Shape of treatment to come

A development in shape-memory polymers promises to pave the way for many interesting new applications in medical technology, according to its developers. The resultant polymer is claimed to be a first: one that can be deformed simply by the application of a magnetic field.

The researchers at the German Institute of Polymers and the Institute of Polymer Research in Teltow, near Berlin, are using two thermoplastic materials as the basis for the polymer, each designed for a different application.

The first, polyurethane, is a thermoplastic material often seen in conventional shape-memory polymers. But researchers are also utilising a ‘multiblock copolymer’ which has a unique property that will make it extremely useful for medical applications: it dissolves within the body.

Magnetic nanoparticles of iron oxide, no more than 50nm in diameter, are then incorporated using an extrusion process. Upon application of an alternating magnetic field the particles convert the energy in the field into heat. This heat warms the surrounding material and actuates the shape-memory effect. The amount of heat generated or magnetic field required can be set by varying the proportion of nanoparticles embedded in the polymer.

Project leader Prof Andreas Lendlein from the Institute for Polymer Research said: ‘Most polymers use temperature as the stimulus to return to their original shape. However, our new polymer will mean that the shape-memory effect can be activated without any direct contact with the material. This is an important distinction, and opens up a number of interesting possibilities.’

Lendlein believes this could open up important new applications particularly in the medical field. ‘Initiating the shape-memory effect without contact is important when you do not have access to the material or if you do not want to apply heat to the surrounding environment,’ he said.

One potential application is remotely controlled catheters that can rinse, fill or drain organs without the need for invasive or painful surgery. According to Lendlein the polymer could also be used in particularly complex machinery where access to switches or actuators is severely limited.