Plasma Chemistry and Plasma Processing, Vol.40, No.5, 1253-1265, 2020
Localized Electric Field Enhanced Streamer Cold Plasma Interaction on Biological Curved Surfaces and Its Shadow Effect
Combining dielectric barrier discharge (DBD) structures into conventional point-to-plane corona discharge structures indicates the underlying mechanism of modifications from atmospheric streamer cold plasma (SCP) on curved surfaces. We performed SCP treatment on cabbage and rice seeds as biological samples due to their curved and well-defined surfaces. The results indicate that under given treatment conditions, there is no difference between their surface modifications for the top and bottom (shadow) seed surfaces as indicated from the wettability enhancement [water imbibition (WI) and apparent contact angle (ACA)]. The WI enhancement for the treated cabbage and rice seeds increased significantly by similar to 90% from the intrinsic surface. Finite element method simulations demonstrate two regions with highly-localized electric field (E-field) up to similar to 10(5) V/cm between the electrodes. The first region is around the tip edge and enables SCP while the second region is underneath the seed surface, which becomes important to modify the shadow surface via DBD plasma. Such a high E-field allows gaseous breakdown and provides electro-chemical and -physical reactions on similar to 95% of the curved sample surfaces. The SCP provides reactive components to modify the top seed surface while the bottom is modified via DBD. Moreover, samples with higher relative permittivity varied based on the crop types, moisture content, and the operational frequency directly increase the E-field distribution below the seed surface, creating a greater DBD plasma formation and overall surface activation. We also demonstrate the SCP has a potential for germination enhancement and is fundamentally suitable for translation into large-scale applications.
Keywords:Streamer cold plasma;Nanoscale surface modification;Gas discharge;Seed germination enhancement;Corona discharge;Oryza sativa