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Download as PDFNanoporous Elements in MEMS with a Focus on Microfluidic Bioparticle Separation
We integrated ultra-porous (99% porous) elements (nanoporous forests of vertically aligned carbon nanotubes (VACNTs)) in MEMS, showing their use in microfluidic applications for bioparticle isolation and health diagnostics. Distinct from works where the effects of fluids on VACNT elements resulted in either structural deformation or catastrophic forest collapse [1] , our approach enables creation of high aspect ratio (~ 1-mm) nanoporous elements and preserves their shape under flow-through conditions. Figure 1 shows a device, consisting of a patterned and (wet) functionalized VACNT forest integrated into a PDMS microfluidic channel.
Compared to state-of-the-art designs that exploit solid materials (e.g., silicon, PDMS) for the structural features, our nanoporous elements enable flow around and through the VACNT elements, enhancing physical interaction between the particles in the flow and the functional elements. Multiple device layouts demonstrated a ~7X increase in specific bioparticle capture when transitioning to VACNT porous designs [1] . The large surface-to-volume ratio of nanoporous materials yields a significant increase in the functional surface area (~250-500X for the layouts analyzed in our works [2] [3] ), with permeability comparable to that of macro-scale porous materials [4] , thus further promoting bioparticle capture.
Specific isolation of bioparticles ranging over 4 orders of magnitude in size (from cells to viruses) was experimentally demonstrated (Figure 1), including the ability to perform simultaneous multiphysics, multiscale isolation on a single chip [4] . Particles smaller than the average distance between single nanotubes in the VACNT elements (~80 nm) can penetrate the elements and can be isolated using chemical affinity; simultaneously, particles larger than 80 nm cannot enter the nanoporous elements and can be isolated on the elements’ outer surfaces using both mechanical filtration and biomolecular recognition. The nanoporous elements are versatile and could provide access to underexplored sub-micron particles (e.g., proteins, exosomes).
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- Figure 1: Example of a nanoengineered biodevice for bioparticle isolation [2] .
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- Figure 2: Simultaneous isolation of particles ranging three orders of magnitude in size on a single chip using an array of functionalized VACNT pillars [4] .
- D. N. Futaba, K. Hata, T. Yamada, T. Hiraoka, Y. Hayamizu, Y. Kakudate, O. Tanaike, H. Hatori, M. Yumura, and S. Iijima. “Shape-engineerable and highly densely packed single-walled carbon nanotubes and their application as super-capacitor electrodes,” Nature Materials, vol. 5, pp. 987-994, 2006. [↩] [↩]
- G. D. Chen, F. Fachin, M. Fernandez-Suarez, B. L. Wardle, and M. Toner, “Nanoporous elements in microfluidics for multiscale manipulation of bioparticles,” Small, vol. 7, pp. 1061-1067, 2011. [↩] [↩]
- F. Fachin, G. D. Chen, M. Toner, B. L. Wardle, “Integration of vertically-aligned carbon nanotube forests in microfluidic devices for multiscale isolation of bioparticles,” Proc. of IEEE Sensors, 47-51, 2010. [↩]
- F. Fachin and G.D. Chen, M. Toner, and B. L Wardle, “Integration of bulk nanoporous elements in microfluidic devices with application to biomedical diagnostics,” Journal of Microelectromechanical Systems, vol. 20, no. 6, pp. 1428-1438, 2011. [↩] [↩] [↩]