We report a chemically driven membrane shape instability that triggers the ejection of a tubule growing exponentially toward a chemical source. The instability is initiated by a dilation of the exposed monolayer, which is coupled to the membrane spontaneous curvature and slowed down by intermonolayer friction. Our experiments are performed by local delivery of a basic $p\mathrm{H}$ solution to a giant vesicle. Quantitative fits of the data give an intermonolayer friction coefficient $b\approx 2\times {10}^9\mathrm{J}\mathrm{s}/{\mathrm{m}}^4$. The exponential growth of the tubule may be explained by a Marangoni stress yielding a pulling force proportional to its length.

• Received 19 June 2008

DOI:https://doi.org/10.1103/PhysRevLett.102.018102