Laser microfabrication

Bowden M., Geschke O., Kutter J.P., Diamond D., C02 laser microfabrication of an integrated polymer microfluidic manifold for the determination of phosphorus, Lab On a Chip 2003 3 221-223. 

Haller K.L., Bumm L.A., Altkom R.I., Zeman E.J., Schatz G.C., Vanduyne R.P., Spatially resolved surface enhanced 2nd harmonic-generation - theoretical and experimental-evidence for electromagnetic enhancement in the near-Infrared on a laser microfabricated Pt surface, J. Chem. Phys. 1989 90 1237-1252. 

The field of laser lithography (also often called laser microfabrication) branched out from multiphoton excitation microscopy and has become established during the last decade. The principles of two-photon microscopy, which has enabled high-resolution 3D imaging [3,4] and optical memory [5], were gradually adapted for 3D laser hthography [6]. A relevant collection of seminal papers on the field can be found in [7]. 

Acknowledgements We are indebted to our colleagues, coauthors, and students for numerous discussions on various aspects of laser microfabrication. We acknowledge the discussions and insights of Profs. S. John and G. Ozin on the properties of spiral PhC and for Si-infiltration of SU-8 spiral structures. We also acknowledge the comments of Prof. V. Datsyuk on field enhancement effects. 

Misawa H, Juodkazis S (eds) (2006) Three-dimensional laser microfabrication fundamentals and applications. Wiley, UK... 

Juodkazis S, Misawa H, Vanagas E, Li M (2006) Thermal effects and breakdown in laser microfabrication. In Online Proc LAMP2006 4th int congress on laser advanced materials processing, Kyoto, 16-19 May, 2006. JLPS, Osaka, pp 06-60... 

Duncan AC, Weisbuch F, Rouais F, Lazare S, Baquey C. Laser microfabricated model surfaces for controlled cell growth. Biosens Bioelectron 2002 17 413-26. 

Two-photon three-dimensional (3D) micro- and nanofabrication using a femtosecond laser have been used to create various types of 3D micro- and submicrometer structures [70, 74, 260, 265, 574], A microscope with axial (z) and lateral (r) resolutions given by Eqs. (77) and (78) was used for laser microfabrication [574]. Wavelength of irradiation light (/.), refractive index of the material (/ ), and numerical aperture of the objective lens (NA) influence the resolution in axial and lateral directions. 

Femtosecond laser microfabrication of periodic structures using a microlens array. Appl. Phys. A, 80 (4), 683-685. 

Laser microfabrication technique is also commonly present in most of the microfluidic laboratories. This technique is growing very fast recently and is contributing toward... 

Figure 10.31 shows the picture of a laser micromachining center. In laser microfabrication, a highly directional light beam, that is, laser, is focused close to diffraction-limited spot size, which is incident on the matter to be machined. The availability of pulse laser at higher repetition rates adds to the capability of laser-based microfabrication. This technique avoids a lengthy and wasteful multistep approach based on lithography. 

Fig. 10 Two-photon direct writing laser microfabrication system. The Galvano mirror set is used for scanning the laser beam in the two horizontal dimensions, and along the longitudinal direction a PZT stage is used. The laser power was continuously adjusted by a neutral density (ND) filter. The polarization beam splitter (PBS) lets the laser beam pass but reflects the illumination light to the CCD monitor for in-situ monitoring of the fabrication process. OL objective lens...

Similar to the case of two-photon excitation, for multiphoton absorption the initiators would perform an operation of k y[n] with a much smaller coefficient k for w-photon absorption. The above two methods and knowledge acquired about the focal spot related to two or multiphoton excitation is essential for not only photopolymerization fabrication, but also important for understanding excitation behavior for various laser microfabrications. 

Fig. 42 Photocurable gelatin for application to femtosecond laser microfabrication, a Chemical structures of styrene-derived gelatin, b photogelation mechanism by formation of cross-linked gelatin networks via intermolecular crosslinking and intramolecular polymerization...

D microfabricated reactor devices are typically made by fabrication techniques other than stemming from microelectronics, e.g. by modern precision engineering techniques, laser ablation, wet-chemical steel etching or pEDM techniques. Besides having this origin only, these devices may also be of hybrid nature, containing parts made by the above-mentioned techniques and by microelectronic methods. Typical materials are metals, stainless steel, ceramics and polymers or, in the hybrid case, combinations of these materials. 

The microstructure is part of a bottom plate a top plate serves as a cover [21]. Direct-write laser lithography and wet-chemical etching were employed for microfabrication of the bottom plate. Holes were drilled in the top plate to give conduits for the inlet and outlet ports. The top and bottom plates were bonded thermally. 

Optical properties of the material are less critical for microchips hyphenated with MS than for devices with on-chip optical detection where low background absorption or fluorescence is mandatory. Thus, completely opaque polymers like glassy carbon or polyimide " can be used as microfabrication substrates. Furthermore, polymer microchips are of great interest because their potentially low manufacturing costs may allow them to be disposable. Methods used for the fabrication of plastic chips include laser ablation and molding methods. 

In terms of beam delivery, the DLW method is based on optical microscopy, confocal microscopy [4,6,13] and laser tweezers [14] (for reviews on laser tweezers see [ 15,16]). These techniques allow for a high spatial 3D resolution of a tightly focused laser beam with optical exposure of micrometric-sized volumes via linear and nonlinear absorption. In addition, mechanical and thermal forces can be exerted upon objects as small as 10 nm molecular dipolar alignment can be controlled by polarization of light in volumes of with submicrometric cross-sections. This circumstance widens the field of applications for laser nano- and microfabrication in liquid and solid materials [17-22]. 

It is noteworthy that nonlinearity of the absorption, required for 3D microfabrication can be provided via thermal mechanisms [53,54]. In the case of tightly focused laser pulses, linear absorption is most efficient at the focus, where local heating can create the conditions required for polymerization. Usually the absorption increases with temperature and thermal polymerization may become dominant at the focus. It is usually difficult to confirm the TPA mechanism from the direct transmission measurements due to the nar-... 

Juodkazis S, Matsuo S, MisawaH, MizeikisV, SunAMB, Tokuda Y, TakahashiM, Yoko T, Nishii J (2002) Application of femtosecond laser pulses for microfabrication of transparent media. Appl Surf Sci 197-198 705-709... 

Plastic materials have gained importance in microfabrication due to their ease of molding, inexpensiveness, and disposability. Some workers have used these substrates for fabrication of microchips. Pethig et al. [78] and Roberts et al. [79] used laser ablation as a direct method for creating microchannels in plastic chips without the need for fabrication. The methods used an UV excimer laser to bum the microchannels onto the polymer substrate, moving in a predefined,... 

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