Micro-electromagnetic rotary motors realized by deep x-ray lithography and electroplating.

摘要

The inability in the micromechanics field to achieve high performance batch-fabricated microactuators for micro-electro-mechanical systems (MEMS) has largely been a result of limited existing planar microfabrication capability. In particular, a method has been lacking to produce devices with significant thicknesses from a large material selection including magnetic materials while maintaining component precision. Such attributes are found in LIGA or deep x-ray lithography (DXRL) and electroplating techniques which originated in work at the Kernforschungszentrum (Nuclear Research Center) in Karlsruhe, Germany. These techniques can produce prismatic metal structures with several hundred micron thickness and lateral run-out less than {dollar}rm0.1mu m{dollar} of structure thickness.; The application of DXRL and electroplating methods to the construction of a planar integrated rotational magnetic micromotor is described. Several extensions of the basic DXRL and electroplating process have ensued. A micro-assembly approach incorporating sacrificial layer processing has enabled the achievement of sub-micron intercomponent tolerances at several hundred micron structural heights. Magnetic material with relative permeability over 2000 is incorporated by using the electroplated alloy 78/22 Ni/Fe or 78 Permalloy. An integrated shaft encoder is implemented through the co-fabrication of silicon microelectronics. Polymethylmethacrylate (PMMA) photoresist of nearly arbitrary thickness to over 1cm is achieved using a new application process.; A three-phase variable reluctance stepping micromotor design is primarily investigated with rotor radii between {dollar}rm75mu m{dollar} and {dollar}rm 500mu m{dollar} thickness up to {dollar}rm 200mu m.{dollar} A vertical rotor suspension which lifts the rotor as much as {dollar}rm 50mu m{dollar} above the substrate is incorporated to substantially reduce frictional forces. A hysteresis micromotor is also described which makes use of a composite PMMA/metal component process.; Real-time rotor position response data is used to measure micromotor performance. A maximum output torque of 300nN-m has been achieved with a {dollar}rm500mu m{dollar} radius rotor and a maximum rotational speed of 150,000rpm in air has been obtained with a {dollar}rm75mu m{dollar} radius rotor. Micromotors have been tested to {dollar}3(10)sp9{dollar} rotational cycles after which no sign of wear is evident. Results for a planar external gear-train coupling scheme are presented which enables dynamometry measurements.