Electrochemical microsystem technologies: from fundamental research to technical systems J.W. Schultze*, V. Tsakova 1 AGEF e.V.-Institut an der Heinrich-Heine-Universita Èt Du Èsseldorf, D-40225 Du Èsseldorf, Germany Received 9 September 1998; received in revised form 25 November 1998 Abstract The interdisciplinary ®eld of electrochemical microsystem technologies (EMST) has a large impact on electrochemistry, electrochemical engineering, microengineering, material science, chemical analysis and its applications in biology and medicine. EMST include electrochemical reactions applied in microsystem technologies (MST) as well as MST applied in electrochemistry. Fundamental research refers to the scaling-down of reactions taking place in the mm range. Control of electrochemical microreactions, their advantages and applications are discussed. The technical requirement of mass production presumes the scaling-up of the microreaction to a multifold macroscopic process. This is demonstrated for electrochemical processes, e.g. the LIGA process, as well as for MST for electrochemistry, e.g. the Foturan 1 technology. The ®nal industrial process requires the realization of multistep processes which is illustrated with the phosphating process and the printed circuit board manufacturing as examples. Electrochemical microsystems are presented and classi®ed by functionality and complexity. # 1999 Elsevier Science Ltd. All rights reserved. 1. Introduction During the last 30 years, electrochemical research became increasingly concerned with microscopic pro- blems. With the progress of micromechanics and the improved sensitivity of electrical equipment, measure- ments on miniaturized electrodes became possible. Simultaneously, progress in mathematics and simu- lation techniques allowed an improved modelling of microscopic systems. The ®rst calculations on micro- electrode reactions by Fleischmann [1] represent a typi- cal example. At ®rst, kinetic problems were solved and rates of diusion and migration were calculated. Later on, microscopic problems of the electrode surface and its modi®cations became of interest for corrosion and chemical analysis. The papers presented at the Faraday Discussion on ``The solid/liquid interface at high resol- ution'' [2] illustrate this type of research which allows solving of the special problems of materials science, corrosion and reaction kinetics. Simultaneously, elec- trochemical analysis was pushed ahead in biology and medicine. Due to the special requirements of measure- ments at biological membranes, ultramicroelectrodes with a high selectivity for various ions were developed. Thus, microelectrochemical techniques are now widely applied in biology and medicine. The achievements of Neher [3] and Sakmann [4] obtained by the patch clamp technique are a typical example for successful application in biological research. Finally, electroche- Electrochimica Acta 44 (1999) 3605±3627 0013-4686/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0013-4686(99)00065-1 * Corresponding author. Tel.: +49-21-1811-4750; fax: +49- 211-81-12803. E-mail address: joachimw.schultze@rz.uni-duesseldorf.de (J.W. Schultze) 1 On leave from the Institute of Physical Chemistry, Bulgarian Academy of Sciences, 1113 So®a, Bulgaria.