scientists discovered that certain metallic compounds exhibited

8/14/2019 Scientists Discovered That Certain Metallic Compounds Exhibited

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Shape memory Alloyshttp://www.azom.com/Details.asp?ArticleID=1542

BackgroundThe technique of keyhole surgery minimises scarring, speeds healing and

reduces the risk of infection. However, it is extremely difficult to carry out

delicate surgical procedures accurately in a confined space, such as implanting

a bulky device or knotting a suture with the right amount of tension. In the

latter case, if a knot is pulled too tight, necrosis of the surrounding tissue can

occur, but if it is too loose, the incision wont heal properly and scar tissue

develops.

Innovative New Suture Material

That situation is about to change, thanks to an innovative shape shifting

plastic that, according to its developers, Dr Andreas Lendlein and Dr Robert

Langer, could be fashioned into novel medical devices such as smart surgical

sutures that allow an optimised tightening of the knot. This shape memory

capability could also allow bulky implants to be placed in the body through

small incisions or perform complex mechanical deformations automatically in a

confined space. In addition, these polymers are biodegradable, which means

they breakdown after a certain time period when inserted into the body,

eliminating the need for a second operation to remove the sutures or implant.

These applications show significant progress in the medical treatment of

human beings, says Lendlein, Managing Director of mnemoScience GmbH.

The introduction of such medical devices would benefit patients and allow for a

dramatic decrease in the overall cost of treatment.

Shape Memory Materials and Medicine

Shape memory materials, which take one form at a certain temperature and

transform into another shape when heated, are not new, but until now, no such

plastics have been used in medical devices or proved to be biodegradable. To

our knowledge, there is no other company producing polymers with such good

shape memory properties combined with biodegradability, says Lendlein.

As early as the 1930s, scientists discovered that certain metallic compounds

exhibited the shape memory effect when heated above a transition

temperature. Since then shape memory alloys (SMAs), such as the nickel-

titanium alloy Nitinol, have found uses in actuators and medical devices such

as orthodontic wires that self-adjust and stents for keeping blood vessels open.

However, despite their broad range of applications, SMAs are expensive, non-

degradable, and in many cases lack biocompatibility and compliance, only

allowing for a deformation of about 8% for Ni-Ti alloys - this new material allows

deformations between permanent and temporary shape of up to 400%.

Composition of the Shape Memory Polymer

The new smart plastic is composed of two components with different thermalcharacteristics, oligo(-caprolactone)diol and crystallisable oligo(-
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Only basic research with the material has been completed so far, and more

detailed studies are needed before the polymer-with-memory material can be

tested in humans. To commercialise the new polymer, Lendlein and Langer

have co-founded mnemoScience in Aachen, Germany, which plans to produce

scaffolds for engineering new organs and stems. The researchers have already

demonstrated the feasibility of this application by getting a long fibre of the

material to transform into a corkscrew shape, typical of a stent. Such stems

could be compressed and fed through a tiny hole in the body into a blocked

artery. The bodys warmth would trigger the polymers expansion into its

original shape, and over time it would dissolve in the body.

Other Uses for Shape Memory Polymers

We are working on biodegradable and nondegradable polymers, says

Lendlein. Our aim is to transfer the results of our research into various

products. The biodegradable shape memory polymers are useful in medicine

and the non-degradable polymers in other technical applications. According toour future plans, the first product released will be a non-medical one in about

two to three years. Potential non-medical applications envisaged by Lendlein

include carrier systems for cosmetic and beaus care products, optical,

electronic an mechanical parts for control systems and recycling concepts, and

the repair of accident damage o cars. The body of a car can be restored to it

original shape simply by applying heat, such a that produced by a hairdryer,

he says.

The Future for Shape Memory Polymers

Whatever applications they are needed for new materials will play a key role inthe development of new technologies in the next century. In the field of

medical engineering, number of new technologies can only b realised if the

biocompatible materials require can be developed, believes Lendlein. In this

context, this extraordinary invention of biocompatible and biodegradable

polymers with shape memory properties is just on development in an important

group of new materials for the 21st century.Primary author: Andreas LenleinSource: Abstracted from Materials World Vol. 10. no. 7, pg. 29-30 July 2002.

For more information on this source please visitThe Institute of Materials, Minerals and Mining.
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scientists discovered that certain metallic compounds exhibited

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