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 shape, eg. melt, at high temperatures. What’s special about some of them is 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 thermochromic pigments and a few materials they have been incorporated into, namely paint, fabric, film and glass.

Thermochromic Pigments change color when exposed to heat and turn back to their original color when the temperature drops again. According to TEP:

Most thermochromic materials are based on liquid crystal technology. At specific temperatures the liquid crystals re-orientate to produce an apparent change of colour. The liquid crystal material itself is micro-encapsulated - i.e., contained within microscopic spherical capsules typically just 10 microns in diameter. Billions of these capsules are mixed with a suitable base to make thermochromic printing ink or, for example, plastics destined for injection molding.

These pigments can be mixed with an acrylic base or screen printing ink. At room temperature the pigment appears in its original color, but at temperatures between 27° and 30°C (80° to 86°F) this color disappears, eg, if a black pigment is applied to a white surface, the surface turns from black to white at the change-over temperature. When mixed with an acrylic base each pigment will turn instead into the color of the acrylic base or color blender, eg., if a blue pigment is mixed with a yellow acrylic base the resulting color will be green, but at the change-over temperature the blue will disappear and the green will turn into yellow. The ratio of acrylic base to coloring pigment depends entirely on the application and density of color required. For a detailed explanation of the functioning and applications of thermochromic pigments see the TEP Smart Colors info sheet (PDF) and this little demo animation.

Shi Yuan’s thermochromic wallpaper

Temperature-Sensitive Glass results from the application of thermochromic pigments to glass tiles which change color based on ambient, body or water temperature:

The textured glass surface layer protects and highlights the color-change film on the tile. The base color of the tile can match almost any color, and the temperature change point can be fit to the user’s environment and requirements. The dynamic color change begins at the selected activation temperature and shimmers through three phases, one with each 6–10° rise in temperature. Once the temperature peak is passed, the base color returns and remains the same until the temperature drops.
(source: Inventables)

Temperature-sensitive glass tile (image by Inventables)

Thermochromic Film has adhesive on one side and thermochromic ink on the other. The film is normally black but changes to bright green/blue at temperatures between 29.4 and 33°C (84º - 91º F). Due to its low change-over temperatures, touching a piece of thermochromic film for a few seconds will cause the contact area to change color - it can also be used with nichrome or any other heat source.

Thermochromic film (image by Mindsets)

Suppliers
Body Faders (US) :: thermochromic fabric
Inventables (US) :: thermochromic fabric, thermochromic film, temperature-sensitive glass tiles
Mindsets (UK): thermochromic pigments, thermochromic film
Paint with Pearl (US) :: thermochromic pigment powder

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

>> about the materials 101 series.

Today it’s possible to print organic field transistors (OFETs), organic light emitting diodes (OLEDs), and other devices using sophisticated laboratory equipment. But why should academics have all the fun? The goal of this project is to design a fabrication process that allows MakerBot owners to print their own electronics using (ideally) inexpensive and easy-to-source materials. In the first phase of the project we are using a RepRap, plotter pens, and research grade materials to create devices. The second phase of the project will focus on exploring new device materials. This is an ongoing project and we are looking for collaborators.

Mr. Kim and Sarik experimented with a variety of conductive materials (silver ink, P3HT, CP1 resin), which they inserted into rapidograph and pigma micron pens. According to the researchers, this is a nine step process:

The project doesn’t yet have a website but, in the DIY spirit of this research, Mr. Kim uploaded the field effect transistor patterns to Thingiverse and made the talk’s slides publicly available at mrkimrobotics.com.

All photos provided by John Sarik and Mr. Kim. John: thank you so much for discussing this fascinating research with me and for sending us the presentation materials.

How to bend sheets of polymorph-

How to add colour to polymorph-

I keep thinking that even though we tend to use conductive fabric and other soft circuits materials mostly for wearables and such, there has to be much more to it than that. Ayman’s drumsticks are a great of example of other interesting applications for these materials. He made them for his iPad iSteelPan application, but they’ll work on any capacitive surface.

