| AVS 60th International Symposium and Exhibition | |
| Plasma Science and Technology | Tuesday Sessions |
| Session PS-TuP |
| Session: | Plasma Science and Technology Poster Session |
| Presenter: | D. Ogawa, Chubu University, Japan |
| Authors: | D. Ogawa, Chubu University, Japan M.J. Goeckner, The University of Texas at Dallas L.J. Overzet, The University of Texas at Dallas |
| Correspondent: | Click to Email |
What if a liquid is injected directly into low-pressure plasmas? The current material processing with low-pressure plasmas (< 100 Pa) requires the gas-phase precursors in many cases. The limitation is sometimes irritating. The technique we have proposed, the direct liquid injection into low-pressure plasmas, enables liquids for plasma processing without applying any heat. Also, this technique enables the injection of solids through a liquid. For example, one could control the number of nano-particles in a film that is produced with a plasma to change the mechanical property of the film. Or, one could leave the clusters of solids on a substrate by evaporating a liquid off to print a three-dimensional structure. It is also fine that one uses heat-sensitive materials such as proteins, or even bacterias because the temperature of plasma processing is generally low. This technique definitely expands the possibility of material processing with plasmas.
With our best knowledge, not so many people researched the combination of direct liquid injection and low-pressure plasmas. Coppins suggested these kinds of plasmas to call as misty plasmas[i] [#_edn1] because one can consider that the droplets are another material state of particles. In contrast to dusty plasmas, misty plasmas can regulate the increase of particle temperature due to the droplet evaporation. Ward patented the configuration to realize the plasma processing in 2005.[ii] [#_edn2] However, our experiences showed that the configuration should create unstable plasma so that the process should be difficult.
This presentation shows the some investigations of the technique from some theoretical calculations and from the experimental observations. Our calculations shows that the evaporation time of droplets becomes half even at a plasma with 1010 cm-3 and 2 eV due to the contribution of three-body recombination on the droplet surface. On the other hand, our experimental results are far from the computational results because of our technical difficulties. Our time-resolved measurements of plasma density and optical emission intensity showed that a plasma dimmed due to the massive vapor at the first several milliseconds. This means that the plasma gives almost no contribution to the droplets’ evaporation because the transport time of vapor is much shorter than that of droplets. This result indicates that the control of initial vapor plays a role to realize this technique. In the poster, we will summarize these results shown above with recent progresses.
[i] [#_ednref] M. Coppins, Phys. Rev. Let. 104, 065003 (2010).
[ii] [#_ednref] Ward, US Patent No. 2005/0227018 A1.