Metal with memory: Chris Lefteri on smart materials


Chris Lefteri turns his attention to smart materials – plastics and metals that once altered have the ability to return to a previous form with the application of heat. Lefteri is a designer and has written seven books about new materials and their application


Blueprint

There are many materials that are defining the future: renewable resources, completely new materials such as graphene (see Blueprint 332, January/February 2014), but one of the biggest and most fascinating groups -- that continues to grow -- is smart materials.

Ezio Manzini says in his book, The Material of Invention, trying to capture a snapshot of materials is like trying to take a group photograph where everyone is continually moving. This comparison relates to smart materials in two ways: firstly that it is a rapidly changing family, and secondly that many of the smart material families are in essence about change and motion. In this spellbinding family, metals and plastics can be bent, twisted and deformed, but when heat is applied will return to an original shape that has been pre-programmed during production.

For example, imagine heating a coiled spring so that it expands and locks itself into place in a specific location within an ordinarily hard-to-access place, or a coil that unwinds itself once put into position, or a strip of material being fed through a small opening and turning up the heat so that it expands into a bigger shape. If these sound vaguely biological and medical that's because one of the largest arenas for shape-memory materials is in the medical industry, where various plastics and metals are used for intricate surgery, either as medical instruments or as implants. Furthermore, these materials are not just flimsy shape transformers: if needed to work against an external force, a 4mm-diameter actuator, for example made of nickel titanium metal alloy wire, is able to lift a tonne.

Apart from the medical industry, most applications are in engineering -- it is used for tube coupling in spacecraft, actuators in a range of industrial applications, on/off switches and thermostats. One of the main advantages is that they can replace complex or heavy motorised parts.

New York architecture practice Decker Yeadon’s shape-shifting Smart Screen and Homeostatic Facade System in action 1 2 1 &

But shape-changing materials have entered the lens of designers and architects, who are exploring practical and poetic ways to harness shape memories to create alternative energy projects through to self-disassembling mobile phones.

New York-based architect Decker Yeadon illustrates a wonderful approach to the fusion of technology and buildings with many of its projects. Its Smart Screen and Homeostatic Facade System changes shape and creates moveable facades with a seemingly living surface. This is based on R-Phase shape memory alloys that respond by opening and closing depending on changes in interior room temperature to permit or deny heat gain from the sun.

Shape memories are not restricted to this level of outward-facing application. Smart Mandrels is a process used in industrial production that uses smart tooling to create complex components that traditionally would have been difficult to remove from the template. It makes the component's shape memory and, after it has been produced, heat is introduced changing the shape in which the piece is accommodated so that it can be more easily removed. Current research is looking at how to create metals that will change shape at multiple temperature ranges, perhaps paving the way for a single tool that is completely variable.

Industrial production has yet to be fully realised but the future of shape memories could lead to a revolution in the deconstruction of objects rather than their manufacturing: one of the biggest potential areas for helping create sustainable products is to aid their disassembly. Imagine a complex office chair of electronics, plastic and glass that uses heat-activated screws that, by putting the chair in a hot tub, change shape to self-unscrew all the various components.

Chris Lefteri is a designer and has written seven books about new materials and their application

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