The Liga Process for Fabrication of Three-Dimensional Microscale Structures

Abstract

Three-dimensional microscale structures can be fabricated with the Liga process, which uses deep etch X-ray lithography, electroforming and plastic moulding. The basic process has been extended in order to increase the number of possible applications. Some of the extensions include: movable microscale structures produced using a sacrificial layer technique; structures with different shapes in the third dimension obtained by patterning plastic substrates as well as by a moulding technique and by X-ray lithography; and micropumps developed by combining Liga with a membrane technology. The improved process together with the great variety of materials (plastics, metals, alloys, ceramics) that can be used opens up many potential applications of Liga in microsystem technologies. A few prototype applications are briefly described: microturbines with diameters of the order of 100 μm, rotating at 150 000 rev min^–1 for 10⁸ revolutions; microsensors which can measure acceleration with high accuracy, e.g. of crashing cars; micromotors with diameters of 0·25 mm driven by electrical forces; and micropumps which can deliver very small amounts of liquids and even gases. In the future all these microcomponents will be integrated with microelectronic devices to create ‘intelligent’ microsystems which are expected to change our life in the way that the microelectronic revolution did in the past.