(751b) Coherence Resonance in a Single Walled Carbon Nanotube Ion Channel

Authors: 
Choi, W., Massachusetts Institute of Technology
Lee, C. Y., Ulsan National Institute of Science and Technology (UNIST)
Han, J., Massachusetts Institute of Technology
Strano, M. S., Massachusetts Institute of Technology


Biological signaling networks are able to utilize coherent and oscillatory signals from intrinsically noisy and stochastic components for ultrasensitive discrimination using stochastic resonance, a concept not yet demonstrated in man-made analogs. We show that the longest, highest aspect ratio, and smallest diameter synthetic nanopore examined to date, a 500 μm single walled carbon nanotube (SWNT), approximately 1.5 nm in diameter, demonstrates oscillations in electro-osmotic current at specific ranges of electric field, that are the signatures of coherence resonance, a form of stochastic resonance, yielding self-generated rhythmic and frequency locked signals. SWNT were grown on a SiO2 wafer and connected between two bonded, aqueous reservoirs at their plasma-etched and open ends. Stochastic pore blocking is observed when individual cations (Na+, Li+, K+, 1 M) partition into the nanotube during electro-osmosis, partially obstructing an otherwise stable proton current. We report the highest recorded proton conductivity experimentally observed (5×102 S/cm), suggesting an ordered water phase in the SWNT interior. The observed oscillations in the current occur due to a coupling between stochastic pore blocking and a diffusion limitation that develops at the pore mouth during proton transport. This is the first example of resonant transport in a synthetic nanopore, and illustrates how simple ionic transport can generate coherent waveforms within an inherently noisy environment, and points to new types of nano-reactors, sensors, and nanofluidic channels based on this platform.