ABSTRACT
A fabrication process for monolithic integration of vertically aligned carbon nanotubes in electrically insulated microfluidic channels is presented. A 150 nm thick amorphous silicon layer could be used both for anodic bonding of a glass lid to hermetically seal the microfluidic glass channels and for de-charging of the wafer during plasma enhanced chemical vapor deposition of the carbon nanotubes. The possibility of operating the device with electroosmotic flow was shown by performing standard electrophoretic separations of 50 microM fluorescein and 50 microM 5-carboxyfluorescein in a 25 mm long column containing vertical aligned carbon nanotubes. This is the first demonstration of electroosmotic pumping and electrokinetic separations in microfluidic channels with a monolithically integrated carbon nanotube forest.
Subject(s)
Electrochemistry/instrumentation , Microelectrodes , Microfluidic Analytical Techniques/instrumentation , Nanotechnology/instrumentation , Nanotubes, Carbon/chemistry , Crystallization/methods , Electric Conductivity , Equipment Design , Equipment Failure Analysis , Nanotechnology/methods , Nanotubes, Carbon/ultrastructure , Particle Size , Systems IntegrationABSTRACT
Using a combination of top-down lithographic techniques, isolated, individual and oriented multi-wall carbon nanotubes (MWNTs) were grown on nickel or iron nanoscaled dots. In the first step of the process, micron-sized catalytic metallic dots (either iron or nickel) were prepared using UV lithography. MWNTs were then synthesized from these catalysts using a direct current plasma-assistance and hot-filament-enhanced chemical vapor deposition (CVD) reactor. Samples were characterized by means of scanning electron microscopy. It turns out that the splitting up of the micron-sized dot is favored in the iron case and that the surface diffusion of the metal is enhanced using ammonia in the gaseous mixture during the CVD process. The results are discussed giving arguments for the understanding of the MWNT growth mechanism. In a second step, a focused ion beam (FIB) procedure is carried out in order to reduce the initial dot size down to submicronic scale and subsequently to grow one single MWNT per dot. It is found that nickel is most appropriate to control the size of the dot. Dots of size 200 nm +/- 40 nm are then required to grow individual MWNTs.
