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.

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.

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.

As the name indicates, electrotextiles are textiles with electrical properties. They’re mostly used for electromagnetic shielding, anti-static and heating purposes, and also for soft circuits: electric circuits or sensors made out of a combination of special fabrics, threads, yarns and electronic components.

:: conductive fabrics
:: conductive threads & yarns
:: special electrotextiles
:: related materials
:: starter kit
:: electrotextiles tutorials by openMaterials
:: learning resources
:: main suppliers

Conductive Fabrics
Fabrics with electrical properties made by blending or coating textiles with copper and/or nickel and/or silver fibers. They’re available in many textures, weaves and combination of materials. Stores such as Plug & Wear, Mindsets and Less EMF sell kits with a sample of each of their conductive fabrics. These samples provide an excellent way to get a hands-on feel for and test the properties of each material in order to find the right one for your project before acquiring it in a larger quantity. There are many types of conductive fabrics and you can find an extensive (though not comprehensive) list on the oM wiki. Here I will only describe some of my favorites.

:: Shieldit Super (iron-on conductive fabric) from Less EMF: a single side conductive fabric made of polyester substrate, nickel and copper. The back side is covered with a non-conductive hot melt adhesive, which activates at 130ºC (266ºF), meaning that it can be ironed on to another fabric, wood, glass or paper. This fabric is a pretty good conductor, easy to apply and thus perfect for making longer connections between components. It can also be cut and sewn like ordinary fabric. 230 g/m², 0.17 mm thick. UL 94V-0 level flame retardant. RoHS Compliant. Gray, 14 inch wide.

:: Electrolycra from Mindsets: looks and feels like ordinary lycra but it’s highly conductive. Its conductivity in one direction depends on how tightly it is stretched - if you pull it the resistance increases and then drops again when stretched even tighter. When cut into a thin strip, the material also warms up when current is passed through it and can thus provide the basis of a heated garment. A 6V battery will cause an appreciable warming effect. Resistivity: 5 ohms per 100mm, increasing to 20 ohms when stretched to 150mm. If the material is turned through 90º and stretched the resistance drops to 2.5 ohms.

:: Knitted Superlight Conductive Fabric from Plug & Wear: an extremely light and transparent conductive fabric, only 190 g per sq.m. It allows air flow and is easy to cut with scissors. It can also be sewn with a standard sewing machine or soldered to. Hand washable. Material: tin copper. Resistivity: 0.1 Ohm per square. Width: 1000 mm (39″), thickness: 1 mm (.039″), max working temperature: 150°C (302°F), weight: 190 g per sq.m.

:: Conductive Aluminum Laminated Fabric from Plug & Wear: a single side conductive (the shiny side) laminate made of aluminum foil and fiberglass reinforced polypropylene tape. It’s easy to cut with scissors and it can be sewn with a standard sewing machine, but it’s very stiff and calling it a fabric is a bit of a stretch. In fact it feels a lot more like a thick aluminum foil which makes it perfect for paper projects. In a recent openMaterials workshop, a group of students cut it into an beautifully intricate shape and used as a touch sensor on the cover of a book. Width: 650 mm (25.5″); thickness: 156 micron; max working temperature: 45°C (113°F); weight: 185 g per sq.m.

:: Velostat: a film made of opaque, volume-conductive, carbon-impregnated polyolefin. The resistivity of velostat decreases when pressured. When sandwiched between two conductive layers, it has a wonderful range for making pressure and bend sensors. Depending on the project, more than one layer of velostat might be necessary, eg. I used 3 layers of velostat to make a pressure sensor that gradually lights up a few strands of EL wire. Thickness: 100 microns; width: 91 cm (36″). Volume resistivity < 500 Ohms/cm. Color: black.

Conductive Threads & Yarns

Conductive threads are made of a combination of either cotton or polyester with alloys of several conductive materials such as silver, copper, tin and nickel. Just as most conductive fabrics, conductive thread is uninsulated making it excellent to connect electronic components to each other or to other electrotextiles. In order to ensure proper connection it should be sewn very tight and with more loops than normally used with regular thread. After some time, conductive thread tends to fray and the stitches to become loose. For this reason I often coat my conductive thread connections with a bit of Wire Glue. Wire glue takes several hours to cure so this coating should only be done after you’re done with all the sewing.

There are several kinds of conductive thread, with significant differences in terms of conductivity/resistivity and fraying, but they are commonly sold in two qualities: 2-ply and 4-ply. The 4-ply contains twice as much metal as the 2-ply, making it more conductive, but it’s also thicker making it harder to thread and sew with. For this reason I usually keep a set of sewing needles with large eyes. The How to Get What You Want and Fashioning Technology websites have some excellent overviews and comparisons of the conductive threads available in the market.

