Substrate-based fabrication

As an example of Si technology, Figure 1 illustrates a packaged 1-megabit dynamic-random-access-memory (DRAM) chip on a 150-mm-diameter Si substrate containing fabricated chips. Each of the chips will be cut from the wafer, tested, and packaged like the chip shown on top of the wafer. The chip is based on a l- xm minimum feature size and contains 2,178,784 active devices. It can store 1,048,516 bits of information, which corresponds to approximately 100 typewritten pages. 

Semiconductor fabrication techniques permit the feature size of Si-based devices to reach into the deep submicron regime [i]. Additionally, Si can be anodized electrochemically or chemically (e.g., in an HF-containing electrolyte) to produce a sponge-like porous layer of silicon, with pore dimensions that range from several microns in width to only a few nanometers [ii]. These properties of Si make it a useful substrate for fabricating sensor platforms, photonic devices and fuel cell electrodes [iii]. 

In scouring, the presence of a chelating agent prevents formation of heavy metal soaps and other compounds which prevent good cleaning. Thus a cleaner base fabric affords a better substrate for dyeing. 

It has also been shown that a self-assembled monolayer (SAM) with proper functional groups can significantly improve the adhesion of CP thin film on a substrate. Based on this concept, Jung and Lee have demonstrated the fabrication of CP nanostmctures via a lift-off process. In their study, 16-mercaptohexadecanolc acid and 3-aminopropyltriethoxy silane SAM were used on Au and Si02/Si surfaces to promote the adhesion of PPY and PEDOT PSS, respectively. This allowed nanostmctures of these CP materials to be fabricated using standard e-beam lithography followed by a lift-off process [14]. 

When the particles act as the filtration substrate, the base fabric then acts as a support. Depth filtration occurs when the particles are held within the fibres of the fabric filter, through electrostatic and van der Waals forces. These forces result in particles that are smaller than the aperture of the filter being captured within the fibres. 

Base fabric n. In coated fabrics, the underlying substrate. 

Coating and laminating are very exciting technologies with a myriad of possibilities [15]. The aim of coating or laminating a textile substrate with a polymer layer is to significantly influence its external characteristics and physical properties. Textiles coated with, or laminated, bonded with a continuous polymer layer acquire new properties that cannot be achieved by the base fabric alone. 

The mesh itself is usually based on a plain weave pattern. Some important properties of the screen mesh are the size and density of the strands (usually quoted in terms of lines per inch), the tension, the orientation, and the material, hi addition, the choice of mesh material must ensure that the printed deposit is uniform. The mesh material must be precisely woven and have uniform mesh apertures. The fabric should also be flexible enough to enable good contact all over the substrate. The fabric needs to be resilient so that the mesh returns to its original position after the printing stroke. The squeegee itself is in contact with the fabric for most of the printing stroke, so the finish of the fabric must be slippery and smooth so that the resistance to the squeegee is minimal. The mesh material must also be chemically stable and very resistant to attack... 

Figure 5.33a shows the electrowetting-based tunable liquid lens on a flexible substrate. The fabrication of such a lens takes advantage of the transfer technique discussed in Chapter 3. The lens structure was first formed as an island housing the lens on a thin polymer substrate. Both the housing island and the substrate could be made of PDMS. The whole structure could then be wrapped conformally onto a curvilinear surface. 

Yoon et al. [48] proposed a liquid junction free polymer membrane-based reference electrode system for blood analysis under flowing conditions. They used silicmi wafers as well as ceramic substrate to fabricate ion selective sensors with an integrated reference electrode. The silver chloride layer was coated with a membrane based on aromatic polyurethane (PU 40 membrane) with equimolar amounts of both cathodic and anodic lipophilic additives (TDMACl and KTpCIPB) to reduce the electrical resistance (see Chaps. 12 and 13). The ceramic-based sensors were fabricated by screen-printing methods. Both reference electrodes showed a rather stable potential in various electrolyte solutions with different pH values and different concentrations of clinically relevant ions, providing that the ionic strength of the solution is over 0.01 M. The integrated ISE cartridge based on the ceramic chip could be used continuously for a week. 

The patterning capabilities of SECCM have been further exploited in the creation of 3D structures by McKelvey et al. In contrast to previous meniscus-based fabrication techniques, which tended to use single-channel devices to make contact with a substrate at a limited number of points, SECCM allows the fabrication of structures on conducting substrates, across... 

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