Carbon nanotube pipettes can be used to release tiny amounts of copper iodide in a controlled fashion using electrical pulses
Carbon nanotubes have great potential as miniature pipettes to deliver minute amounts of drugs, but it has so far been difficult to control the amount of chemical released. Now Pedro Costa and Dmitri Goldberg at the National Institute for Materials Science in Tsukuba and co-workers1 have found a way of using nanotubes to store and release controlled amounts of copper iodide on the scale of attograms (10-18 grams).
The researchers treated multiwalled nanotubes so that their ends were opened, then filled them with copper iodide. The copper iodide collects in distinct crystals inside the nanotube, which can be released one-by-one when a pulse of electrical current is applied. This release process is different to previous experiments, in which crystals have broken up or melted and the filling is continuously expelled from the nanotube.
Furthermore, the researchers found that the conductance of the nanotube increases as copper iodide is released because the edges of the copper iodide grains slow down charge carriers. This means that the amount of copper iodide left in the nanotube can be monitored either by measuring the nanotube resistance or by watching the nanotube under a transmission electron microscope.
References
Costa, P. M. F. J. et al. Stepwise current-driven release of attogram quantities of copper iodide encapsulated in carbon nanotubes. Nano Lett. 10.1021/nl8012506 (2008).
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Reid, T. One drop at a time. Nature Nanotech (2008). https://doi.org/10.1038/nnano.2008.282
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DOI: https://doi.org/10.1038/nnano.2008.282
