Monolithical Integration of Polymer based Microfluidic Structures on Application Specific Integrated Circuits Steffen Chemnitz a , Heiko Sch¨ afer a , Stephanie Schumacher a , Volodymyr Koziy a , Alexander Fischer a , Alfred J. Meixner b , Dietmar Ehrhardt a and Markus B¨ohm a a University of Siegen, Institute for Microsystem Technologies (IMT), H¨olderlinstrasse 3, D-57068 Siegen, Germany b University of Siegen, Institute of Physical Chemistry (PC I), Adolf-Reichwein-Strasse 2, D-57068 Siegen, Germany ABSTRACT In this paper, a concept for a monolithically integrated chemical lab on microchip is presented. It contains an ASIC (Application Specific Integrated Circuit), an interface to the polymer based microfluidic layer and a Pyrex glass cap. The top metal layer of the ASIC is etched off and replaced by a double layer metallization, more suitable to microfluidic and electrophoresis systems. The metallization consists of an approximately 50 nm gold layer and a 10 nm chromium layer, acting as adhesion promoter. A necessary prerequisite is a planarized ASIC topography. SU-8 is used to serve as microfluidic structure because of its excellent aspect ratio. This polymer layer contains reservoirs, channels, mixers and electrokinetic micro pumps. The typical channel cross section is 10 μm · 10 μm. First experimental results on a microfluidic pump, consisting of pairs of interdigitated electrodes on the bottom of the channel and without any moving parts show a flow of up to 50 μm per second for low AC-voltages in the range of 5 V for aqueous fluids. The microfluidic system is irreversibly sealed with a 150 μm thick Pyrex glass plate bonded to the SU-8-layer, supported by oxygen plasma. Due to capillary forces and surfaces properties of the walls the system is self-priming. The technologies for the fabrication of the microfluidic system and the preparation of the interface between the lab layer and the ASIC are presented. Keywords: ASIC, polymer, micro pump, microfluidics 1. INTRODUCTION The miniaturization of chemical labs results in numerous advantages, since the quantities of reagents can be reduced dramatically and chemical processes can be accelerated and highly parallelized. On the other hand, a growing number of microsystem technology applications, in particular in the field of microfluidics with its applications in life science, need novel fabrication methods for the control of the microfluidic system, allowing an easier fluid handling and data acquisition. This approach includes a vertical integration of an ASIC and a microfluidic system on only one chip. The microfluidic system is deposited in a CMOS-compatible post-process. According to Fig. 1, the Application specific Lab on Microchip (ALM) consists of four modules on top of each other. The ASIC acts simultaneously as substrate and contains custom specific circuitry for the control of the microfluidic system, e.g. for liquid transportation, process compartments and on-chip analysis tools. In the lab layer the chemical processes take place. It consists of a polymer in which channels and compartments were brought in by lithography, e.g. micropumps, mixers, arrays and detectors. On top of the polymer layer a Pyrex glass plate is placed to seal the microfluidic system. It also acts as a protective layer against environmental influences. The interface acts as contact between the ASIC and the lab layer. Further author information: (Send correspondence to) Heiko Sch¨afer: E-mail: heiko.schaefer@uni-siegen.de, Telephone: +49 271 740 4255 Smart Sensors, Actuators, and MEMS, Jung-Chih Chiao, Vijay K. Varadan, Carles Cané, Editors, Proceedings of SPIE Vol. 5116 (2003) © 2003 SPIE · 0277-786X/03/$15.00 782