Magnetic shape-shifting

By flecking magnetic nanoparticles throughout a thermoplastic polymer composite, researchers in Germany have created a polymer that changes shape in response to a magnetic field (Proc. Natl. Acad. Sci. USA, published online Feb. 28, dx.doi.org/10.1073/pnas.0600079103). The material, created by Andreas Lendlein of the Institute of Polymer Research in Teltow and coworkers, is a new twist on shape-memory polymers. Shape-memory materials can be deformed into a temporary shape and then snapped back into their original predefined shape when exposed to an external stimulus. Heat is typically used to stimulate the material's shape-shifting, but for certain applications, such as medical implants, applying heat directly to these polymers is impractical. The magnetic particles Lendlein incorporated into his group's shape-memory polymer trigger shape changes via inductive heating when placed in an alternating magnetic field (shown). Lendlein says the material could be used to make smart catheters and drug delivery systems.