  Active materials with distinctive nonequilibrium properties have diverse
materials science applications. Active systems are common in living matter,
such as the filament network in the cell that is activated by molecular motors,
and in materials science as exemplified by hydrogels activated by chemical
reactions. Here we describe another class of active polymeric filament systems
where the filaments are activated by embedded chemically-powered nanomotors
that have catalytic and noncatalytic parts. Chemical reactions on the catalytic
surfaces produce forces that act on the polymeric filaments. By changing the
nonequilibrium conditions these forces can be made to change sign and thereby
compress or expand the filaments. The embedded motors provide both the source
of activity and the means to control the filament conformational structure. As
an example of control, we show that oscillatory variations of the chemical
constraints yield gel-like networks that oscillate between expanded or
compressed forms, much like those of hydrogels.
