What Is Cold Plasma?

As a highly engineered state of matter, cold plasma's unique components have made it an indispensable tool across various technological and industrial fields. Its defining feature is the ability to generate highly reactive chemical species while maintaining a low overall temperature, preventing thermal damage to sensitive materials. This is achieved through the precise control of its core components, including charged particles, reactive species, and electromagnetic fields. The ability to control components has led to transformative applications in fields such as healthcare, including advanced sterilization and targeted medical treatments. Furthermore, its significant impact on environmental sustainability, food security, and agriculture positions it as a cornerstone technology. Ultimately, cold plasma's distinct combination of low-temperature operation and high reactivity is shaping the future of multiple industries.

The most unique characteristic of cold plasma is its state of thermal non-equilibrium, where its free electrons are highly energetic and chemically reactive while its heavier ions and atoms remain at or near room temperature. This fundamental duality is its transformative advantage, allowing it to separate powerful chemical reactivity from high temperatures—a feat impossible for hot or warm plasma. Because it operates without significant heat, it can function with precise control, safely interacting with delicate materials such as living tissue, polymers, and electronics without causing thermal damage. Its collective behavior and responsiveness to electric fields enable the precise and uniform delivery of these reactive chemical species where they are needed most. These distinct properties unlock revolutionary applications that demand both safety and effectiveness, including the sterilization of wounds in biomedicine, the enhancement of seed germination in agriculture, and the modification of advanced materials.

The classification of plasma, particularly cold plasma, is a critical process that hinges on two distinct yet interconnected stages: characterization and categorization. The first stage, characterization, involves identifying and measuring the fundamental parameters of a plasma to provide the detailed data necessary for its control and manipulation. This data then enables the second stage, categorization, which systematically groups plasmas based on shared attributes, such as temperature and discharge type. By following this structure—from detailed measurement to systematic grouping—researchers and engineers can precisely align specific plasma types with applications in medicine, manufacturing, and environmental science, effectively bridging foundational research with practical innovation. 

The controlled generation of artificial plasma is fundamental to many modern technological applications. A key area of development is cold plasma, which is engineered for use in heat-sensitive environments such as medicine, biotechnology, and surface sterilization. The production and control of this state of matter depend on specific methods, power sources, and equipment. Critical factors, such as gas composition, pressure, and electrode design, directly influence the resulting plasma's characteristics. Persistent challenges in the field include improving energy efficiency, maintaining stability, and achieving industrial scalability, though ongoing advancements are poised to expand the capabilities and impact of cold plasma technology. 

Recent advancements in cold plasma have garnered significant attention, resulting in innovations across various scientific and industrial fields. Effectively developing these technologies relies on a practical classification of the different plasma discharges that can be generated. The most common approaches categorize these cold plasmas based on their reactor design and distinct discharge characteristics. These factors, in turn, directly influence the operational stability, efficiency, and uniformity of the plasma. Understanding this framework is essential for optimizing system performance for specific tasks. This knowledge ultimately enables the customization of non-thermal plasma technologies for a diverse range of applications.

Artificial plasma technology is categorized into three classifications: cold, warm, and hot, each with unique applications and limitations. Among these, cold plasma has become a prominent focus of innovation due to its non-thermal properties and high reactivity. This makes it particularly suitable for sensitive applications in medicine, surface modification, and environmental remediation. While warm and hot plasmas fulfill more energy-intensive roles, the advancement of cold plasma faces its own set of challenges. These limitations, including scalability and significant initial investment, mirror the broader hurdles confronting plasma technology as a whole. Despite these obstacles, the adaptability and potential of cold plasma continue to drive its development across critical industries.

Artificial plasma represents a groundbreaking advancement across various industries, though much of its potential is still being explored, validated, or commercialized. Its ability to ionize gases and create charged particles opens new possibilities in various fields, including medical treatments, industrial manufacturing, energy production, environmental solutions, aerospace technologies, and electronics. As research continues to unveil its capabilities and optimize its applications, the versatility of artificial plasma positions it as a powerful tool for solving complex challenges, enhancing efficiency, and potentially improving outcomes in these sectors. 

Plasma-activated liquids (PALs) are created when conventional liquids are treated with plasma, generating a potent mixture of reactive chemical species. This process fundamentally alters the liquid’s chemistry, causing measurable changes like increased acidity and a higher oxidation-reduction potential. The final properties can be precisely engineered by controlling the plasma generation method and the base liquid, which can range from water and saline to oils and juices. This versatility allows for the creation of specialized PALs engineered for specific tasks. As a result, these liquids are emerging as powerful, eco-friendly tools with broad applications in fields like biomedicine, agriculture, and environmental remediation. 

Plasma-activated water (PAW) has become the most extensively studied and widely used plasma-activated liquid (PAL), offering eco-friendly and multifunctional solutions across healthcare, agriculture, environmental remediation, and food safety. Generated through direct plasma treatment or plasma-gas interactions, PAW is enriched with reactive oxygen species (ROS), reactive nitrogen species (RNS), and other plasma-induced molecules, which give it unique properties like acidification, high oxidation-reduction potential (ORP), and increased electrical conductivity. These characteristics distinguish it from other reactive liquids, such as ozone water, and make PAW customizable for specific applications. Its antimicrobial activity, pollutant degradation potential, and ability to enhance plant growth and promote wound healing highlight its versatility. Different production methods, such as liquid-phase plasma (LPP) and gas-phase plasma diffusion (GPPD), influence its reactive species composition and efficacy. At the same time, factors like activation time and storage conditions impact its stability. Overall, PAW exemplifies the transformative potential of plasma technologies as a sustainable and impactful tool across multiple industries.