  The propulsion and acceleration of nanoparticles with light have both
fundamental and applied significance across many disciplines. Needle-free
injection of biomedical nano cargoes into living tissues is among the examples.
Here we explore a new physical mechanism of laser-induced particle
acceleration, based on abnormal optothermal expansion of mesoporous vaterite
cargoes. Vaterite nanoparticles, a metastable form of calcium carbonate, were
placed on a substrate, underneath a target phantom, and accelerated towards it
with the aid of a short femtosecond laser pulse. Light absorption followed by
picosecond-scale thermal expansion was shown to elevate the particles center of
mass thus causing acceleration. It was shown that a 2um size vaterite particle,
being illuminated with 0.5 W average power 100 fsec IR laser, is capable to
overcome van der Waals attraction and acquire 15m/sec velocity. The
demonstrated optothermal laser-driven needle-free injection into a phantom
layer promotes the further development of light-responsive nanocapsules, which
can be equipped with additional optical and biomedical functions for delivery,
monitoring, and controllable biomedical dosage to name a few.
