Researchers have developed a new kind of plastic that can take on three different shapes by adding heat. The new class of materials could one day play a transformative role in such industries as healthcare and beyond.
Researchers at MIT and the Helmholtz Association of German Research Centers have invented a class of materials so remarkable for their agility in changing shape as they react to heat, they might be described as acrobatic plastics.
The new materials, known as "triple-shape materials," can assume three different shapes, each shape depending on how much heat is applied.
This landmark achievement comes from the laboratories of chemical engineer Robert Langer of MIT and polymer chemist Andreas Lendlein of the Helmholtz Institute in Teltow, Germany.
“Triple-shape materials can switch from shape A, then to shape B, and on to shape C,” said Robert Langer, a professor of chemical and bioengineering at MIT, and one of the plastic’s developers.
Polymer chemist Andreas Lendlein of the Helmholtz Institute in Teltow, Germany, also worked on the technology. A paper on the shape-shifting material is slated to be published at the end of the month in the Proceedings of the National Academy of Sciences.
Although the technology hasn’t moved off the lab bench, Mr. Langer says its existence is the first step toward new applications, such as “intelligent stents,” for example.
Stents are small metal tubes used to prop open clogged heart arteries after they have been cleared. The material could in theory enable a stent that takes an oval shape for insertion, then transforms to a fully inflated round shape upon implantation.
It could also be an option for placing stents in hard to reach places where a single heart vessel branches into two. Cardiologists usually have to alter a stent’s shape to fit the angle of the vessel by using multiple stents that often overlap one another to cover the lesion.
“I think any kind of minimally invasive surgery where you put something through a small hole and when it gets to body temperature it changes to another shape” is a potential fit for the technology, said Mr. Langer. “And I suppose if you wanted to remove it you could go to a third shape,” he said.
This is not the first time Mr. Langer, or Mr. Lendlein, shifted the shape of plastic. The two have worked together to develop a dual-shape class of materials. Their work led to the creation of a “smart suture” that changes form as needed for surgery. Again, just add heat.
Among the potential uses is the ability to have a suture that self-ties itself. After forming a loose knot, the ends of the suture can be fixed, as a knot tightens, after applying heat. It could be the answer for doctors looking to knot a suture in a tight space.
In September, Germany-based company mNemoscience signed on to develop the suture for the commercial market.
The series above illustrates the triple shape effect of a fastener consisting of a plate with two anchors prepared from CL(50)EG: Starting at 20 degrees Celsius, the device, in an easily-handled form, is put into a scaffold, right, which might be difficult to access (a). Increasing the temperature to 40 C triggers unfolding and positioning into the cavity, left (figures b to d). Increasing the temperature to 60 C enables the anchors of the fastener to open and to couple the device into a well-defined position (e to f). In both series, above and left, the material CL(50)EG used to produce the demonstration object is a two-phase polymer network consisting of 50 percent poly(ethylene glycol) (PEG) by weight and 50 percent poly(e-caprolactone) (PCL) by weight.
A series shows the triple shape effect of a tube prepared from a polymer network, CL(50)EG. Starting at 20 degrees Celsius, shape (a) has an upright diameter of 4.5 mm; when heated to 40 C, it switches to a second programmed shape (b) with a diameter of 6.9 mm, and then to its permanent shape (c) with a diameter of 5.8 mm, when heated to 60 C. In both series the material CL(50)EG used to produce the demonstration object is a two-phase polymer network consisting of 50 percent poly(ethylene glycol) (PEG) by weight and 50 percent poly(e-caprolactone) (PCL) by weight.