The iSticks are made out of pure copper polyester taffeta fabric (I bet conductive lycra would work really nicely too), metal rod, string, and cotton pads. Check out Ayman’s instructable and make your own!

(via Alicia Gibb)

I’ve learned that there are 3 main challenges in working with soft circuits. The first one is to create circuitry with materials that are almost always completely exposed: a lot of thought goes into the layout of the circuit to not only avoid accidental shorts during normal wear, but also to avoid crisscrosses between conductive materials within the circuit layout. The second one is to think in 3D: more often than not your circuit can’t be applied to a single flat surface and you have bits and pieces spread out over several areas or layers of the piece. The third one is to find ways to connect hardware with soft conductive materials: sometimes you just need to use hard electronic components or a board.

The first two challenges have to be addressed on a case by case basis, but I’ve been experimenting with some methods to address the third that might be useful to others - I’m also hoping for suggestions on different methods and/or ways to improve these :)

:: The curled legs method
This is the classic method everyone working with soft circuits knows and loves. You simply curl the legs of any long leg electronic component, forming a little ring you can then sew to. I’ve used this method with LEDs, transistors (careful, the legs on transistors break very easily), resistors, photoresistors, and even electrical wire.

Since my conductive thread frays a lot and tends to come loose after a while, I usually finish it up with a drop of wire glue (more about this below).

When I really must use electrical wire, which is the case when working with EL wire, I prefer the stranded kind, which is more flexible that the single-strand. In this case, the first thing to do is twist all the small-gauge wires together and then apply a bit of solder to bond them. After forming the ring, apply some more solder to it in order to get a more solid shape to sew to.

:: The wire glue + snaps method
I’ve often found myself in a situation of having to work with conductive pads, which leaves out the preferred curled legs method. So I made a few experiments and found out that wire glue is perfect for these situations. Unlike conductive ink and conductive epoxy, wire glue is very cheap. It’s also easy to obtain and work with. While wire glue is not particularly good as a glue, it is a very reliable conductor.

Gluing the fabric or thread directly to the pads never really worked for me: it comes off too easily and I haven’t found a good way to reinforce the bond. But metal snaps are just perfect for the job!

Metal snaps on surface mount battery holder

I apply a bit of wire glue to the conductive pad and then, using tweezers, carefully place the male half of the snap on top of it. Just the wire glue wouldn’t be strong enough to keep the snap there once you start snapping and unsnapping your circuit. But, after the wire glue has cured (leave it for a few hours), you can add a couple drops of super glue. This doesn’t affect the conductivity or the connection and ensures a pretty strong bond. Once that’s done, you can just add a strip of conductive fabric to the soft part of your circuit and, using conductive thread, sew the other half of the snap on it.

Metal snaps on board

:: The surface mount + wire rings method
This is very similar to the method described above, except that instead of using snaps you’d strip a piece of electrical wire, make a little ring with it, and solder the ring to the contact pads. This is tricky to do on very small components, such as surface mount LEDs, but not complicated at all with bigger pads.

Wire rings on surface mount battery holder

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.

EL wire (electroluminescent wire) glows when an alternating current is passed through it. Unlike LED strips, EL wire is not a series of light points, but an unbroken line of visible light. It can be used in a variety of applications, from vehicle instrument panels and safety/emergency lighting to decoration and clothing.

EL wire works with alternating current (AC) and thus requires a driver, aka an inverter, in order to convert the batteries’ direct current (DC) into AC (in the range of 100V).

:: what is it exactly?
:: what for?
:: selecting an inverter
:: wiring EL wire
:: resources
:: tutorials
:: suppliers

What is it exactly?
Electroluminescence (EL) is an optical and electrical phenomenon in which a material emits light when electrical current is passed through it or when exposed to a strong electrical field.

