Fabrication of combined-scale nano- and microfluidic polymer systems using a multilevel dry etching, electroplating and molding process

Microfabricated single-cell capture and DNA stretching devices have been produced by
injection molding. The fabrication scheme employed deep reactive ion etching in a silicon
substrate, electroplating in nickel and molding in cyclic olefin polymer. This work proposes
technical solutions to fabrication challenges associated with chip sealing and demolding of
polymer high-volume replication methods. UV-assisted thermal bonding was found to ensure a
strong seal of the microstructures in the molded part without altering the geometry of the
channels. In the DNA stretching device, a low aspect ratio nanoslit (1/200) connecting two
larger micro-channels was used to stretch a 168.5 kbp DNA molecule, while in the other
device single-HeLa cells were captured against a micro-aperture connecting two larger
microfluidic channels. Different dry etching processes have been investigated for the master
origination of the cell-capture device. The combination of a modified Bosch process and an
isotropic polysilicon etch was found to ensure the ease of demolding by resulting in slightly
positively tapered sidewalls with negligible undercut at the mask interface.