Close-Packed Arrays of Plasma Jets Emanating From Microchannels in a Transparent Polymer

Close-packed arrays of microplasma jets, propagating into atmospheric air with uniform plume length and luminosity, have been generated in cylindrical microchannels and characterized. Arrays as large as 8
$\times$
8 with a packing density of
$\sim\!\!160\ \hbox{cm}^{-2}$
have been demonstrated to date. Fabricated in a molded flexible polymer that is transparent deep into the ultraviolet
$(\lambda \gtrsim 250\ \hbox{nm})$
, microchannel devices
$ \lesssim\ 350\ \mu\hbox{m}$
in diameter generate plasma in He feedstock gas with a backing pressure of 760–900 Torr and flow rates up to 4.6 standard liters per minute. Chemical kinetics of the He
$(2^{1, 3}\hbox{S})$
and
$ \hbox{He}_{2}$

$(a^{3}\Sigma_{u}^{+})$
excited species interacting with laboratory air has been examined by optical emission spectroscopy. The maximum jet length for a 5
$\times$
5 array is
$3.8 \pm 0.2$
mm when the He backing pressure is
$840 \pm 20$
Torr. Relative to previous jet array designs, this technology increases the jet packing density by more than an order of magnitude and yet jet–jet interactions are not observed.