Abstract
The design and the electric and emission characteristics of two handheld air plasma spray generators are presented. The plasma is generated by 60 Hz periodic discharges between two concentrically cylindrical electrodes. A ring magnet is used to rotate arc discharges, which sprays outward by an air flow. The rotation of arc discharges keeps the generated plasma in non-equilibrium state and at relatively low temperature (<55°C). The plasma effluent yet contains high energy electrons which dissociate molecular oxygen into atomic oxygen. The emission spectroscopy of the plasma plume reveals that the plasma effluent, which carries abundant atomic oxygen, extends from the cap of the plasma spray by about 25 to 30 mm. Tests on blood droplets and smeared blood samples revealed the effectiveness and mechanism of low temperature air plasma on clotting blood. Tests on oral pathogens show that air plasma creates a zone of microbial growth inhibition in each of six treated samples, including those of grampositive bacteria and fungi, and on a cultivating biofilm sample of Streptococcus mutans UA159. The medical applications of the air plasma sprays for 1) bleeding control, 2) wound healing, and 3) dental disinfection, are then illustrated and discussed. As animal models, pigs were used in the tests of stopping wound bleeding and post-operative observation of wound healing by this air plasma spray. The results show that the bleeding from a cut to an ear artery is stopped swiftly; this air plasma spray also shortens wound healing time to about half (from 14 days to 8 days) after stopping the bleeding of a cross cut wound in the ham area. In-vitro tests demonstrate that the plasma effluent of the spray can prevent the formation of dental biofilms and further eliminate the mature biofilms.
Highlights
Air plasma generated in an open environment makes it easy for practical applications; one of the current focuses is plasma medicine
The results show that bleedings of different wounds from a straight cut and a cross cut in the ham area, and a hole in a saphenous vein and a cut to an artery in an ear are all stopped swiftly; this air plasma spray shortens the wound healing time to about half after applying it for 10 seconds to stop the bleeding of a cross cut wound in the ham area
This plasma spray is non-equilibrium due to the following factors associated with the design and the operation, 1) the discharge is run in a periodic mode with a duty cycle of about 15/50%, rather than in a dc mode; 2) discharge occurs outside the electrodes and the gas flow increases the size of the arc loop considerably
Summary
Air plasma generated in an open environment makes it easy for practical applications; one of the current focuses is plasma medicine. Air plasmas carry chemically active species, such as molecular oxygen in metastable states and atomic oxygen These reactive species are capable of destroying a broad spectrum of chemical and biological warfare (CBW) agents [1,2,3,4,5,6,7,8,9,10,11] as well as activation of erythrocyte—platelet interactions for blood coagulation [12]. Argon plasma coagulator (APC) is operated in endoscope’s surgery for bleeding control [30,31,32] This device is a high-frequency mono-polar device used for noncontact thermal coagulation of tissue. In plasma coagulation applications for the external wounds, it will be desirable to have low temperature plasmas which open to the ambient and can cover a large area in the treatment. The medical applications of this plasma spray for bleeding control and wound healing are illustrated and discussed in Sections 4 and 5.
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