  Metasurfaces enable manipulation of light propagation at an unprecedented
level, benefitting from a number of merits unavailable to conventional optical
elements, such as ultracompactness, precise phase and polarization control at
deep subwavelength scale, and multifunctionalities. Recent progress in this
field has witnessed a plethora of functional metasurfaces, ranging from lenses
and vortex beam generation to holography. However, research endeavors have been
mainly devoted to static devices, exploiting only a glimpse of opportunities
that metasurfaces can offer. We demonstrate a dynamic metasurface platform,
which allows independent manipulation of addressable subwavelength pixels at
visible frequencies through controlled chemical reactions. In particular, we
create dynamic metasurface holograms for advanced optical information
processing and encryption. Plasmonic nanorods tailored to exhibit hierarchical
reaction kinetics upon hydrogenation/dehydrogenation constitute addressable
pixels in multiplexed metasurfaces. The helicity of light, hydrogen, oxygen,
and reaction duration serve as multiple keys to encrypt the metasurfaces. One
single metasurface can be deciphered into manifold messages with customized
keys, featuring a compact data storage scheme as well as a high level of
information security. Our work suggests a novel route to protect and transmit
classified data, where highly restricted access of information is imposed.
