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Spontaneous assembly and real-time growth of micrometre-scale tubular structures from polyoxometalate-based inorganic solids


We report the spontaneous and rapid growth of micrometre-scale tubes from crystals of a metal oxide-based inorganic solid when they are immersed in an aqueous solution containing a low concentration of an organic cation. A membrane immediately forms around the crystal, and this membrane then forms micrometre-scale tubes that grow with vast aspect ratios at controllable rates along the surface on which the crystal is placed. The tubes are composed of an amorphous mixture of polyoxometalate-based anions and organic cations. It is possible for liquid to flow through the tubes, and for the direction of growth and the overall tube diameter to be controlled. We demonstrate that tube growth is driven by osmotic pressure within the membrane sack around the crystal, which ruptures to release the pressure. These robust, self-growing, micrometre-scale tubes offer opportunities in many areas, including the growth of microfluidic devices and the self-assembly of metal oxide-based semipermeable membranes for diverse applications.

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Figure 1: The molecular building blocks used to form microtubes.
Figure 2: Spontaneous tube formation from crystals.
Figure 3: Micromanipulation is used to control tube growth and branching.
Figure 4: Different tube-fusion events upon collision.
Figure 5: Control of tube growth direction in a two-electrode system.
Figure 6: Injection of fluorescein isothiocyanate dye into a tube.


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The authors would like to thank the Leverhulme Trust (London), the Royal Society, the University of Glasgow, WestCHEM and the EPSRC for funding.

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Authors and Affiliations



L.C. conceived and designed the experiments, analysed the data, and prepared the manuscript, with help from C.S., C.R. and G.C. C.R. synthesized the clusters and the tubes, A.P. synthesized the cations, G.C., C.R., H.Y. and Y.S. performed the experiments with the tubes, and H.Y. fabricated the patterned structures. C.S. and D.M. performed the electron microscopy.

Corresponding author

Correspondence to Leroy Cronin.

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Ritchie, C., Cooper, G., Song, YF. et al. Spontaneous assembly and real-time growth of micrometre-scale tubular structures from polyoxometalate-based inorganic solids. Nature Chem 1, 47–52 (2009).

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