EL wire consists of 4 or 5 concentric layers, each performing a different function. In the center is a solid copper conductor coated in phosphor, around which are wrapped two very fine conductive wires, followed by a clear protective sleeve (not present in 1.2 El wire), and a colored PVC sleeve. In some products, such as glowire, the wire is first covered in a clear PVC coating and then a layer of colored vinyl. Current flowing through both the core and the two thin copper wires creates an electrical field and causes the phosphor to glow. The outer plastic sheaths filter the light produced by the phosphor and provide protection (many phosphors are highly sensitive to moisture).

EL wire is available in several diameters, the thinnest being 1.2mm (aka angel hair) and the widest being 5mm (has UV protection, suitable for outdoor use and long term display). Larger diameters are more durable and (usually) produce a thicker glow, while the thinnest (1.2 to 1.5 mm), even though not suitable for harsh conditions or when weight is a factor, are more flexible and easier to bend and shape. The Live Wire Store has spec sheets for several diameters of EL wire.

The brightness of EL wire is roughly proportional to the frequency of the inverter used to drive it: the higher the frequency, the brighter the glow, and vice versa. It never burns out, but it does burn down. According to glowire, their EL “powered at 4000hz will retain brightness for approximately 1600 hours, while 400hz power will last over 5600 hours. Although the wire never does actually burn out, it does become dimmer.”

EL is also available in a variety of colors which are determined by the combination of the phosphor glow, frequency of the applied power, and the colored plastic layer. The spectrum produced by some types of EL wire can vary significantly with the frequency, while those that are filtered (have a colored plastic sheath) vary less. The aqua/ice blue wire is the most sensitive to frequency, and its color can be changed from deep green to deep blue by varying the frequency from 60Hz to 6Hz. The color of EL wire also depends on whether it’s lit or unlit (for example, yellow angel hair looks orange when unlit), and suppliers will usually provide images of both states.

What for?
- Illuminated fabrics and garments
- Light sculptures
- Safety and emergency lighting
- Decoration
- Anywhere where a continuous strip of light is desired :)

Selecting an inverter
Different types of inverters run on between 1.5V and 18V, depending on how much power they output. The selection of an inverter depends on the brightness desired (the higher the frequency, the brighter the wire) and the length of EL wire, i.e. the longer the strand of EL the more high power the inverter required to drive it. Suppliers will usually tell you the length range for each inverter (there’s a minimum and a maximum). So, in order to select an inverter for your project, you need to first know the length of EL wire you’ll be working with.

2xAA 1.5Vdc, 4500Hz, 0.5-2.5m (1.5′-7.5′) inverter

When using several strands of EL wire with a single inverter you should simply add the lengths of each strand and make sure the total is within the range of the inverter. For example: an inverter for 5m to 12m can be used to power a single 8m strand of EL wire or 8 x 1m strands.

El wire inverters usually make a slight humming noise, which is the audible sound of the frequency.

Wiring EL wire
Plug & Wear has two very good tutorials on how to wire EL, one using metal ferrules and the other connecting the EL wire directly to a (flexible) PCB. I’ve found that even though the PCB method can be very useful when connecting several wires to a single inverter, it’s also very fragile: after some handling the two thin copper wires tend to break and the soldering pads on the flexible PCB tend to come off. To strengthen the connection I’m currently using a combination of the two.

0 :: Materials & Tools
- EL wire
- Uninsulated ferrules
- Electrical wire
- Heat shrink tubing
- PBC (flexible or otherwise, only useful when wiring several strands of EL to a single inverter)
- Wire strippers
- Soldering iron (and solder)

1 :: Strip a piece of the PVC layer on one end of the EL wire, you’ll see two thin copper wires wrapped around the phosphor layer. If your EL wire has two plastic coatings (one clear and one colored), you’ll need to strip both in order to have access to the copper wires. I’ve found that many wire strippers are too aggressive for this job and end up cutting/damaging the thin wires. This is kind that seems to work well. Then, using a knife, scratch off a piece of the phosphor layer at the tip of the EL strand

2 :: Bend back the two thin copper wires and slide a metal, uninsulated ferrule over them and around the tip of the PVC sleeve. Crimp it and solder an electrical wire to the exterior of the ferrule.

