Polymer Ablation

It is confirmed that the polymer matrix around ablated area was also affected strongly by laser ablation. The change of the matrix properties are brought about over a few tens of pin. This type of information is basically important and indispensable for practical applications such as excimer laser lithography. The time-resolved fluorescence spectroscopy is one of the powerful characterization methods for ablated polymer matrix. 

Process optimization of the thermal treatment of an ablation polymer material, based on phenolformaldehyde resins, was done by time and temperature, by the application of simplex optimization. 

D.L. Pugmire, E.A. Waddell, R. Haasch, J.J. Tarlov and L.E. Locascio, Surface characterization of laser-ablated polymers used for microfluidics. Anal. Chem., 74 (2002) 871-878. 

The presence of titanium dioxide in the alkyd resin films is concluded to play an important role in the photocatalytic decomposition of the latter species. A number of articles have appeared on the laser ablation user of polymers and the photodecomposition products.In controlled etching the intensity of the laser is extremely important for introducing reactive surface functional groups. Intense laser pulses whilst they cause ablation do not give the polymer radicals time enough to react with oxygen. Product distributions also vary enormously depending on the polymer structure. For example, with poly(methyl methacrylate) at 193 nm, 18% of the ablated polymer is monomer while at 248 nm less than 1% monomer is produced. 

The surface of the ablated polymer reveals a composition very similar to the starting material. 

These criteria resulted in the design of laser ablation polymers for 308 nm as irradiation wavelength, where it is possible to separate the absorption bands of the photochemically active chromophore from the aromatic groups in the polymer. The importance of this concept was discussed previously. Irradiation of the polymers with 248 nm caused carbonization of the polymer surface, while irradiation with 308 nm did not yield carbonization. These results prove that our concept of separating the absorption bands is valid, but... 

The surface characteristics of a microfluidic channel are very important in determining the flow in electrokinetically driven systems. In electrokinetically driven systems, the bulk flow is created by movement of the mobile diffuse layer near the channel wall/solution interface that is termed electroosmotic flow (EOF). The EOF is dependent on the surface of the microchannel walls. Roberts et al. demonstrated the generation of EOF on laser-ablated polymer substrates for the first time, using the parallel processing mode with a photomask and an ArF excimer laser at 193 nm [17]. A variety of polymer substrates such as polystyrene, polycarbonate, cellulose acetate, and poly(ethylene terephthalate) (PET) were ablated to fabricate microfluidic channels. The laser ablation process alters the surface chemistry of the machined regions and produced negatively charged. 

There are differences in the surface of the laser-ablated polymer depending on the mode of operation, static and dynamic laser ablation mode. Rossier et al. investigated differences in surface states of polymer PET as a result of these two modes of ablation [18], Their studies revealed that the static ablation mode produced a homogeneous and hydrophobic surface with poor wettability, whereas the dynamic ablation mode produced an inhomogeneous and hydrophilic surface with high wettability. These differences were attributed to the redeposition of fragments. 

Pugmire DL, Waddell EA, Haasch R, Tarlov MJ, Locascio LE (2002) Surface Characterization of Laser-Ablated Polymers Used for Microfluidics. Anal Chem 74(4) 871-878... 

---