AbstractFoot ulcers constitute a major health problem for a rapidly growing number of people suffering from diabetes. Currently these wounds are difficult to treat, often become infected and are usually the first step to amputation. Treatment with non-thermal plasma may offer a solution to this situation. As a first step towards a suitable plasma source, a dielectric barrier discharge (DBD) device, which is named plasma plaster, is designed and characterised. The plasma plaster consists of a powered electrode and a polyimide barrier that covers the powered electrode. In the final application the targeted wound functions as secondary electrode. However, for the characterisation in the current study a stainless steel secondary electrode is used. A discharge is ignited in a 0.5mm air gap between the plaster and the secondary electrode by applying pulsed voltage to the plaster. Two plaster types are investigated: one has a solid plane electrode (the plane plaster) and the other has a square mesh electrode (the meshed plaster). It is hypothesised that through local electric field enhancement the meshed plaster may facilitate a more uniform discharge distribution when the secondary electrode is irregularly shaped. For both plasters a diffuse discharge is obtained rather than a filamentary discharge, which is attributed to the short discharge gap. Tomographic techniques are used to study the discharge distribution. For the plane plaster the discharge distribution in the gap is determined by the shape of the secondary electrode, while for the meshed plaster it is determined by the structure of the mesh. The gas temperature and reduced electric field are measured by optical emission spectroscopy. Gas temperatures of 325 K are measured for both plasters while operating at 6.5 kV and are considered safe for the application. A reduced electric field of 520 Td is found for the plane plaster, while a value of 600 Td is found for the meshed plaster. This increase of approximately 20% for the meshed plaster compared to the plane plaster is consistent with the local electric field enhancement predicted by electrostatic simulations. While further investigation is required to corroborate this final result, it suggests that the discharge distribution and reduced electric field can be controlled by adjusting the mesh pattern without undesirable side effects like an increase in gas temperature. This may open the way to tailor discharge properties for specific treatments.
|Date of Award||31 Jan 2015|
|Supervisor||Ana Sobota (Supervisor 1), Paulien Smits (Supervisor 2), Eddie van Veldhuizen (Supervisor 2) & Gerrit Kroesen (Supervisor 2)|
Characterisation of a dielectric barrier discharge with a square mesh electrode
van der Schans, M. (Author). 31 Jan 2015
Student thesis: Master