Experimental–Numerical Characterization of Cold Atmospheric Pressure Plasma Jet for Biomedical Applications Using Moiré Deflectometry

Authors
Erfan Ghane Sheykh Abadi 1
Heydar Izdanshan 1
Mahmoud Dehghan 2
Fatemeh Jamal 3
Mohammad Haqparast 4
Lily Darvish 4
1 Department of Optics and Laser Physics, Islamic Azad University, Shiraz, Marvdasht, Iran
2 Department of Radiology, Faculty of Paramedicine, Hormozgan University of Medical Sciences, Hormozgan, Iran
3 PhD student in Optics and Lasers, University of Zanjan, Zanjan, Iran
4 Department of Radiology, Faculty of ParaMedicine, Hormozgan University of Medical Sciences, Bandar Abbas, Iran
Abstract
Introduction: Cold atmospheric pressure plasma jets (CAPJs) have shown significant potential for biomedical applications due to their non-thermal nature and high production of reactive species. In this study, we assessed the experimental-numerical characterization of CAPJs for using in biomedicine using Moiré deflectometry.

Materials and Methods: The electron density and refractive index distributions measured in the original Moiré deflectometry experiment were used as input data. A numerical model was implemented in MATLAB to reconstruct the continuous axial profiles n_e (z)and Δn(z) based on exponential fitting of the experimental points. The plasma was generated using a helium jet at atmospheric pressure, with an inner quartz tube of 1 mm diameter and a central stainless-steel electrode of 0.3 mm diameter. The applied voltage and gas flow rate were 5 kV-10.2 kV (18 kHz AC) and 0.5-2 L/min, respectively. Refractive index variation was calculated using the empirical relation is, n-1=C_1 p/kT-C_2 N_e, where C_2=1.9292×10^(-8) (cm³). The medically relevant parameters—plume length (for n_e≥10^18 ' ' m^(-3)) and the RONS-proxy (integral of n_e (z))—were then derived from the reconstructed profiles.

Results and Discussion: The numerical reconstruction successfully reproduced the experimental Moiré results, showing an exponential decay of n_ealong the plasma axis. At 10.2 kV and 2 L/min, the maximum n_enear the nozzle was 3.1×10^19 ' ' m^(-3), decreasing to 1.3 × 10^19 ' ' m^(-3)at 16 mm. The effective plume length, defined as the distance where n_e≥10^18 ' ' m^(-3), was about 5.6 mm for high-power mode and 3.2 mm for low-power mode. The change in refractive index (Δn) derived from the Moiré analysis exhibited values of the order of 10^(-6), confirming the optical sensitivity of the plasma region close to the nozzle. From a biomedical perspective, the obtained electron density range (10¹⁸–10¹⁹ m⁻³) is sufficient to produce reactive oxygen and nitrogen species (RONS) while maintaining gas temperatures below 50°C—safe for biological tissue exposure. Hence, the helium plasma jet characterized in the original experiment can be directly utilized for plasma medicine applications such as surface sterilization, cell stimulation, and wound treatment.

Conclusion: The combination of Moiré deflectometry and numerical reconstruction provides a powerful approach to link plasma diagnostics with biomedical functionality. The reconstructed axial profiles reveal that the plasma jet operates within the safe and effective range for biological applications. The model also offers a predictive tool to optimize voltage and gas flow parameters for future plasma medicine studies.

Keywords
Biomedical Application
Cold atmospheric plasma
Electron density
Moiré deflectometry
Refractive index