A new technique manipulating soft polymer putty has been developed by Segei Sheiko and her fellow researchers at University of North Carolina at Chapel Hill. Their technique has allowed for the creation of morphing putty with a molecular controllable time clock to determine the rate of shapeshifting. Furthermore, they have found a way to use “building block” molecule formations to create designs that would allow complex shapes to transform at different rates. Their innovative work appears promising in the eyes of biomedical engineering, says fellow developer of changing materials Michael Kessler from Washington State University.
It is possible to create morphing materials and have them change to a specific shape but these necessitate the use of an external activator, such as change in temperatures, or specific changes in environment like pH levels. The application of this technology is extremely limited as there are situations in which the structures are isolated from external stimulation such as when inside the human body. Sheiko’s new molecular design would allow for the structures to change at a designed time by building it in into the material itself.
The polymer has a structure that is held together by bonds that are majority shape-shifting and usually snap “in a split second” according to Sheiko, but this putty had added molecules that are resistant, elastic, and permanent links maintaining the bonds and shaped of the structure together even after stretching it out. Subsequently, extending the time it takes for the structure to snap back into place allows for the timing of its desired change.
Difficulties arose when the material needed to have “pauses” or “dormant periods” or even accelerate the rate of change in the material. Unable to find a way to program in to the putty’s molecular structure these interruptions or accelerations in rate of change of the material, the team decided to add an extra water-soluble layer that would create the interval of time needed before activating change. By manipulating the thickness of that extra layer they could extend the time. Dropping the putty in water has some effect of the internal clock as well.