  In this work we present some results of the treatment of polydimethylsiloxane
(PDMS) surfaces using pulsed dielectric barrier discharge plasmas. The results
of plasma treatment using different gases and mixtures, argon, argon plus water
vapor, helium, helium plus water vapor, nitrogen and nitrogen plus water vapor,
were compared testing the adhesion between two PDMS samples for each kind of
plasma. We also studied the water contact angle in function of plasma process
time of PDMS surfaces with each kind of plasma treatment. The plasma was
characterized by optical emission spectroscopy (OES) to identify the emitting
species and determine the plasma temperatures. The plasma temperature for each
process was estimated comparing the spectrum obtained by OES with the spectrum
generated by SpecAir simulation code. Measurements of power delivered to the
plasmas were also performed. As the results, all the process using different
gases show good adhesion efficacy between PDMS samples when long exposure time
(larger than 150 seconds) is applied. However, when only a few discharges are
applied to PDMS samples the helium plasma process presented best results.
Atomic Force Microscopy (AFM) analysis of PDMS samples treated with helium
plasma showed reduction in the surface roughness, which increase the surface
contact area and improves the adhesion.
