Self-assembled polymer films for controlled agent-driven motion.

Reliable stimuli-responsive materials make up a vital part of molecular medicine and on-chip diagnostics. Here, we describe such a material which exhibits rapid, large-amplitude, reversible deformations and which is formed in a simple, one-material, one-step, self-assembly process. The material is a polymer network comprised of discrete molecular actuators which anisotropically expand in response to their driving stimuli. Tuning the relative orientation of the actuators with respect to one another creates expansion variations throughout a sample, and this is exploited to induce macroscopic motion. The deformation directions are pre-engineered by the molecular positioning, and extremely fast response times and high sensitivity are observed. We describe water- and pH-controlled motion, and we anticipate that the techniques are extendable to other biologically or industrially relevant agents.