Three-dimensional profile stitching based on the fiducial markers for microfluidic devices

Profile acquisition of microfluidic devices is a challenging task due to the competing requirements of both large field of view (FOV) and high-resolution. One strategy for obtaining such measurement is linking or stitching high-resolution profiles, possibly from multiple instruments, into a large FOV profile. As opposed to current stitching techniques relying on precise control and measurement of the translation of the sample stage, our approach presented in this paper takes advantage of the overlapping of fiducial markers, to align and stitch the separately measured profiles of a device. This method allows three-dimensional profiles transformed in six degrees of freedom. so that the pitch, roll and yaw among measurements are compensated, and stitching can be processed in both in-plane and out-of plane directions. Measurements of microfluidic channels recorded by an atomic force microscope and a white-light interferometer are stitched with accuracies evaluated to be 0.086 mu m and 0.094 mu m, respectively. Stitching experiments for large-scale profile gets an accuracy of 0.047 mu m. Special form of stitching for profiles acquired by different tools, i.e. key parts of a device profile measured by a small FOV high-resolution instrument are stitched into a large FOV low-resolution profile by another instrument, is also carried out with an accuracy of 0.224 mu m. (C) 2008 Elsevier B.V. All rights reserved.