Study for Integrating a Carbon Nanotube Filter onto a Microfluidic Chip

Abstract

We address the fabrication of a cost-effective and pore-size-controllable nanofilter using carbon nanotubes (CNTs) for a microdialysis chip. CNTs are actively studied because they have extraordinary mechanical, electrical, and structural properties. Numerous studies on microfluidic chips have enabled miniaturization of biochemical analysis processes. However, sample pretreatment such as sample purification are still performed off chips due to difficulties in the miniaturization of the sample pretreatment [1]. Dialysis is one of most frequently used sample pretreatment methods in conventional biochemical analysis. A CNT nanofilter can help perform dialysis at a micro-scale. In the current studies, a membrane type of a CNT filter is fabricated and located in a microfluidic chip, and is used as a dialysis membrane in a continuous flow system. Fabrication steps of a CNT nanofilter is as follows. Individual CNTs are entangled each other by amide bonding that is catalyzed by 1-Ethyl-3- (3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) [2]. The chemically treated CNTs are shaped to form a nanofilter using a PDMS film-mold and vacuum filtering. The vacuum filtering helps the CNT nanofilter homogenous. Then, the CNT nanofilter is sandwiched between a PDMS substrate and a cover and is bonded together to make a microdialysis chip. Both substrate and cover have a microchannel to perform a continuous-flow microdialysis. While a sample liquid flows through a microchannel, smaller molecules in the flow than the pores of the nanofilter are diffused into a perfusion channel across the nanofilter [3]. The pore size of a CNT nanofilter is controlled by varying the CNT density of a CNT solution and the length of CNTs. Details on the fabrication of the CNT nanofilter will be presented.