Enhanced treatment uniformity of chemical and biological liquids in cold atmospheric plasma system using gas bubble mixing

Abstract

Achieving uniform liquid treatment with cold atmospheric plasma (CAP) is vital for aqueous chemical and biological samples, especially for oxidation- and heat-sensitive substances such as proteins. However, attaining this goal remains a key challenge in the realm of plasma–liquid interactions. The difficulty arises from the limited liquid penetration of short-lived reactive species generated on the liquid surface, the heat produced when plasma forms in bulk liquid, and the instability of plasma bubbles generated in the liquid. Here, we report a gas bubble mixing approach to improve the uniformity of liquid treatment (ULT). The key idea is that the laminar wake created by a single bubble rising in a liquid serves as an efficient mixing mechanism that enhances ULT without compromising CAP stability. By integrating gas bubble mixing into a PLIMB (Plasma-induced Modification of Biomolecules)-based CAP–liquid reactor, we demonstrate a notable improvement in both ULT and treatment time for various liquid samples containing organic molecules. This strategy may be broadly extended to cold atmospheric plasma treatments of diverse functional material systems—such as drug-delivery exosomes, micelles, and plasma-aided surface-engineered nanoparticles—suspended or dissolved in liquids, enabling advances in plasma-aided processing of chemical and biological materials in their aqueous environments.