Shape Change Materials

Shape memory Alloys

• http://www.gzespace.com/Oricalco.html

The 'Thermal Shape Memory Alloy' is characterized by its extraordinary ability to recover any shape, pre-programmed, upon heating. Until today this light weight alloy with about 50% Titanium inside has been used in advanced sectors like space and recently in medical applications. Through the Technology Transfer Programme of the ESA, D'Appolonia has transferred this knowledge in traditional sectors. In this framework Corpo Nove, through their R&D spin-off Grado Zero Espace, have used Thermal Shape Memory metals as a fabric for the manufacturing of a shirt on with long sleeves which was made in this fabric. The sleeves fabric could be programmed to shorten immediately as the room temperature became a few degree hotter. The fabric can be screwed up into a hard ball, pleated and creased then just by a flux of hot air (even a hairdyer) pop back automatically to its former shape.

• http://www.shape-memory-alloys.com/index.html

Shape memory Alloy wire:

• http://www.shape-memory-alloys.com/wire.html

The MFC consists of rectangular piezo ceramic rods sandwiched between layers of adhesive and electroded polyimide film.

This film contains interdigitated electrodes that transfer the applied voltage directly to and from the ribbon shaped rods. This assembly enables in-plane poling, actuation, and sensing in a sealed, durable, ready-to-use package. When embedded in a surface or attached to flexible structures, the MFC actuator provides distributed solid-state deflection and vibration control.

• http://www.smart-material.com/Smart-choice.php?from=MFC

Shape memory Polymers

temperature actuator

electrical actuator (ElectroActivePolymers)

ElectroActivePolymers are plastics that expand or contract in the presence of an electric field. Cycle through these shape changes and the materials become actuators or motors that work much like biological muscles. Pump electrons into these polymers, and they can store this electricity.

light actuator

Researchers from German organizations GKSS Research Center, Rhine-Westphalia Institute of Technology (RWTH Aachen) and mNemoscience GmbH, and the Massachusetts Institute of Technology have concocted a polymer material that can be switched from one shape to another in the presence of the right wavelengths of ultraviolet light.

The material could eventually be used in industrial and medical applications, including intelligent stents and sutures. An intelligent stent could begin as a string that could be threaded into a blood vessel through a tiny incision, then activated with ultraviolet light via a fiber-optic probe to change into a corkscrew-shaped stent that would keep a blood vessel open. An intelligent suture would form a knot when activated.

The material can be manipulated into a new shape, which is fixed when the material is illuminated with ultraviolet light with a wavelength longer than 260 nanometers. The material changes back to the original shape when illuminated with ultraviolet light below a wavelength shorter than 260 nanometers. The material can be fixed into many types of shapes, including elongated films, tubes, arches and spirals. Existing light-activated shape-memory polymers are limited to expanding, shrinking and bending.

The material is a mix of two polymers. The first forms the material's original shape, and the second forms cross-links in the presence of ultraviolet light longer than 260 nanometers. Exposing the material to the shorter wavelength breaks the cross-links, which allows the material to recover its original shape. The work appeared in the April 14, 2005 issue of Nature (Light-Induced Shape-Memory Polymers).

• http://www.trnmag.com/Stories/2005/042005/Ultraviolet_shifts_plastic%27s_shape_Brief_042005.html
• http://www.primidi.com/2005/04/14.html

Following from MIT web: 'Plastics with "shape-memory"--ones that change shape in response to a temperature increase--are well known. In 2001, Langer and Lendlein were the first to report biodegradable versions of these materials in the Proceedings of the National Academy of Sciences.

A year later, the researchers introduced thermoplastic, biodegradable shape-memory polymers and demonstrated a nifty medical application--a smart suture that ties itself into the perfect knot. That work was described in the journal Science; mNemoscience GmbH of Aachen, Germany, was developed to commercialize the discovery.

"Now instead of heat, we can induce the shape-memory effect in polymers with light," said Lendlein.

Key to the work: "molecular switches," or photosensitive groups that are grafted onto a permanent polymer network. The resulting photosensitive polymer film is then stretched with an external stress and illuminated with ultraviolet light of a certain wavelength. This prompts the molecular switches to crosslink, or bind one to another.

The result? When the light is switched off and the external stress released, the crosslinks remain, maintaining an elongated structure. Exposure to light of another wavelength cleaves the new bonds, allowing the material to spring back to its original shape.

The team notes that in addition to elongated films, a variety of other temporary shapes can be produced. For example, a spiral can be created by exposing only one side of the stretched sample to light. So "while the deformation is well-fixed for [the irradiated] side, the other side keeps its elasticity. As a result, one contracts much more than the other when the external stress is released, forming an arch or corkscrew spiral shape," the authors write.'

• http://web.mit.edu/newsoffice/2005/smart-plastics.html

water actuator

Programmable/Water Actuatable Shape Memory Polymer

Nanyang Technological University propose a novel way to fabricate functionally gradient shape memory polymers, which can be actuated by water. This technique provides an approach for recovery of shape memory polymers inside, e.g., human body, without any heating system and in a programmable manner following a prescribed sequence.

• http://www.ntu.edu.sg/home/mwmhuang/smp/smpwater.htm

Shape change research

• http://www.shapememory.com/

-- Openloop. Rachel Wingfield - 05 Oct 2005
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