Integration of Bulk Nanoporous Elements in Microfluidic Devices With Application to Biomedical Diagnostics

We demonstrate integration of ultraporous (99% porous) elements composed of nanoporous forests of vertically aligned carbon nanotubes (VA-CNTs, or VACNTs) in microelectromechanical systems (MEMS), illustrating their use in fluidic applications for biomedical diagnostics. Our method enables definition of high-aspect-ratio (~10
⁴
, heights ~100 μm, and pore spacings ~10 nm) nanoporous elements and preserves the VACNT elements' shapes even under flowthrough conditions. The fluid permeability of the VACNT elements is measured experimentally and shown to be comparable to that of much larger micro- and macroscopic porous materials. Permeability tailoring of VACNT elements through manipulation of both material and CNT growth process parameters is also experimentally demonstrated. Distinct from solid designs (e.g., Si and polydimethylsiloxane), our approach enables fluid flow both around and through the nanoporous microfluidic elements, hence enhancing isolation efficiency by increased physical interaction between the particles in the flow and the functional elements. Simultaneous multiphysics (chemical and mechanical) and multiscale (several orders of magnitude in size) isolation of bioparticles using microfluidic devices with nanoporous elements is demonstrated as well.