Dielectrophoretic Trapping of Single Bacteria at Carbon Nanofiber Nanoelectrode Arrays

Abstract

We present an ac dielectrophoretic (DEP) technique for single-cell trapping using embedded carbon nanofiber (CNF) nanoelectrode arrays (NEAs). NEAs fabricated by inlaying vertically aligned carbon nanofibers in SiO2 matrix are applied as "points-and-lid" DEP devices in aqueous solution. The miniaturization of the electrode size provides a highly focused electrical field with the gradient enhanced by orders of magnitude. This generates extremely large positive DEP forces near the electrode surface and traps small bioparticles against strong hydrodynamic forces. This technology promises new capabilities to perform novel cell biology experiments at the nanoscale. We anticipate that the bottom-up approach of such nano-DEP devices allows the integration of millions of nanolectrodes deterministically in lab-on-a-chip devices and will be generally useful for manipulating submicron particles.

Manipulation of bacteriophages with dielectrophoresis on carbon nanofiber nanoelectrode arrays

“…The generation of such patterns requires a relatively high concentration of polarizable particles and so is seen only when the particle flux is sufficiently high. Even though similar "pearlchain-like" patterns were observed by Suehiro et al in DEP trapping of E. coli cells between interdigitated microelectrodes [21], our previous DEP studies showed that only isolated E. coli cells were captured at the NE sites [15,16]. The larger size and higher internal conductivity of bacteria may have screened the high electric field at the NE tip and reduced the electrical interaction with additional cells.…”

“…Comparing the above virus capture results to the previous reports on the DEP capture of E. coli cells with similar NEA devices [15,16], four novel observations were made: (1) the optimum AC frequency was found to be ~10 kHz for virus as compared to 100 kHz to 1 MHz for E. coli. (2) The DEP capture of virus particles was observed even at ~8.9×10 4 pfu·ml −1 , more than 4 orders of magnitude lower than the concentration (~1×10 9 cfu·ml −1 ) used in previous E. coli studies.…”

“…As shown by the FEM simulation in our previous study [15], the magnitude of E 2 is highly focused at the nanoelectrode tip with an elongated distribution in vertical direction like a spear. The magnitude of E 2 dropped quickly from ~1.2×10 14 V 2 m −2 at the center of a disk-shaped nanoelectrode to ~1.8×10 7 V 2 m −2 at ~600 nm above [15]. E 2 dropped by the same magnitude in lateral direction only ~50 nm from the outside the edge of the nanoelectrode [15].…”

“…1a). The embedded VACNF were fabricated as described previously [15][16][17][18]. Briefly, a 4" silicon (100) wafer (Si-Tech, Topsfield, MA) was diced into small chips of 1 cm × 2 cm.…”

“…Here we demonstrate the use of a NEA as 'point' electrodes vs. a macroscopic indium tin oxide (ITO) electrode used as the 'lid' electrode in a "points-andlid" configuration [7] to create a highly non-uniform electric field for DEP capture of virus particles. From our previous work, ∇E 2 within a distance of 3 μm above the embedded VACNF nanoelectrode (NE) tip can be as high as ~1.2×10 18 V 2 m −3 [15], about 200 times higher than the microscale "points-and-lid" devices. The size of the CNFs (~50-200 nm in dia.)…”