For Shape-Memory Materials, Multiple Memories are Better than One

A new "smart materials" process developed by researchers in the Centre for Advanced Materials Joining based in the department of mechanical and mechatronics engineering at the University of Waterloo (Ontario, Canada) promises to remember a range of shapes, not just one. Known as multiple memory material technology, the process promises to revolutionize the manufacture of diverse products, including a range of medical devices such as stents and hearing aids, according to the scientists.

Traditional memory materials remember one shape at one temperature and a second shape at a different temperature. Until now such materials have been limited to changing shape at one temperature only. In contrast, the Waterloo technology can remember multiple memories, each with a different shape. It is hoped that the breakthrough technology will provide engineers with more freedom and creativity by enabling greater functionality to be incorporated into medical devices than is currently possible.

"This ground-breaking technology makes smart materials even smarter," remarks Ibraheem Khan, a research engineer and graduate student working with Norman Zhou, a professor of mechanical and mechatronics engineering at Waterloo. "We have developed a technology that embeds several memories in a monolithic smart material. In essence, a single material can be programmed to remember more shapes, making it smarter than previous technologies."

The patent-pending technology, which is available for licensing, allows virtually any memory material to be quickly and easily embedded with additional local memories. The transition-zone area can be as small as a few microns in width with multiple zones, each having a discrete transition temperature. As the processed shape-memory material is subjected to changing temperatures, each treated zone changes shape at its respective transition temperature. The transition zones created side by side allow for a unique and smooth shape change in response to changing temperatures.

Several prototypes have been developed to demonstrate this technology. One mimics a transformer robot. The robot's limbs transform with increasing temperature, whereas in conventional shape-memory technology, this transformation is limited to only one transformation temperature. A video demonstrating the miniature robot can be seen below.