LED Dragon Kite by Jie Qi

Jie Qi, from MIT’s High-Low Tech group, posted a couple really nice tutorials on how to combine paper, electronics and smart materials to create beautiful objects.

The LED dragon kite: http://hlt.media.mit.edu/?p=1414
SMA origami crane: http://hlt.media.mit.edu/?p=1448

Heat Reactive Materials
Heat reactive materials change state, shape and/or color when exposed to temperatures above ambient. Naturally, many materials change state, eg. melt, at high temperatures. What’s special about some of them that their state, shape and/or color can be altered at relatively low temperatures (provided through hot water, body heat, hair dryers, ambient heaters, ovens, or just a hot summer day), making them easy to use and suitable for DIY projects. In this post I’ll go over polymorph, shape memory polymers and heat-shrink materials.

:: polymorph
:: shape memory polymers
:: heat-shrink (tubing and thread)
:: suppliers

Polymorph, aka polycaprolactone, is a biodegradable polyester with a low melting point of around 60ºC (140ºF). It can be heated with just hot water then molded by hand or cast. Once it cools to room temperature, polymorph becomes a hard, nylon-like plastic, which can be reheated and reshaped any number of times.

“Molding a Handle” tutorial by Inventables

Polymorph is extremely easy to use. Start by filling a container with very hot water. Add some polymorph granules and wait until they turn clear and cluster together. At this point, the polymorph is ready to be shaped. Scoop it out of the hot water bath (with tongs or something like that) and shape it by hand or press it into a mold (see video above). Once molded let the polymorph cool completely - you’ll know it’s ready when it turns back to solid white. You can also melt polymorph with a hair dryer or a heat gun, but avoid using flames (such as a lighter) as this will blacken the material. Powdered pigments such as this one can be used to color polymorph.

ECCEROBOT with polymorph ‘bones’ (images by France Cadet)

Shape Memory Polymers (SMP) can be re-shaped when exposed to heat and will retain this new shape after cooling down. But once exposed again to the change-over temperature the polymer will revert back to its original shape. The physical properties, behavior and change-over temperature vary greatly from SMP to SMP. According to Wikipedia:

SMPs can retain two or sometimes three shapes, and the transition between those is induced by temperature. In addition to temperature change, the shape change of SMPs can also be triggered by an electric or magnetic field, light or solution. As well as polymers in general, SMPs also cover a wide property-range from stable to biodegradable, from soft to hard, and from elastic to rigid, depending on the structural units that constitute the SMP. SMPs include thermoplastic and thermoset (covalently cross-linked) polymeric materials.

Shape memory plastic sheet (image by Inventables)

Shape memory polymers have been finding several industrial applications, such as CRG’s Smart Mandrels:

When heated above the transition temperature, the mandrel becomes elastic and can easily be molded into a desired shape. Once cooled, the material will become rigid and retain the new shape. The mandrel can then be filament wound and the resulting part cured on the mandrel. Heating the mandrel above its transition temperature after the part is cured makes the mandrel elastic again and easily extractable from the part. Because of the mandrel’s shape memory properties, it can be returned to its original tubular shape and reused.

Heat-Shrink Tubing is manufactured from a thermoplastic (such as nylon or polyolefin) which shrinks when exposed to heat. It’s used mostly to insulate wires, connections, joints and terminals in electrical engineering. According to Wikipedia:

According to the exact material used, there are two ways that heat shrink may work. If the material contains many monomers, then when the tubing is heated the monomers polymerise. This increases the density of the material as the monomers become bonded together, therefore taking up less space. Accordingly, the volume of the material shrinks. Heat shrink can also be expansion-based. This process involves producing the tubing as normal, heating it to just above the polymer’s crystalline melting point and mechanically stretching the tubing (often by inflating it with a gas); finally, it is rapidly cooled. Later, when heated, the tubing will relax back to the un-expanded size. The material is often cross-linked through the use of electron beams, peroxides, or moisture. This cross-linking helps to make the tubing maintain its shape, both before and after shrinking. For external use, heat shrink tubing often has a UV stabilizer added.

Heat-shrink tubing

To use simply run the wires, or whatever you wish to enclose/insulate, through the heat-shrink tubing and then apply heat with a heat-gun or lighter, this will cause the tubing to shrink and mold itself around the wires. This shape change is irreversible, i.e. once shrank it’s not possible to revert the tubing back to its original shape.

