Microfabrication procedure

Microchips fabrication with integrated tips can result in improved spray repeatability and efficiency since alignment and dead volume are not a critical issue anymore. However, production of fine and robust nanospray emitters as an integral part of a microdevice is not trivial, and highly specialized microfabrication procedures are required. Microfluidic devices with integrated ESI tips have been produced for infusion experiments, but to date, no microchips with such a design was fabricated for CE separation prior to MS detection. 

FIGURE 2.20 SEM representation of the cross section of a PET microchannel made by photoablation. The trapezoidal form is typical for this type of microfabrication procedure. The lamination on the top is evidenced by the interface between the polymer layers. The channel dimensions are 30 pm wide in the bottom, 40 pm wide in the top, and 40 pm deep [191]. Reprinted with permission from Elsevier Science. 

Transmission electron microscopy (TEM) is probably the most powerful technique for obtaining structural information of supported nanoparticles [115-118], Complementary methods are STM, AFM, and SEM. Both the latter and TEM analysis provide more or less detailed size, shape, and morphology information, i.e., imaging in real space. TEM has the great additional advantage to provide information in Fourier transform space, i.e., diffraction information, which can be transformed to crystal structure information. From a practical point of view, considering the kinds of planar model catalysts discussed above, STM, AFM, and SEM are more easily applied for analysis than TEM, since the former three can be applied without additional sample preparation, once the model catalyst is made. In contrast, TEM usually requires one or more additional preparation steps. In this section, we concentrate on recent developments of microfabrication methods to prepare flat TEM membrane supports, or windows, by lithographic methods, which eliminate the requirement of postfabrication preparation of model catalysts for TEM analysis. For a more comprehensive treatment of other, more conventional, procedures to make flat TEM supports, and also similar microfabrication procedures as described here, we refer to previous reviews [118-120]. 

The microfabrication procedure for the TEM membrane windows is shown schematically in Fig. 4.22. A more detailed outline of the procedure is described in [124,125]. The windows are typically fabricated on 3-in. double side polished, n-type Si(lOO) wafers. In the first step, the wafers are cleaned with the two-step standard cleaning procedure used in the semiconductor industry. This procedure ensures the removal of all the organic particles by oxidation, metals by forming soluble complexes, and the native oxide with HF as shown schematically in step 1 of Fig. 4.22 (these steps are hazardous and... 

The glass chip used for the same-single-ceU analysis was fabricated by the standard microfabrication procedure, with the channel depth of 20 pm (Fig. 3) [21]. This microfluidic chip was applied for analysis of human wild-type (WT) T-ceU leukemic cell line CCRF-CEM (CEMAVT, dmg sensitive) and its multidrug-resistant vinblastine-selected subline (CEMA LBO.05) [5, 21]. 

The physical configuration and the microfabrication procedure of microsynthetic jet, microbaUoon, and microflap actuators are discussed in this section. 

At the center of the microfabrication procedure is the need to make a very accurate representation of the microelectrode (as the mask), for it is this original that will determine the quality of all subsequent devices. In addition, in order to ensure a faithful reproduction, careful... 

Figure 2.4 shows some types of refractive microlenses that can be fabricated utilizing the standard microfabrication procedures in materials convenient for the MWIR and LWIR ranges. Most of them are loosely based on the solutions for microlenses used in fiber optics to improve coupling between laser sources and fibers [98]. These immersion lenses were thus intended for the operation with coherent and monochromatic radiation, while most of the microlenses in the field of IR detector technology are intended for incoherent, mono- or polychromatic Lambertian sources and, of course, they operate in different atmospheric windows. 

Figure 10.8 The decomposition of microfabrication procedure to three primary steps, that is, addition, multiplication, and subtraction of thin sohd film...

The decomposition of microfabrication procedure to three primary steps, that... 

The material used for microfluidics should be appropriate for fabrication of such micrometer-scale features and should allow for integration of functional components. Early microfluidic systems were fabricated by photolithography and etching of silicon and glass [2], which have desirable surface characteristics but also some serious Hmitations. Polymers can replace these materials in microfluidic technologies, as they involve much simpler and less expensive microfabrication procedures [2-6]. Polyfdimethylsiloxane) (PDMS) seems to be one of the most suitable materials for microfluidic appHcations [ 1,7j. It exhibits a range of unique properties ... 

---