Physicists Create Shapeshifting Single Molecule, Reacting to Stimuli

Researchers in Munich, Germany created a synthetic polymer molecule that can react to external stimuli by changing its shape, which could be useful for several applications in nanotechnology, like nano-scale switches and molecular machines.

Physicists at the Ludwig-Maximilians-Universität (LMU) have now for the first time created a chemical reaction that makes this process visible, using a single polymer molecule.

Dr. Michael Nash and his colleagues placed a self-generated synthesized polymer on a gold surface using an atomic force microscope (AFM). One polymer end adhered to the surface and the other end to the tip of the AFM.

For stimulation, the scientists increased the salt concentration of the surrounding medium, which caused the molecule to collapse gradually.

"In a highly concentrated salt solution, the polymer compound dehydrates and shrinks," says Nash. "Back in a weak salt solution, the molecule unfolds again.

"We have observed both processes in our study for the first time for a single polymer molecule."

The new method could provide an important element for nanoswitches of the future and could also be used in biosensors, drugs, chromatography procedures, and other applications, the researchers suggest.

Dr. Michael Nash is with the Prof. Hermann Gaub group, a member of The Cluster of Excellence Nanosystems Initiative Munich (NIM).

Paper: Michael A. Nash, and Hermann E. Gaub, Single-Molecule Adhesion of a Stimuli-Responsive Oligo(ethylene glycol) Copolymer to Gold, ACS Nano, 2012, DOI: 10.1021/nn303963m