THE LIGA PROCESS FOR FABRICATION OF 3-DIMENSIONAL MICROSCALE STRUCTURES

Three-dimensional microscale structures can be fabricated with the Lig a process, which uses deep etch X-ray lithography, electroforming and plastic moulding. The basic process has been extended in order to incr ease the number of possible applications. Some of the extensions inclu de: movable microscale structures produced using a sacrificial layer t echnique; structures with different shapes in the third dimension obta ined by patterning plastic substrates as well as by a moulding techniq ue and by X-ray lithography; and micropumps developed by combining Lig a with a membrane technology. The improved process together with the g reat variety of materials (plastics, metals, alloys, ceramics) that ca n be used opens up many potential applications of Liga in microsystem technologies. A few prototype applications are briefly described: micr oturbines with diameters of the order of 100 mu m, rotating at 150000 rev min(-1) for 10(8) revolutions; microsensors which can measure acce leration with high accuracy, e.g. of crashing cars; micromotors with d iameters of 0.25 mm driven by electrical forces; and micropumps which can deliver very small amounts of liquids and even gases. In the futur e all these microcomponents will be integrated with microelectronic de vices to create 'intelligent' microsystems which are expected to chang e our life in the way that the microelectronic revolution did in the p ast.