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Accueil > A propos du LPP > Communication > Actualités archivées > 2023 > Hang Yang defended his PhD "Multi-periodic and random mode of Atmospheric Pressure Plasma Jets and their interactions with liquid and biological targets"
Hang Yang defended his PhD "Multi-periodic and random mode of Atmospheric Pressure Plasma Jets and their interactions with liquid and biological targets"
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On March 2, 2023, Hang Yang defended his PhD "Multi-periodic and random mode of Atmospheric Pressure Plasma Jets and their interactions with liquid and biological targets".
Abstract :
Atmospheric Pressure Plasma Jets (APPJ) have been intensively studied and have numerous applications in plasma medicine such as wound healing or tumor reduction. In this thesis, three main features of APPJ are investigated : i) multi-periodic and random modes of propagation and the role of surface charges ; ii) the interaction between the APPJ and liquid targets ; iii) the modification of inert skin samples after plasma treatment.
A helium APPJ driven by 15 18 kHz sinusoidal voltage ignites multi-periodic self-triggered mode or random mode depending on the applied voltage, driven frequency, and inter-electrode gap distance. Most of the observed multi-periodic bullets operate every 2 or 3 sinusoidal periods. Such bullets show similarities with pulsed operating mode, having a jitter of smaller than 100 ns. The presence of an outer grounded electrode ring is a key parameter permitting the ignition of multiperiodic bullets ; it also enhances the propagation length up to 8 times. Fast imaging reveals that 2-3 self-triggered discharges occur in the gap region prior to ignition of the bullet in both positive or negative polarities ; this leads to an accumulation of charges beneath the ground electrode, locally enhancing the electric field. Time-resolved optical emission spectra at different locations and voltages show that most of the OH emission comes from the glow-like discharge in the gap region after the plasma bullet formation.
When interacting with a water target, the propagation of this APPJ shows similar multi- periodic modes and random modes. The H2O2 production rate is measured in water and it is concluded that the H2O2 is mostly produced inside the APPJ from the impurities disorbed from the gas tube’s inner wall.
Defrost pig skin is treated by the APPJ and analyzed by full-field Mueller polarimetric imaging (MPI). It is shown to modify the linear phase retardance and the total depolarization for higher plasma power and/or longer treatment duration. According to control groups, tissue alterations are primarily caused by the local heating concomitant to plasma-skin interaction above 0.5W/45 °C. This study aims to show that full-field MPI is suitable for fast and without-contact detection of skin microstructure modifications induced by plasma treatment.
Jury :
Reviewers :
Prof. Eric ROBERT
Prof. James WALSH
Jury members :
Prof. Anne BOURDON
Dr. Joao SANTOS-SOUSA
Dr. Angelo PIERANGELO
Supervisor :
Prof. Antoine ROUSSEAU
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