INSTITUTE OF PHYSICS PUBLISHING JOURNAL OF MICROMECHANICS AND MICROENGINEERING J. Micromech. Microeng. 16 (2006) 113–121 doi:10.1088/0960-1317/16/1/016 A novel fabrication method of flexible and monolithic 3D microfluidic structures using lamination of SU-8 films Patrick Abgrall 1 , Christine Lattes 2 , V´ eronique Con´ ed´ era 1 , Xavier Dollat 1 , St´ ephane Colin 2 and Anne Marie Gu´ e 1 1 LAAS-CNRS, 7 avenue du Colonel Roche, 31077 Toulouse Cedex 4, France 2 LGMT-INSAT,135 avenue de Rangueil, 31077 Toulouse Cedex 4, France E-mail: pabgrall@laas.fr Received 15 May 2005, in final form 20 October 2005 Published 13 December 2005 Online at stacks.iop.org/JMM/16/113 Abstract The fabrication of three-dimensional (3D) microfluidic networks entirely made of SU-8 with integrated electrodes is reported. The described technology allows the fabrication of uncrosslinked SU-8 dry film on a polyester (PET) sheet and its subsequent lamination to form closed microstructures. Unlike other reported methods, transferred layers are patterned following the bonding step allowing a more accurate and simple alignment between levels than techniques using already patterned layers. Dry release of the complete polymer microstructure was demonstrated. Flexible microfluidic chips were obtained. This technique uses simple tools and no wafer bonder is used but lamination techniques which are more collective processes. Limitations in the method for layers thicker than 50 µm have been observed and are discussed. Hydraulic flow experiments have been performed to study the deformation of the cover layer which could influence adjacent flow in a three-dimensional configuration. Important deformations have been observed for layers 10 µm thick and an average pressure greater than 100 kPa. No deformations have been noted for layers with thicknesses greater than 35 µm and for average pressures up to 200 kPa. No failures occurred within the range of the experimental set-up, i.e. up to 300 kPa. 1. Introduction Since the early works of Terry et al in the 1970s and particularly the introduction of the concept of micro total analysis systems (µTAS) by Manz in the 1990s [1, 2], there is a growing interest in coupling microfluidic structures (e.g. microchannels, microchambers) with conventional microsystems to form what is nowadays called a lab-on-a-chip (LOC). An important characteristic of these microfluidic chips compared to conventional microsystems is the large size necessary for many analytical functions such as chromatography and capillary electrophoresis where the integration of several centimetres long microchannels is required. Though monolithic approaches have driven the works in the 1990s with silicon and glass micromachining, it is obvious that these processes are not well adapted to microfluidic applications for many purposes. The high voltage often required in LOC excludes silicon. Glass processing is difficult and not cost effective. Polymer microfabrication techniques including casting, hot embossing, liquid injection, thermoforming, lamination and low-temperature bonding represent more suitable ways to fabricate such large microfluidic parts at low cost [3, 4]. So hybrid microsystems mixing polymer microfluidic devices and silicon electronic components are now investigated especially for high value added LOC. Another major concern is the control of surface properties since surface effects become increasingly dominant as size is diminished. Therefore, it is often necessary to fabricate 0960-1317/06/010113+09$30.00 © 2006 IOP Publishing Ltd Printed in the UK 113