Combined Continuous Wave and Pulsed Plasma Modes: For More Stable Interfaces with Higher Functionality on Metal and Semiconductor Surfaces

A novel approach to producing improved bio‐interfaces by combining continuous wave (CW) and pulsed plasma polymerization (PP) modes is reported. This approach has enabled the generation of stable interfaces with a higher density of primary amine functionality on metal, ceramic and semiconductor surfaces. Heptylamine (HA) was used as the amine‐precursor. In this new design, a thin CW PPHA layer is introduced to provide strong cross‐linking and attachment to the metal or semiconductor surfaces and to provide a good foundation for better bonding a pulsed PPHA layer with high retention of functional groups. The combined mode provides the pulsed mode advantage of a 3‐fold higher density of primary amines, while retaining much of the markedly higher stability in aqueous solutions of the continuous mode. Pulsed plasma polymerization is known to give better retention of the monomer structure, and consequently, more of the desired functional groups on the surface. However, continuous wave plasma produces a strong highly cross‐linked polymer with much better attachment to inert surfaces, such as metals. Combining the two modes imparts the best characteristics of each, giving markedly higher stability in aqueous solutions with higher density of primary amines.