3 research outputs found
A two-dimensional cold atmospheric plasma jet array for uniform treatment of large-area surfaces for plasma medicine
For plasma treatment of inanimate surfaces and living tissues in
medicine, it is important to control plasma–sample interactions and to mitigate
non-uniform treatments of usually uneven sample surfaces so that effectiveness
of application can be reproduced for different biological samples, relatively
independently of their varying surface topologies and material characters. This
paper reports a scalable two-dimensional (2D) array of seven cold atmospheric
plasma (CAP) jets intended to achieve these two important requirements as
well as to address the unique challenge of jet–jet interactions. While the CAP
jet array can be configured to interact with a biological sample in either a
direct mode (used with an in situ sample) or a remote mode (used as an
afterglow), this study focuses on the direct mode. Using a downstream planar
electrode as a sample model, the spatial distribution of reactive species and
electrons delivered by individual jets of the 2D CAP jet array attains excellent
uniformity. Specifically, the spatial variation over 100μs is 5.6 and 7.9%,
respectively, for wavelength-integrated optical emission intensity, and for atomic
oxygen emission intensity at 845 nm when the oxygen admixture is 0.5% of
the helium carrier gas. It is also shown that the highest emission intensity at
845 nm occurs at O2/He = 0.5% under the best jet–jet uniformity conditions for
O2/He = 0.3–0.7%. These results indicate the potential of 2D CAP jet arrays for uniform treatment and for effective control of jet–jet interactions. Furthermore,
spatial uniformity is accompanied by rich dynamics of jet–jet interactions and
jet–sample interactions. Of the honeycomb-arranged seven CAP jets, the central
jet is strongest in the negative half cycle, whereas the six surrounding jets
(of uniform strength) are strongest in the positive half cycle. These dynamic
features offer possible insights with which to better control jet–jet interactions
and plasma–surface interactions in future
Self-organized pattern formation of an atmospheric pressure plasma jet in a dielectric barrier discharge configuration
This letter reports the observation of self-organized patterns formed in a 29 mm wide atmospheric pressure plasma jet. By altering the gas flow rate and/or the applied voltage, the plasma jet is seen to have at least three different modes, namely, a diffuse-looking discharge, a self-organized discharge, and an unstable discharge with randomly occurring plasma channels. The self-organized discharge mode is characterized by several bright plasma channels embedded in a diffuse and dim plasma background. These plasma channels are regularly spaced from each other and their self-organized patterns are shown to evolve abruptly
Spatially extended atmospheric plasma arrays
This paper reports a systematic study of spatially extended atmospheric plasma (SEAP) arrays
employing many parallel plasma jets packed densely and arranged in an honeycomb
configuration. The work is motivated by the challenge of using inherently small atmospheric
plasmas to address many large-scale processing applications including plasma medicine. The
first part of the study considers a capillary–ring electrode configuration as the elemental jet
with which to construct a 2D SEAP array. It is shown that its plasma dynamics is
characterized by strong interaction between two plasmas initially generated near the two
electrodes. Its plume length increases considerably when the plasma evolves into a
high-current continuous mode from the usual bullet mode. Its electron density is estimated to
be at the order of 3.7 × 1012 cm−3. The second part of the study considers 2D SEAP arrays
constructed from parallelization of identical capillary–ring plasma jets with very high jet
density of 0.47–0.6. Strong jet–jet interactions of a 7-jet 2D array are found to depend on the
excitation frequency, and are effectively mitigated with the jet-array structure that acts as an
effective ballast. The impact range of the reaction chemistry of the array exceeds considerably
the cross-sectional dimension of the array itself, and the physical reach of reactive species
generated by any single jet exceeds significantly the jet–jet distance. As a result, the jet array
can treat a large sample surface without relative sample–array movement. A 37-channel SEAP
array is used to indicate the scalability with an impact range of up to 48.6mm in diameter, a
step change in capability from previously reported SEAP arrays. 2D SEAP arrays represent
one of few current options as large-scale low-temperature atmospheric plasma technologies
with distinct capability of directed delivery of reactive species and effective control of the
jet–jet and jet–sample interactions