Optical spectroscopy study for pulsed frequency powered atmospheric He plasma

The atmospheric plasma has a great advantage over its vacuum counterpart for surface treatment such as cleaning and coating in its much less destructive nature. This nature makes the atmospheric plasma to function more like an ion carrier rather than a reaction hub for processes like ionization, dissociation, and excitation. The less destruction also preserves the integrity of molecular microstructures before deposition. Such a condition is particularly necessary for depositing macromolecules such as proteins, DNA/RNA in biomedical applications. In this study, we investigate the effects of the pulsed frequency of power and gas flow rates on the chemical compositions and morphology of atmospheric He plasma generated by a customized plasma system. Using an optical emission spectrometer, the spectra of He plasma in the air were quantitatively assessed for cases of different pulsed frequencies and He flow rates. In order to evaluate the capacity of He plasma, treatments on liquid (de-ionized water) and soft solid surface (spin-coated lactic acid films) were performed by direct contact. For the case of de-ionized water, the interaction between plasma and water is found to generate amount of OH radicals following the increase of pulsed frequency. For the case of spin-coated lactic acid films, the OH radicals generated by the plasma can cause the destruction of existing OH bonds in lactic acids to form water molecules during plasma treatment.