Photolithographic techniques applications

This type of coil was prepared from copper cladded printed circuit board material by applying photolithographic techniques. The p.c. board material is available with difierent copper thicknesses and with either a stiff or a flexible carrier. The flexible material offers the opportunity to adapt the planar coil to a curved three dimensional test object. In our turbine blade application this is a major advantage. The thickness of the copper layer was chosen to be 17 pm The period of the coil was 100 pm The coils were patterned by wet etching, A major advantage of this approach is the parallel processing with narrow tolerances, resulting in many identical Eddy current probes. An example of such a probe is shown in fig. 10. 

Many of the variations developed to make pressure sensors and accelerometers for a wide variety of applications have been reviewed (5). These sensors can be made in very laige batches using photolithographic techniques that keep unit manufacturing costs low and ensure part-to-part uniformity. A pressure differential across these thin diaphragms causes mechanical deformation that can be monitored in several ways piezoresistors implanted on the diaphragm are one way changes in electrical capacitance are another. 

The next step for this technology is the development of dry microactuators that can work outside of a liquid. On the macroscale, it has been demonstrated that conjugated polymers can actuate in ionic liquids [132,134], These room temperature liquid salts can be incorporated into gels [135], which wfll allow the fabrication of patterned electrolyte containing solid layers using photolithographic techniques. This development will expand the range of possible applications. 

Most applications of microchip CE have used laser-induced fluorescence detection because of the ease of focusing directly onto the small channel on the chip. Electrochemical detection is ideally suited for miniaturization to the microchip format. The photolithographic techniques that are already used to make the microchips can also be used to fabricate miCTon-sized detection electrodes reproducibly and inexpensively without a loss in sensitivity. If the power supply and potentiostat are also miniaturized, it is possible to envision a complete miniaturized total analysis system [4,53]. 

As an example of a patterning technique in polymers, we will discuss in more detail photoembossing, a photolithographic technique for the generation of polymeric relief structures. In this particular case, the relief structure develops as a result of a material flux induced by a local polymerization. The material flux deforms the surface of the film, which is permanently fixed by the photoinitiated crosslinking process without the interference of a solvent development step [9, 27, 28]. Therefore this principle is attractive in an economic sense for applications that require the structuring of large surfaces. 

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