3 :: Solder another electrical wire to the exposed copper core.

4 :: Slide the thinnest heat shrink tube over the ferrule. Shrink it by exposing it to heat (I like a hair drier since I’ve already messed up a few EL wire connections by using lighters and soldering irons). Take the widest heat shrink tube, slide it over the whole connection, and shrink it too.

5 :: If you’re wiring only one strand of EL to an inverter, skip this step and move on to the next one. If you’re connecting several strands of EL to a single inverter some kind of board will be useful. Plug & Wear offers a flexible PCB but, depending on the purpose, you can use any PCB or perfboard. Simply solder each wire coming out of the EL to a row on the board. Then solder two more electrical wires to each row, which you’ll use to connect the board to the inverter.

6 :: You now need to connect your EL wire/board to the inverter. If your inverter has an on/off button, make sure it’s off. Remove the batteries or unplug it from the wall socket. Simply put: make sure your inverter is not powered in any way before doing this.

To make a permanent connection between the EL wire/board and the inverter, start by sliding a heat shrink tube over each of the wires coming out of it. Solder each of the two electrical wires coming out of the EL wire/board to each of the two wires coming out of the inverter (there’s no polarity on EL wire). Slide the heat shrink tubes over the connections and shrink them. I like to use two layers of heat shrink or electrical tape, to make sure it’s all properly insulated.

Resources
:: Inverter comparison chart - Glowire
:: EL wire spec sheets - Live Wire Store
:: What is EL wire - Elwire.com

Tutorials
:: How to connect EL wire - Plug & Wear
:: Connecting EL tape to a PCB - Plug & Wear
:: How to terminate EL wire - Plug & Wear
:: Soldering EL wire - NeonString
:: Soldering EL wire - Live Wire Store
:: Soldering EL wire - Cool Neon
:: Make a glowing, wearable, EL-wire, blinky light using open source tools - Makezine
:: How to add EL wire to a coat or other garment - Instructables
:: How to make EL Wire Art - Instructables

Suppliers
:: CooLight (USA)
:: Cool Neon (USA)
:: Elec2Go (Australia)
:: EL wire online (Canada)
:: Farnell (UK)
:: Glow Authority (USA)
:: Glowire (USA)
:: Light by Wire (Germany)
:: Light’N Wire (USA)
:: Live Wire Store (USA)
:: MindSets (formerly MUTR) (UK)
:: NeonString (USA)
:: Plug & Wear (Italy)
:: That’s Cool Wire (USA)

Share your knowledge
If you’d like to contribute content or corrections regarding EL wire, please use the comment form below or add them directly to the openMaterials wiki:
materials/electroluminescent/EL wire

>> about the materials 101 series.

The book is controversial, as many of the experiments contained in the book are now considered too dangerous for the general public. There are apparently only 126 copies of this book in libraries worldwide. Despite this, its known as one of the best DIY chemistry books every published.

It was also a source of inspiration to teenager David Hahn, who tried to collect a sample of every chemical element and also built a model nuclear reactor in his back shed in the 1990’s.

Because it was published in 1960, before the US copyright laws were rewritten, and the original copyright was never renewed, it’s legal now to share it with you online.

openMaterials has cached it here, and you can also download it here and at scribd. The pdf contains 114 scanned pages and is 27.9mb.

Below is the table of contents-

In addition to a very interesting OLED tutorial, the Materials Research Science and Engineering Center (University of Wisconsin) also has online a video lab manual with step-by-step procedures, from basic to advanced, for working with nano materials.

(via Erik De Bruijn)