Topography, Crystallinity and Wettability of Photoablated PET Surfaces

Abstract

Surface topography, crystallinity, and wettability of photoablated poly(ethylene terephthalate) (PET) resulting from various ablation conditions have been characterized by atomic force microscopy (AFM), microconfocal Raman spectroscopy, and wettability measurements. Two ablation modes have been considered here: (i) static ablation, where the samples are immobilized in front of the pulsed laser beam and (ii) dynamic ablation, where the samples are moved in order to write three-dimensional structures in the polymer. Laser fluence, repetition rate, and speed of the substrate motion during the ablation process have been varied. The laser fluence has been observed to strongly affect the resulting surface roughness, which increased to a maximum value at fluences between 70 and 600 mJ‚cm -2 . For all fluences in the range of 1000-3000 mJ‚cm -2 , the roughness was found to be similar. No remarkable effects could be attributed to the pulse frequency of the 23 ns laser pulses. Raman spectroscopy studies demonstrated that the polymer surface exhibits a high degree of crystallinity when ablated in the static mode. Raman imaging of the surface indicated that these conditions also led to a more homogeneous surface state than when the polymer is ablated in the dynamic mode. Experiments measuring channel filling velocities by capillary action showed that the surfaces of structures fabricated in static photoablation mode were much more hydrophobic than those fabricated under dynamic photoablation.

Polymer microchips bonded by O2-plasma activation

“…It is remarkable that after water washing of the surface the O/C ratio decreases to 0.63, suggesting that some species such as low-molecular- weight redeposited and oxidized debris may have been removed from the surface. This observation is similar to the dynamic laser ablation of PET or polystyrene reported in different previous reports [24][25][26]. Due to the complex convolution in XPS spectra, it is difficult to determine, which functional groups have been created on the PET surface.…”

“…The standard bonding technique developed in our laboratory for more than five years [4] in order to seal polymer sheets is based on the lamination of an oxidized film of PE by a soft lamination technique [25]. Though the mechanical stability is satisfactory, Taylor dispersion and solvent compatibility may become serious problems for high-performance separation devices or for coupling to mass spectrometers.…”

Facile Preparation of a Patterned, Aminated Polymer Surface by UV-Light-Induced Surface Aminolysis

“…On the other hand, the autofluorescence from the virgin PET substrate has been proven and examined by Rossier and co-workers. [53,54] In our work, we used l-confocal Raman spectroscopy to elucidate the origin of the background intensity. As shown in Figure 8, the background intensity just outside the circle (spectrum b) was only slightly higher than that of the virgin PET surface (spectrum c).…”

New advances in microchip fabrication for electrochromatography

“…Channel sealing is accomplished by a lowcost film lamination technique with a lamination temperature for polyethylene terephthalate (PET)/PE at 1257C for 3 s that could allow premodification of the surface, which is not the case for glass chip bonding .5007C. The chemical properties of UV laser photoablated channels are described in [64].…”