  Since the historical experiments of Crookes, the direct manipulation of
matter by light has been both a challenge and a source of scientific debate.
Here we show that laser illumination allows to displace a vial of nanoparticle
solution over centimetre-scale distances. Cantilever-based force measurements
show that the movement is due to millisecond long force spikes, which are
synchronised with a sound emission. We observe that the nanoparticles undergo
negative thermophoresis, while ultrafast imaging reveals that the force spikes
are followed by the explosive growth of a bubble in the solution. We propose a
mechanism accounting for the propulsion based on a thermophoretic instability
of the nanoparticle cloud, analogous to the Jeans instability that occurs in
gravitational systems. Our experiments demonstrate a new type of laser
propulsion, and a remarkably violent actuation of soft matter, reminiscent of
the strategy used by certain plants to propel their spores.
