Microfabrication of Three-Dimensional

Bulk micromachining Microfabrication of three-dimensional features such as membranes, cavities, and so on by anisotropic dry or wet etching into the bulk of substrate materials like silicon, quartz, or others. 

S. Johansson, J. A. Schweitz, H. Westberg and M Boman, Microfabrication of three-dimensional boron structures by laser chemical processing, J. Appl. Phys. 72 [12], 5956-5973 (1993). 

The modern methods of three dimensional microfabrication have lead to the development of extremely miniaturized chemical and biotechnological systems. These so called microreactors represent novel approaches in respect of production flexibility and chemical reactions not yet applied in chemical processing. This has stimulated world-wide research in this field so that the technical feasibility of such devices has been demonstrated in the laboratory scale. 

An additional class of nonlinear optical effects is that of multi-photon absorption processes. Using these process, one can create excited states (and, therefore, their associated physical and chemical properties) with a high degree of three-dimensional (3D) spatial confinement, at depth in absorbing media. There are potential applications of multi-photon absorbing materials in 3D fluorescence imaging, photodynamic therapy, nonlinear optical transmission and 3D microfabrication. 

D microfabrication 3D micromachining Microfabrica-tion of three-dimensional microstructures Three-dimensional patterning Fabrication of 3D microfluidic channels... 

Three-dimensional electrode arrays have been fabricated using two very different micromachining methods. One approach, named carbon MEMS or C-MEMS, is based on the pyrolysis of photoresists. The use of photoresist as the precursor material is a key consideration, since photolithography can be used to pattern these materials into appropriate structures. The second approach involves the micromachining of silicon molds that are then filled with electrode material. Construction of both anode and cathode electrode arrays has been demonstrated using these microfabrication methods. 

Design and application of high-sensitivity two-photon initiators for three-dimensional microfabrication. Photochem J Photobiol A Chem 158(2-3) 163-170... 

Maruo S, Ikuta K (2000) Three-dimensional microfabrication by use of single-photon-absorbed polymerization. Appl Phys Lett 76 2656-2658... 

Future work will focus on real three-dimensional electrodes that may slowly penetrate the superficial layer of the retina. We hope to improve the spatial selectivity of a stimulator structure and to lower the energy consumption during stimulation, when the microelectrode is in close proximity to the somata of the ganglion cells. A possible design of this structure is shown in Fig. 27. It demonstrates the design potentials that microfabrication of polymer based microstructure offer. 

Several techniques for miniaturization of simple chemical and medical analysis systems are described. Miniaturization of total analysis systems realizes a small sample volume, a fast response and reduction of reagents. These features are useful in chemical and medical analysis. During the last decade many micro flow control devices, as well as the micro chemical sensors fabricated by three dimensional microfabrication technologies based on photofabrication, termed micromachining, have been developed. Miniaturized total analysis systems (pTAS) have been studied and some prototypes developed. In microfabricated systems, microfluidics , which represent the behavior of fluids in small sized channels, are considered and are very important in the design of micro elements used in pTAS. In this chapter microfluidics applied flow devices, micro flow control devices of active and passive microvalves, mechanical and non-mechanical micropumps and micro flow sensors fabricated by micromachining are reviewed. 

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. 

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