Plasmas display significant advantages over wet chemical methods for surface modification of polymers as well as other materials. Many commercial plasma processes perform surface functionalization, graft and plasma polymerization, cleaning, and etching of a large variety of substrates. Most of these processes are conducted in vacuum systems. Non-thermal atmospheric pressure plasmas offer the obvious advantages of eliminating the cost and complexity of operating under vacuum. With its enormous advantage in plasma density increase over other atmospheric NTPs, APPJ technology has the potential to revolutionize this area.

APPJ surface treatment can be done in either a downstream or an in-situ mode. Typically, the in−situ approach is preferred, because it requires less gas flow and consumes less power. The downstream process requires a greater gas flow to carry a flux of reactive species from the jet to the substrate surface. In the in-situ process, the reactive species are formed in proximity to the substrate surface, and gas flow is needed only to replace the active species that are consumed in the chemical reactions on the surface. Helium recycling can mitigate gas consumption for both the downstream and the in-situ modes of operation.

Applicable for a Variety of Substrates
APJeT's technology can be conducted on flexible substrates or objects of regular shape, generally flat or cylindrical. The substrates can be electrically conductive or insulating. In contrast to other atmospheric NTPs, the APPJ technology allows use of conductive substrates because they function as the ground electrode. Therefore, the thickness of the substrate is not limited. If the substrate is insulating, it should generally be less than 0.25 inches thick, or else a downstream treatment should be considered.

The Atmospheric Pressure Plasma Reactor (APPR III) technology enables in-situ treatment of flat or flexible substrates. Substrates up to 12 inches wide are placed on the movable ground table and shuttled through the plasma at a controllable rate by a motor drive. Similar electrode designs have been built as large as 72 inches by 9 inches.

This system has been used for cleaning, etching, surface treatment, and plasma polymerization on numerous substrates, including:

• PTFE films
• PET films
• LDPE films
• Metals
• Glass
• Silicon wafers
• Variety of textiles

For example, the APPJ technology has been used to defluorinate a PTFE surface, making the inherently hydrophobic surface wettable. This capability is critical for printed circuit board applications, as well as adhesive tapes. Plasmas are being marketed for this application as an environmentally sound alternative to the conventional wet-chemical, sodium-etch approach. However, the traditional atmospheric NTP methods are generally too slow to be economical. APJeT has demonstrated that a one-second APPJ exposure achieves defluorination and wetting levels, as determined by XPS analysis and water contact angle, which require several minutes using DBD reactors.

a) Schematic:

b) Photograph of Actual Unit: