A modular software system to assist engineers in designing microsystems is presented. The different modules support both the system and the component design and are linked with each other by a workflow management system. In particular, this paper presents the co-operation of the modules RUMTOPF, SUZANA and l-TOAST. They assist the designer in the definition and validation of process sequences, the simulation of wet chemical etching of silicon and the tolerance management. The usage and usefulness of the presented software system is illustrated by an example showing the design of an acceleration sensor.

Due to its cost effectiveness and reliability, wetchemical etching of silicon is still one of the key technologies for producing bulk-silicon microstructures. In this paper we present an approach for the design of advanced mask sets for anisotropic, wet-chemical etching of silicon. The optimization method of genetic algorithms is used to derive suitable masks for cases where geometrically calculated compensation structures fail. The underlying etch simulation is described as well as the optimization algorithm itself. Design tasks of current research projects are used as examples to illustrate the advantage of using the presented tool.

The electrophoretic mobilities of ribosomal ribonucleic acids (RNA) from cultured mammalian (HeLa, Vero, MDBK), avian (chick embryo), and bacterial ( Escherichia coli ) cells, and RNA species extracted from selected viruses (Sindbis, polio, tobacco mosaic, Sendai) were compared, employing a simple, inexpensive technique for slicing low-concentration polyacrylamide gels. The procedure provides for rapid fractionation of gels used for characterization of RNA, incorporating extrusion and serial sectioning of frozen gels. Among 28 S ribosomal RNA species, Vero and MDBK were indistinguishable, whereas HeLA RNA had a slightly lower mobility (higher apparent molecular weight) and chick RNA had a higher mobility (lower apparent molecular weight). The 18 S ribosomal RNA species of the three mammalian sources were indistinguishable, but chick 18 S RNA had a slightly lower apparent molecular weight. The inverse relation between mobility and log-molecular weight among the ribosomal and viral RNA species, though not highly precise, demonstrates the applicability of the technique to the study of molecular weights of viral RNA species.