Heat-Shrink Thread, which is made of polyester, looks and sews just like regular thread but when exposed to heat (176ºC/350ºF) shrinks 10 to 30% (depending on composition). To use, start by stitching normally and then apply heat with a household iron. See Erica’s Craft and Sewing Center for detailed instructions (clicking on the image of the thread will open a PDF with instructions)

Heat-shrink thread and textile perfboard (image by Plug & Wear)

Suppliers
Erica’s Craft and Sewing Center (US): heat-shrink thread
Inventables (US) :: shape memory polymers (sheets and strips), hand moldable plastic (aka polymorph)
Mindsets (UK): polymorph, shape memory polymer
Plug & Wear (Italy): heat-shrink thread
* Polymorph and heat-shrink tubing are common crafts and electronics materials and can be found in a variety of online stores.

Share your knowledge
If you’d like to contribute content or corrections regarding heat reactive polymers, please use the comment form below.

>> about the materials 101 series.

Empa’s EAP propelled airship with Dielectric Elastomer (DE) actuators as muscles.

photochromic pigments from mindsets

UV reactive materials, which initially have an off-white appearance, change to bright colors when exposed to UV rays (sunlight or a UV lamp) and revert to their original pale color when away from UV light. The basis for these materials are photochromic pigments which can be mixed with an acrylic base and then applied as normal paint. The more dilute the pigment, the less dramatic the color change.

acrylic base to orange photochromic pigment ratio tests ran by a student of the Aix-en-Provence (France) Art School

Besides pigments, which can be used to make color-changing paints, photochromic materials are also available in the shapes of sewing and embroidering thread, plastic goods such as beads and buttons, and nail polish. Naturally it’s also possible to produce photochromic fabrics, but I haven’t been able to find them as raw materials in retail shops.

photochromic thread and beads (indoors and outdoors)

What is it exactly?
According to Wikipedia:

Photochromism does not have a rigorous definition, but is usually used to describe compounds that undergo a reversible photochemical reaction where an absorption band in the visible part of the electromagnetic spectrum changes dramatically in strength or wavelength. In many cases, an absorbance band is present in only one form. The degree of change required for a photochemical reaction to be dubbed “photochromic” is that which appears dramatic by eye, but in essence there is no dividing line between photochromic reactions and other photochemistry.

Suppliers
:: Mindsets (UK): photochromic pigments and sewing thread
:: Solar Active (USA): UV reactive sewing and embroidering thread, plastic goods (beads, buttons, etc.), nail polish

Share your knowledge
If you’d like to contribute content or corrections regarding UV reactive materials, please use the comment form below.

>> about the materials 101 series.

If you haven’t yet, check out this great blog post on recycling of 3D printing materials by i.materialise’s Joris Peels:

Last week in a comment, Paul asked me, “When will more eco and sustainable materials be available for use in these printers? Something like hemp plastic or other biodegradable materials? What are the technical limitations and who is working on them?” His question was a bit too big for a comment so I’m trying to answer it here. Below I outline, very broadly, four mayor developments in recycling and 3D printing. These developments are: recycling existing 3D printing materials, using materials that are already recycled as 3D printing materials, bioplastics & recycling on location.

MAKING STUFF: Stronger, Smaller Cleaner, Smarter is a four-part PBS television series focusing on materials science:

While reports on “smart materials” or “bionic humans” are familiar enough from TV news and magazine shows, Making Stuff will be the first documentary to provide the basic science behind these and many other technology breakthroughs. Each of the four one-hour public television programs – Stronger, Smaller, Cleaner, and Smarter – will embrace developments in traditional and emerging materials as well as current research in rapidly expanding fields such as nanotechnology and biomaterials. This series will also explore the human stories that helped shape important breakthroughs in the past – the visionary talent, sheer luck, and dogged determination that turned a wild idea into a useful material.
>>Materials Research Society

For more details check out the Materials Research Society and PBS/NOVA websites.

How to bend sheets of polymorph-

How to add colour to polymorph-

If one uses latex emulsion, it is possible to get with 2 layers rubber-like material. Usually instructions say that one should dip a form into latex, but i created a cast from clay. Plus i added some color pigments for achieving better color.

The worldwide first EAP propelled airship was made at Empa in collaboration with aeroix GmbH and the Technical University of Berlin. This lighter-than-air vehicle with 8 m in length consists of a slightly pressurized Helium filled body of a biologically inspired form with Dielectric Elastomer (DE) actuators acting as muscles and deforming the body and tail fin in a fish-like manner.

Empa is an interdisciplinary research and services institution for material sciences and technology development within the ETH Domain.

The device builds a series of simulations of a growing onion plant by means of three-D scanning and printing, outputting one image every twenty-four hours from one of three angles. A fused deposition modeler that uses ABS plastic as its material is running simultaneously with a laser scanner that scans the onion. The output of this process appears rather mechanical and barren, displayed as it is at regular intervals on a conveyor belt that loops away from the scanning/printing mechanism, around a roller and back.

It was recently awarded 3rd prize at VIDA 12.0, and has now just won the grand prize in the art division at the 13th Japan Media Arts Festival.

David’s website has a great video and also time lapse sequence of the work.