Laser photoablation

Rossieretal. [332] usedUV excimer laser photoablation to cut channels 50 microns deep by 100 microns wide in laminated PET. These channels were filled with PA, and rapid separation of proteins by isoelectric focusing was demonstrated. 

Rossier et al. [80] used UV excimer laser photoablation for changing the surface properties of the plastics and drilling. The authors discussed the method for patterning biomolecules on a polymer along with surface coverage of active antibodies and equilibration time. Besides, a method of designing NCE comprising an on-chip injector, column and electrochemical detector was also discussed. Furthermore, the potential of this disposable device was discussed and compared to classical systems. 

Mixing in a PMMA T-junction was achieved by chaotic advection in the channel with slanted grooves created by laser photoablation (see Figure 3.40) [193,257,470]. Mixing could also be achieved in a PDMS microchannel using square grooves in the channel bottom (see Figure 3.41) [471]. 

Schwarz, A., Rossier, J.S., Bianchi, F., Reymond, F., Ferrigno, R., Girault, H.H., Micro-TAS on polymer substrates micromachined by laser photoablation. Micro Total Analysis Systems 98, Proceedings jlTAS 98 Workshop, Banff, Canada, 13-16 Oct. 1998. Kluwer Academic Publishers, Dordrecht, the Netherlands, 1998, 241-244. 

Feldmann, D., Kutzner, J., Laukemper, J., MacRobbert, S., and Welge, K.H., "Mass Spectroscopic Studies of the Arf-Laser Photoablation of Polystyrene," Appt Phys. 

Estler R, NogarN. (1986) Mass spectroscopic identification of wavelength dependent UV laser photoablation fragments from polymethylmethacrylate. ApplPhys Lett 1175. 

Sarig-Nadir, O., Livnat, N., Zajdman, R., Shoham, S., SeUktar, D. Laser photoablation of guidance microchannels into hydrogels directs ceU growth in three dimensions. Biophys. J. 96, 4743-4752 (2009)... 

The irradiation of a polymer surface with the high intensity, pulsed, fer-UV radiation of the excimer laser causes spontaneous vaporization of the excited volume. This phenomenon was first described by Srinivasan (1) and called ablative photodecomposition. The attention of many researchers was drawn to the exceptional capabilities of photoablation (2). Etching is confined to the irradiated volume, which can be microscopic or even of submicron dimensions, on heat-sensitive substrates like polymers. In most experimental conditions, there is no macroscopic evidence of thermal damage, even when small volumes are excited with pulses of... 

The photoablation behaviour of a number of polymers has been described with the aid of the moving interface model. The kinetics of ablation is characterized by the rate constant k and a laser beam attenuation by the desorbing products is quantified by the screening coefficient 6. The polymer structure strongly influences the ablation parameters and some general trends are inferred. The deposition rates and yields of the ablation products can also be precisely measured with the quartz crystal microbalance. The yields usually depend on fluence, wavelength, polymer structure and background pressure. 

The photoablation process consists of the absorption of a short-wavelength laser pulse to break covalent bonds in polymer molecules and eject decomposed polymer fragments. Channels of various geometries and dimensions can be obtained using an appropriate mask. Many commercially available polymers can be photoablated, including polycarbonate, poly(methyl methacrylate) (PMMA), polystyrene, nitrocellulose, poly(ethylene terphtalate) (PET), and poly(tetrafluoroethylene) (Teflon). ... 

Microfabrication by means of laser radiation covers a wide range of different methods (24,25). On the one hand, these are processes where material is removed in an intense electromagnetic field by melting, evaporation, decomposition, photoablation, or a combination of these phenomena. On the other hand, generating processes exist where structures are built up from liquid resins, laminated layers, or powders using, e.g., photochemically induced crosslinking of organic compounds... 

