  The quest for wave channeling and manipulation has driven a strong research
effort on topological and architected materials, capable of propagating
localized electromagnetical or mechanical signals. With reference to an elastic
structural grid, which elements can sustain both axial and flexural
deformations, it is shown that material interfaces can be created with
structural properties tuned by prestress states to achieve total reflection,
negative refraction, and strongly localized signal channeling. The achievement
of a flat lens and topologically localized modes is demonstrated and tunability
of the system allows these properties to hold for a broad range of wavelengths.
An ingredient to obtain these effects is the use, suggested here and never
attempted before, of concentrated pulsating moments. The important aspect of
the proposed method is that states of prestress can be easily removed or
changed to tune with continuity the propagational characteristics of the
medium, so that a new use of vibration channeling and manipulation is envisaged
for elastic materials.
