  Plasmonic colour printing based on engineered metasurfaces has revolutionized
colour display science due to its unprecedented subwavelength resolution and
high-density optical data storage. However, advanced plasmonic displays with
novel functionalities including dynamic multicolour printing, animations, and
highly secure encryption have remained in their infancy. Here we demonstrate a
dynamic plasmonic colour display technique that enables all the aforementioned
functionalities using catalytic magnesium metasurfaces. Controlled
hydrogenation and dehydrogenation of the constituent magnesium nanoparticles,
which serve as dynamic pixels, allow for plasmonic colour printing, tuning,
erasing and restoration of colour. Different dynamic pixels feature distinct
colour transformation kinetics, enabling plasmonic animations. Through smart
material processing, information encoded on selected pixels, which are
indiscernible to both optical and scanning electron microscopies, can only be
read out using hydrogen as a decoding key, suggesting a new generation of
information encryption and anti-counterfeiting applications.
