing across each of the individual 52 secondary jets with the multi-spot applicator were not measured in this work, but it is speculated that they are more or less evenly distributed in between each of these secondary jets. Indeed, while not specifically assessed in this work, the longtime exposure up to 5 to 10 min of the agar sample never revealed any local melting, ablation or deformation of the sample at the position of the plasma spots or in the zone in between them. This is an indication that neither severe temperature increase nor dramatic ion bombardment occur during multi-jets exposure. Nevertheless, Figure 5 reveals that the secondary jets generated from the two inner rings of the multi-spot plasma applicator exhibit a higher visible light intensity. A primary reason for this lies in the secondary jets mechanisms. Indeed, the secondary jets are generated after the primary jet ignited in the upper section of the applicator splits in the first channels distributed along the first inner ring [45; 46]. Then a second splitting of the remaining ionization wave propagating in the upper section from the first to the second ring occurs and generates the secondary jets emerging from the second ring channels. The same process repeats for the third and fourth series of multi-jets emerging from the periphery of the applicator. During these splitting processes, part of the power is carried by the secondary jets, the rest being transported in the plasma developing in the upper part of the applicator before the next splits occur in the large diameter ring. A second likely reason for this higher intensity of the inner secondary jets is that even if the upper section was empirically designed to allow for a homogenous gas flow distribution in the channels where the secondary jets are generated, it is suspected that this gas flow is lower in the peripheral holes than in the center holes.  
Figure 5: Photograph of the multi-spot plasma applicator delivering the secondary multi-jets in ambient air.  
Figure 6a presents the current measurements performed with the use of a grounded metallic target set 10 mm away from the low voltage applicator delivering 4 secondary jets. By using a dielectric foil set to impede either none, one, two, and three of the secondary jets to impact the target, Figure 6b demonstrates that each one the secondary jets carry on a fourth of the whole current measured when the four jets impinge on the target.  
Figure 6b illustrates the operation of this four multi-jet device exposing the agar sample [49] enriched with potassium iodide. The potassium iodide is used as an indicator for the delivery of reactive species by the multi-jets [44,50]. Is it shown that for a 60 s plasma exposure, the reactive species are delivered as four spots on the sample while for a longer exposure of 240 s, the reactive species are detected almost all over a disk defined by the edges of the four multi-jet assembly. The same results were achieved for applicators generating 9 and 13 secondary jets distributed over a disk 50 mm in diameter.