Using low-pressure plasma for Carthamus tinctorium L. seed surface modification

Low-pressure RF argon gas discharge was used for surface modification of Safflower (Carthamus tinctorium L. semen) to increase the germination rate and activity and reduce the germination time. The results showed that plasma-treated C. tinctorium L. semen has 50% higher germination rate, 100% increase in the activity and 24 h reduction in germination time relativeto untreated. The effect of two different pressure plasma treatments at constant power and exposure time were also investigated. The result showed that the low-pressure plasma treatment was a more effective way to increase the germination rate at a smaller plasma treatment time. Using scanning electron microscope (SEM), the surface structure of plasma-treated and untreated C. tinctorium L. semen has been characterised. The SEM observations of Carthamii pericarpium and Hilum showed a change in the surface structure after plasma treatment. The physical structure of Carthamii pericarpium after plasma treatment looks softer relative to untreated. The Hilum of untreated C. tinctorium L. semen showed a very nice structure and boundary layer whereas after plasma treatment the structure was modified.     

Control of bio-MEMS surface chemical properties in micro fluidic devices for biological applications

Surface chemistry of silicon/glass based bio-MEMS was controlled by depositing plasma polymerized acrylic acid (ppAc) films at two different electrode positions in a two-stage plasma reactor. AFM and XPS were used to characterize the surface roughness and surface chemistry of the films, respectively. The surface of bio-MEMS was highly functionalized with carboxylic/ester functionalities with a very good surface uniformity. The proportion of carbon atoms as C-OX, C(==O)OX functionalities was decreased and an increase in C==O functionalities was observed when the electrode position was increased from the mesh. These functionalized bio-MEMS devices have advantages in fabrication of reusable micro fluidic devices and the variation of fluid velocity by changing the surface properties may be used to develop a micro-mixing system to control the mixing ratio of different fluids for different biological and chemical applications.     

Use of different size grids to control the surface chemistry of plasma‐polymerized acrylic acid films in a hybrid discharge

The surface chemistry of plasma‐polymerized acrylic acid (ppAc) films were controlled in a two‐stage (primary and processing) hybrid radio frequency (RF) discharge by changing the grid wire spacing (d_s). Two regions were defined in terms of d_s with respect to Debye length (λ_d) in the primary chamber at the grid to control the electron temperature (T_e) and surface chemistry of the ppAc films deposited in the processing chamber. A higher T_e (>3 eV) in the processing plasma was possible for d_s > λ_d, whereas decreasing d_s relative to λ_d reduced T_e. X‐ray photoelectron spectroscopy was used to characterize the ppAc films deposited on a glass substrate. The ppAc films surface characterization showed the maximum proportion of carbon atoms as carboxylic/ester [C(?O)OX] functionalities in C1s at the surface of films for the grid with d_s ≈ λ_d. The proportion of carbon atoms as ? [C(?O)OX] and COX in C1s at the surface decreased when d_s decreased relative to λ_d. The proportion of carbon atoms as carbonyl (C?O) at the film surface showed very good stability for all of the d_s values explored in this study. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2219–2224, 2007     

Using fast atomic source and low-energy plasma ions for polymer surface modification

A systematic study was carried out to characterize the effects of argon atomic beam irradiation and low-energy argon ions in plasma for polystyrene (PS) surface modification. The PS samples were exposed to a 1.5 keV, argon atomic beam from a fast atomic source (FAS) at different exposure times. The low-energy (1.5 eV) argon plasma ions were achieved in a two-stage RF discharge and PS samples were exposed to plasma for different times and powers. The surface characterization of these atomic beam and plasma modified PS samples was carried out using X-ray photoelectron spectroscopy. For FAS, the results showed a rapid increase (from 0.01 to 0.18) in oxygen-to-carbon ratio (O/C) at the surface of PS with first 10 s exposure time while further increase in exposure time up to 500 s showed about 50% decrease in O/C. Therefore, first few seconds of atomic beam irradiation useful to increase the O/C at the PS surface whereas at higher irradiation time the surface etching may took places and it could have advantage in surface cleaning. A comparison of O/C with FAS and plasma ions showed FAS is more effective way to achieve oxygen incorporation at PS surface relatively to low-energy flux plasma ions.