Ablation using radiations of various wavelengths (IR, visible, UV, or x-ray) has been employed to fabricate plastic chips. For instance, photoablation using pulsed UV lasers (193 nm) has been used to fabricate plastic chips out of polyethylene terephthalate (PET, 100 pm thick) [189,190, 258,758] and polycarbonate (PC, 125 pm thick) [189,258]. Channels as narrow as 30 pm and as deep as 100 pm can be made [258,758]. The cross section of a photoablated PET channel plate laminated with another PET using a thin PE adhesive layer was shown in Figure 2.20 [191]. 

A XeCl excimer laser (308 nm) was used to photoablate biodegradable polymers (PDLA and PVA) into channels (10-50 pm deep) [196],... 

Photoablation (diode-pumped Nd YV04 laser, X = 532 nm) was used to create a master on the PMMA layer coated on a Si wafer (see Figure 2.20a). The PMMA layer was doped with rhodamine B to facilitate the absorption of the laser radiation. The width of the ablated features depends on the diameter and the position of the laser focal point. The best aspect ratios were obtained with the laser beam focused 3 1 pm into the PMMA film. The ablated PMMA-Si master was used to cast a PDMS layer (see Figure 2.19b). The cast PDMS layer appeared to have smoother surfaces than the PMMA master [367]. 

Hydrophilicity of polymeric channels can also be increased by photoablation. For instance, polymeric channels (37 pm deep) were photoablated through a copper foil mask. Relative to the original polymer, the photoablated surface is rougher and has increased hydrophilicity. The EOF increases in the following order PC < PS < cellulose acetate < PET [194]. The excimer laser ablation has... 

A large number of papers has appeared on the subject of excimer laser exposure of polymer films (16-21). Most of these have dealt with the phenomenon of photoablation. A few have observed intensity dependent photochemistry (22,23). The latter authors were concerned with the effect of exposure intensity on resist development characteristics. The utility of nonlinear photochemistry for image modification has not been explored except in our earlier communication, in which strongly nonlinear irreversible bleaching was observed for KrF laser irradiation of acridine/PMMA films with lOnsec pulses (5). 

Photoablation of Copolymers, Other workers have also investigated the phenomenon of polysilane self-development. Zeigler and co-workers (13) have studied the self-development of a number of polysilane homo- and copolymers and found that self-development eflSciencies increase with the size of substituents. They also suggested that the material removal process for alkyl-substituted poly silanes at low fluences (<50 mj/cm per pulse) is predominantly photochemical rather than photothermal. By using a 1 1 copolymer, poly(methyl-n-propylsilane-co-isopropylmethylsilane), images were generated by excimer laser exposure at 248 nm. 

The olefins represent the first stable products isolated from the photoablation of substituted polysilanes, and as such, any mechanistic hypothesis must include these species. The absence of literature precedents for photochemical silicon-carbon bond cleavage suggests the possibility of a thermal route. This suggestion is further strengthened by the observation that exposure of a number of polysilanes to IR radiation from a cw CO 2 laser results in gaseous mixtures with compositions (as determined by mass spectral analyses) that closely resemble those produced by irradiation at 308 nm. 

Direct photon effect on a substrate is photoablation of a solid surface. After the substrate absorbs strong laser light, the material at the irradiation site is spontaneously etched away to a depth of 1 This... 

During this study, we have found that laser intensity is one of the important factors that control laser surface chemistry. At a small laser intensity, molecules adsorbed on solid surfaces dissociate into atoms and radicals. Some of these atoms or radicals react with atoms of the solid substrates. At a large laser intensity, atoms are photoablated from the solid surfaces to react with the molecules adsorbed or in the gas phase. Hence, we describe in this paragraph a) the dynamical study of UV laser photodissociation of halogen or metal-containing molecules on solid surfaces, b) reactions of atoms generated in the photodissociation of an adsorbate with solid surfaces, and c) reactions of molecules in the gas phase with the photoelectrons or metal atoms generated on intense laser irradiation of solid surfaces. 

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