Laser-induced microfabrication

As already stated earlier, the direct laser technique applied to sol-gel films has the advantage of being maskless, allowing rapid and simple processing compared with masked-based photolithographic techniques [74]. In addition, the direct laser writing can be tuned by adjusting independently the focus conditions, the 

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The /i-TAS offers some excellent possibilities and is in a state of rapid development. However, several challenges need to be overcome for their successful real-world implementation. For example, detection limits are low due to the small sample size, and the principal detection method so far is laser-induced fluorescence, which offers high sensitivity and low detection limits. Other problems include interfacing microfabricated devices to conventional macro-size instruments and fluid handling. 

Figure 11 Fast mutation detection via heteroduplex analysis on a microfabricated electrophoretic chip. The heterozygous mutants were specified in the figure. The separation buffer was 2.5% HEC containing 10% glycerol in 1xTBE (pH = 8.6) for (a-d) and 4.5% HEC containing 10% glycerol and 15% urea in 1xTBE (pH =8.6) for (e-f). The microchannel on the chip was coated with PVP (Mr 1,000,000) and detection mediated by laser-induced fluorescence (em/ex 520 nm/488 nm). The PCR products were injected into the channel for 100 s at 333 V/cm (effective microchannel length of 5.5 cm), and the separation voltage was 573 V/cm. (Reprinted with permission from Ref. 69.)...

The first microfabricated capillary array electrophoresis (p,CAE) device appeared in 1997 [3] featuring 12 separation channels interrogated by a scanning laser-induced fluorescence (LIF) detector. 

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... 

Zhou et al. [177] use a random copolymer of tetrahydropyranyl methacrylate (THPMA) and methyl methacrylate (MMA) polymer doped with BSB-S2 as the PAG for microfabrication. At the laser focal spot, the THPMA groups were converted to carboxylic acid groups due to photogenerated acid-induced ester cleavage reactions, and were therefore rendered soluble in aqueous base developer. Figure 45 shows the 3D microstructure produced by this method. By two-photon fluorescence imaging, it was found that the buried channels are open and a continuous connection was made between the two cavities. 

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