Small diameter carbon nanopipettes

Abstract

Nanoscale multifunctional carbon probes facilitate cellular studies due to their smallsize, which makes it possible to interrogate organelles within living cells in aminimally invasive fashion. However, connecting nanotubes to macroscopic devices andconstructing an integrated system for the purpose of fluid and electrical signal transferis challenging, as is often the case with nanoscale components. We describe anon-catalytic chemical vapor deposition based method for batch fabrication of integratedmultifunctional carbon nanopipettes (CNPs) with tip diameters much smaller(10–30 nm) than previously reported (200 nm and above) and approaching thoseobserved for multiwalled carbon nanotubes. This eliminates the need for complicatedattachment/assembly of nanotubes into nanofluidic devices. Variable tip geometries andstructures were obtained by controlled deposition of carbon inside and outsidequartz pipettes. We have shown that the capillary length and gas flow rate have amarked effect on the carbon deposition. This gives us a flexible protocol, useful forgrowing carbon layers of different thicknesses at selective locations on a glasspipette to yield a large variety of cellular probes in bulk quantities. The CNPspossess an open channel for fluid transfer with the carbon deposited inside at875 °C behaving like an amorphous semiconductor. Vacuum annealing of the CNP tips at temperatures up to2000 °C yields graphitic carbon structures with an increase in conductivity of two orders of magnitude.Penetration of the integrated carbon nanoprobes into cells was shown to produce minimalCa2+ signals, fastrecovery of basal Ca2+ levels and no adverse activation of the cellular metabolism during interrogation times aslong as 0.5–1 h.