The resistivity of all conductive threads increases drastically with length, making them inappropriate for long connections. For this reason, consider making long connections with ribbons of a good conductive fabric and using the thread only to sew the electronic components to the conductive fabric.

The highly resistive (<1000 Ohm/10cm) silver plated thread offered by Less EMF (cat. #A1226) is good for embroidering fixed or variable resistors.

Conductive yarns are usually made of a combination of polyurethane and inox steel fiber. The resistivity of some yarns increases when the knitted piece is stretched. Again, see How to Get What You Want for great information on conductive yarn.

Special Electrotextiles
:: Textile Perfboard: a fabric base with interlaced rows of thin metal wire.

:: Pressure and Bend Sensitive Fabrics, Tapes and Buttons: made of a layer of insulating knitted or resistive fabric sandwiched between two layers of knitted conductive fabric.

:: Textile Water/Wetness Sensor: detects water by changing its resistance from an open circuit to a few megaohms.

:: EL Wire Tapes: knitted tapes with strands of EL wire weaved into them.

:: Hook and Loop Fastener: similar to velcro but conductive.

Related Materials
:: Wire Glue: even though originally created to replace solder on the connection of electronic components, wire glue is a great material for working with electrotextiles as well. I use it to coat conductive thread knots to prevent them from fraying and also to attach metal snaps to metals that can’t be soldered to.

:: EL Wire: can be basted, woven into or otherwise applied to your soft circuits for illumination.

:: Quantum Tunnelling Composite (QTC): an interesting pressure sensitive material for making textile control pads and keyboards.

:: Metal Sewing Materials: almost all metal sewing supplies, such as snaps and zippers, are conductive and can be used in conjunction with electrotextiles. See oM’s connecting hardware & softwear on soft(er) circuits blog post for some examples.

:: SMD Components: SMD battery holders, LEDs, etc that have flat metal pads are also great for soft circuits. You can solder or wire glue metal snaps or metal rings on these pads to attach them to your circuit.

Starter Kit
I’m often asked what are the first materials one should get to start making soft circuits. Here’s a suggestion for a starter kit:

:: Conductive thread
:: Iron-on conductive fabric or another non-stretch conductive fabric*
:: Stretch conductive fabric*
:: Velostat*
:: Assorted LEDs
:: CR2025 or CR2032 lithium batteries
:: SMD lithium battery holder with flat pads such as this one
:: Non-conductive fabric (felt is my favorite)
:: Sewing supplies: thread, metal snaps, needles with large eyes, needle threader
* Most electrotextiles stores sell conductive fabric sample kits, you can just try one of those instead of buying a larger quantity of the stretch and non-strech conductive fabrics.

Electrotextiles Tutorials by openMaterials
:: Connecting Hardware & Softwear on Soft(er) Circuits
:: Light Up Handshake Glove

Learning Resources
There are many resources for learning how to use electrotextiles. One of the most useful and complete, from a materials and experimentation point of view, is Kobakant’s How to Get What You Want - make sure to check out the sensors and conductive materials sections.

:: Websites w/ Tutorials
Fashioning Technology
How to Get What You Want
Lynne Bruning’s Techniques
Plug & Wear
Plusea
Soft Circuits Saturdays
Sternlab

:: Books w/ Tutorials
Fashion Geek by Diana Eng
Fashionable Technology by Sabine Seymour
Fashioning Technology by Syuzi Pakhchya
Open Softwear by Tony Olsson, David Gaetano, Jonas Odhner, Samson Wiklund
Switch Craft by Alison Lewis

:: Other Interesting Websites
3lectromode
Talk2MyShirt

Main Suppliers
:: Less EMF (USA): conductive fabrics, resistive thread, hook and loop fastener, textile pressure sensitive switches, fabric potentiometer kit

:: Mindsets (formerly MUTR) (UK): conductive fabrics & thread, but make sure to also check out the materials > smart materials section

:: Plug & Wear (Italy): conductive fabrics, textile perfboards, pressure sensitive fabrics, tapes and buttons, textile water/wetness sensor, conductive thread and yarns, EL wire, EL wire tapes

:: Sparkfun (USA): several types of conductive thread

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

>> about the materials 101 series.

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

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.

This mitten lights up when its wearer shakes hands with someone. It has two exposed soft contacts around the thumb and across the palm which, when bridged by bare skin, turn on the LED embedded on the flower. The mitten itself was created by fashion designer Isabel Tomás, and we then sewed a simple touch switch circuit onto it using conductive fabric and thread. It also works with high fives and holding hands :)

Isabel and I designed this as a soft circuits exercise for some upcoming materials workshops. Below you can find all the instructions and images we prepared for this purpose.

