Felix Schmitz

Design and realization of a penny-shaped micromotor

For many applications in rapid growing markets of microproducts, e.g. miniaturized hard disk drives in personal computers, mobile optical scanners, or for the market of consumer electronics, a novel, penny-shaped micromotor was developed at IMM. Designed to provide an output torque of more than 100 (mu) Nm, the permanent magnet motor shows a diameter of 12.8 mm and a height of 1.4mm. Besides the maximum torque and the ultra-flat shape, one further essential design parameter was a construction that allows an easy assembly and is suitable for mass-production. An important contribution to mass production philosophy is the intensive use of microfabrication technologies especially for both, the production of the permanent magnet rings by micro molding and micro compressing techniques and the micro coils by the way of photolithographic batch processes.

Tools and methods for automated assembly of miniaturized gear systems

The assembly of gear systems with the size of a pin head is almost beyond the bound of human tactile skills. The magic formula for series fabrication of this hybrid micro systems is the automation of the assembly process. As a contribution, this paper presents and discusses three different assembly methods comprising specifically developed tools for different types of planetary gears with outer diameters of 1.9 mm. Because of the huge importance for the complete micro assembly process, particular attention will be dedicated to the feeding and magazining of the micro gear components. Starting with metallic gear wheels as bulk good, an extremely miniaturized gear system of the Wolfram type has been automatically assembled by employing the strategy of tolerance compensation movement. As a key component, a modular tong gripper with specifically adapted gripping jaws produced by LIGA technology has been used. Further detailed investigations were spend on handling and assembly of micro injection moulded gear wheels made of POM for a three state planetary gear system. One strategy, following the idea of in situ observation, focuses on the intensive use of electronic pattern recognition. Alternatively, an unusual method based on a novel plastic wafer magazine will be discussed in detail. Hereby the exact position and orientation of injection moulded micro components will be presented from the manufacturing process up to the final micro assembly procedure. By simplifying the moulding of the micro gears as well as their handling, storing and assembly, this method has the potential to revolutionize the series fabrication of products with dimensions in the microscopic range in general.

Electromagnetic driving units for complex microrobotic systems

Electromagnetic actuators play an important role in macroscopic robotic systems. In combination with motion transformers, like reducing gear units, angular gears or spindle-screw drives, electromagnetic motors in large product lines ensure the rotational or linear motion of robot driving units and grippers while electromagnets drive valves or part conveyors. In this paper micro actuators and miniaturized motion transformers are introduced which allow a similar development in microrobotics. An electromagnetic motor and a planetary gear box, both with a diameter of 1.9 mm, are already commercially available from the cooperation partner of IMM, the company Dr. Fritz Faulhaber GmbH in Schonaich, Germany. In addition, a motor with a diameter of 2.4 mm is in development. The motors successfully drive an angular gear and a belt drive. A linear stage with a motion range of 7 mm and an overall size as small as 5 X 3.5 X 24 mm3 has been realized involving the motor, a stationary spur gear with zero backlash and a spindle-screw drive. By the use of these commercially available elements complex microrobots can be built up cost-efficiently and rapidly. Furthermore, a batch process has been developed to produce the coils of micro actuator arrays using lithographic techniques with SU-8 resin. In applying these components, the modular construction of complex microrobotic systems becomes feasible.

Assembly of optical fibers for the connection of polymer-based waveguide

This paper describes the realization of polymer-based optical structures and the assembly and packaging strategy to connect optical fiber ribbons to the waveguides. For that a low cost fabrication process using the SU-8TM thick photo-resist is presented. This process consists in the deposition of two photo-structurized resist layers filled up with epoxy glue realising the core waveguide. For the assembly, a new modular vacuum gripper was realised and installed on an automatic pick and place assembly robot to mount precisely and efficiently the optical fibers in the optical structures. First results have shown acceptable optical propagation loss for the complete test structure.

Miniaturized objective lens for a photoelectron emission microscope

Photoemission electron microscopy (PEEM) has turned out to be one of the most promising methods for surface analysis in the recent years. It is a full field imaging technique based on the emission of secondary electrons by far ultraviolet light or X-rays. The emission intensity of secondary electrons is critically dependent upon the acceptance angle of the incident radiation. However, the size of the microscope restricts this angle substantially. Miniaturizing the objective lens of the microscope reduces the restriction of the acceptance angle and improves the performance of the PEEM considerably. We report on the fabrication of a miniaturized objective lens containing the extraction electrode, the electron column, the contrast aperture and the electron optical correction system for a PEEM. The extraction electrode as well as the electron column have been manufactured using precision milling techniques and electron discharge micromachining. For the fabrication of the correction system (stigmator / bending unit), a process combining aligned photolithography into a thick SU-8 resist and electroforming has been used. All electrodes were made in gold with a height of 150 (mu) m. After attaching a FOTURAN substrate to the electrode and etching under the electrodes, free standing apertures in an octupole and quadruple arrangement were obtained. The outer diameter of the electrodes is 5 mm and the inner diameter is 1 mm, respectively. Each electrode is connect individually to the external power supply which controls their operation. The overall size of the miniaturized objective lens is 23 mm, which has reduced the size of the lens by one order of magnitude when compared to commercially available instruments.