Fabrication, microstructure bonding

Besides PMMA, compression molding was also used to fabricate microstructures on PC chips (1 mm thick). High temperature (188°C) and pressure (11 metric ton pressure applied by a hydraulic press) were used. Before bonding, the hydrophobic channel surface was treated with UV irradiation (220 nm) to increase surface charge, which would assist aqueous solution transport. The molded chip was thermally bonded to another PC wafer. During use, the bonded chip did not yield to a liquid pressure up to 150 psi (134°C, 4 metric ton, 10 min) [938],... 

Fabrication was done by photolithography and deep reactive ion etching (DRIB). The catalyst was inserted by sputtering. Such a prepared microstructure was sealed with a Pyrex cover. The bonded micro device was placed on a heating block containing four cartridge heaters. Five thermocouples monitored temperature on the back side. A stainless-steel clamp compressed the device with graphite sheets. 

Two microstructured layers of the 2x2 chip were fabricated by photolithography and wet etching in glass (Figure 4.11) [23,24]. These top and bottom layers and a third thinner layer containing holes as conduits were thermally bonded to yield the chip. The way of guiding the micro charmels, as described above, is referred to as two-level crossing. 

Because of their strong chemical bonds, bulk ceramics are most efficiently fabricated by means of densification of powders. The fabrication process involves two main stages (1) consolidation of the powder to form a porous, shaped article (the green body), also referred to as forming, and (2) heating of the shaped powder form to produce a dense article, referred to as firing or sintering. The final product commonly consists of a relatively dense polycrystal with some residual porosity (Fig. 1). The microstructure, which... 

It was found that the p-type compound was relatively dense. The density was increased with increasing the pressing temperature because of the porosity decrease. The decrease results from an improvement in the bonding between the powders. We could not fabricate successfully the compound at 440 U because of the local melting of the powders. The melt was identified as Te used as a dopant. Fig. 1 shows the optical microstructures along the longitudinal and transverse directions for the compound hot pressed at 420 °C. The dark areas shown in Fig. 1 correspond to the pores. The porosity present in the compound was decreased with the pressing temperature. 

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