Note :: The measurements on this tutorial are for very small hands - mine :) Remember to adjust them to your glove size. Also, we used iron-on conductive fabric on our first prototype, but after some wear it started to come off, so we ended up sewing all the conductive fabric to the knitted glove.

:: What you’ll need
Materials
- yarn (or any old glove/mitten, if you don’t want to start from scratch)
- conductive thread
- conductive fabric
- self-adhesive conductive fabric (used on the batteries’ pouch, can be replaced by some non-adhesive, but stiff, conductive fabric)
- fabric or knitted flower
- regular fabric
- regular sewing thread
- 2 metal snaps
- 1 super bright LED
- 1 BC547B transistor
- 2 x 3V lithium coin cell batteries

Tools
- sewing needles
- needle-nose pliers
- scissors

:: Circuit

circuit schematics

:: Knit the mitten

If your knitting skills aren’t as good as Isabel’s you can use any store-bought mitten/glove and skip this step.

:: Add the contacts
On a hand shake the best point of contact usually happens in between the thumb and the index. But we thought it would be fun to also make it work for high fives so we extended the fabric contact strips all the way across the palm.

Cut two strips of conductive fabric approximately 0.5cm (0.2in) wide. One should be around 28cm (11in) long and the other 15cm (6in) - adjust to your glove size.

top side

Cut two vertical slits on the top side of your glove and stitch them so the glove doesn’t come undone. Do the same on the palm side. The distance in between the top and palm slits should be approximately 7cm (2.75in).

palm side

Slide the longer strip of conductive fabric in between the two slits closest to the fingers. On the inside leave an 11cm (4.3) tip on the palm side and 10cm (4in) on the top side. Do the same with the second conductive fabric strip and slide it in between the other two slits, leaving 2cm (1in) on the palm side and 6cm (2.4in) on the top side.

Sew the fabric strips in place.

:: Make the batteries pouch
This double pouch will contain the two 3V coin cell batteries. They should fit very snugly to ensure proper contact.

Cut a piece of non-conductive cotton fabric of approximately 9cm (3.6in) x 6cm (2.4in). Hem the top and bottom on the longest side: one hem should be 1cm (0.4in) high and the other 0.5cm (0.2in). Fold your piece of fabric over itself so that the 1cm (0.4in) hem sticks out. Crease the fold with the iron.

batteries’ pouch :: inside

Next, open your square of fabric and iron on 3 strips of conductive fabric as shown on the image. Use conductive thread to sew on two snap studs at the tip of the 2 parallel strips (on the 1cm/0.4in hem).

Now, fold your piece of fabric back down and, using non-conductive thread, sew the left and right sides of your pouch.

batteries’ pouch :: outside

Turn it right side out and stitch across the middle to make two compartments. The batteries should fit very snugly inside these compartments so make them as tight as possible.

Turn it around so the snaps are facing down, and using a marker write “+” on the right side and “-” on the left.

:: Sew on the top half of the circuit

glove inside out :: top side

With your glove inside out, fold and sew the longer conductive strip as shown above. Using conductive thread, sew a snap socket at the tip of the longest strip of fabric.

Cut another strip of conductive fabric approximately 5cm (2in) long. Place it so the its tip matches the position of the batteries pouch and extends horizontally all the way into the palm side of the glove. Sew it to the glove and attach the second snap socket using conductive thread.

:: Insert the LED

Insert the LED on the flower so that its legs stick out from the bottom. Make sure the legs of the LED aren’t touching each other.

:: Sew on the bottom circuit

glove inside out :: palm side
the LED is represented above as being inside the glove just so you can see where to place it, but in fact it should be embedded on the flower on the exterior, only its legs should extend into the interior.

With the glove inside out, fold and sew the conductive fabric strips as shown above.

Open the legs of the transistor and curl them slightly with needle-nose pliers.

Using conductive thread, sew the emitter of the transistor to the horizontal strip and the base to the vertical strip on the right.

Place the flower on the exterior side of glove so that the shorter leg of the LED (-) is closest to the transistor’s collector and sew them together using conductive thread.

The transistor’s legs break easily, so avoid stretching them too much and add a tiny drop of super glue to the junction area.

Sew the other leg (+) of the LED, with conductive thread, to the left vertical strip of conductive fabric.

:: Make the lining
This is absolutely necessary since it not only makes the glove more comfortable, but also avoids contact between your skin and the exposed circuit (which would cause the LED to be always on).

Use any non-conductive stretchy fabric and sew it to the glove only at the top (near the fingers slit). This will avoid contact between your hand and the circuit while still allowing you access to it.

:: Insert the batteries and attach the pouch
Insert the batteries into the pouch. The one on the right should have + facing up and the one on the left the other way around. Use the snaps to attach the pouch to the glove.

:: Done!
That’s it. Now put your glove on and go shake hands :)

* glove illustrations by Isabel Tomás
** thank you Maurício Martins and Pedro Ângelo

Methylenchlorid, also known as methylene chloride and dichloromethane, is an organic chemical compound and solvent.

It’s commonly used as an adhesive for architectural models because of its ability to bond materials transparently and quickly without sticking to your fingers.

The following plastics are suitable for bonding with methylene chloride - polystyrene, acrylic, polycarbonate, PET-G, and ABS.  Note you can’t use it to with polypropylene or polyethylene.

Here in Vienna I am able to buy polystyrene and methylenchlorid at ARCHIDELIS, which has a range of model building materials for architecture, design and fabrication.

*update 11 dec 2009*
This experiment relates to an exhibition of mine at Museums Quartier in Vienna, details are below-

Niki Passath - QUANTITY
Open: Wed 16.12.09, 19h. Exhibition closes 16.1 2010
Electric Avenue, quartier21 Electric Avenue, quartier21

From the curatorial essay-
“The title “QUANTITY” derives from the simple fact that it is an
installation containing a collection of objects that through their
shape, have the ability to expand and contract. The objects are
designed so that the continuous expansions and contractions are
“clumsy” and strenuous attempts to express movement. Over time and the
limited space of the staging results in forced collision of artifacts
to each other and the surrounding walls. As a result of which the
geometrical forms either change the direction of their movement
patterns or develop a common collective locomotion.

The diversity of interactions and collective forms that fascinate
evolve over time, before the eyes of the observer, completely without
his intervention, becoming socialized.

But what does it mean if it is possible for an artist to inscribe the
social behavior of biological forms “hijack-ing architectural bodies?
For Passath it’s just one more proof of the many possibilities of
techno-organic being.”

Quantum tunnelling composite (QTC) is a smart flexible polymer, with extraordinary electrical properties, used for pressure switching and sensing. In its normal state it’s a near-perfect electrical insulator, but when deformed QTC becomes a metal-like conductor capable of passing very high currents. In fact, a QTC button measuring 4mm square and 1.5mm thick can pass up to 10 amps when squeezed! Also, the change from insulator to conductor is dramatic and can be obtained with only the tiniest pressure.

Oh, and did I mention it’s inexpensive too?

-> Update: I recently realized that QTC pills are magnetic too. Nothing like having some magnets laying around on the table while you work :)

What is it exactly?
Unlike carbon loaded polymers, such as resistive foam, that require a lot more pressure and conduct minute currents through a percolation process (the effect of carbon particles touching within the polymer structure), QTC is made of metal filler particles combined with an elastomeric binder, typically silicone rubber. Instead of percolation this material owes its extraordinary properties to a quantum tunneling phenomenon: electrons tunnel through the material, i.e. conduct, when their physical structure is slightly changed by pressure.

QTC usually comes in the form of pills or sheet, but I’ve also encountered references to cable, ink/coating, and granule. QTC pills are just tiny little pieces of the material. The sheets are composed of one layer of QTC, one layer of a conductive material, and a third layer of a plastic insulator. While QTC sheets switch quickly between high and low resistances, QTC pills are pressure sensitive variable resistors.

What for?
- Touch switches (sheet)
- Force/pressure sensors (pills)
- Motor speed control using force (pills)

The small size of QTC pills and their rubbery nature make them particularly well suited for soft circuits. Some interesting applications include a Double Sided Fabric Keyboard and an FM Radio w/ Textile Controls.

How?
:: Making a pressure/force sensor with a QTC pill
The video below shows how to use a 4×4x1.5mm QTC button (in this case 3 connected buttons, since one was too small to be visible on the video) as a pressure sensor. A QTC button is placed on a piece of copper sheet, though it could be another conductive material, which in turn is connected to 9V. The DC motor is connected to ground and an alligator clip that is used to press the QTC button, closing the circuit.

Apologies for the awful video quality :( I need to get some new equipment.

:: Making a simple switch out of QTC sheet
Simply place your piece of QTC sheet, with the plastic side facing up, across two pieces of conductive material (see illustration above). This is your button. You can hold it in place with some tape, but don’t forget that this is a very sensitive material and too much pressure exerted by the tape will cause the switch to be on at all times. If you need to put anything else on top of it, such as a label, add a piece of foam in between the button and the label. A 3K3 resistor will produce a switch that requires moderate force and will not be triggered by light pressure.

:: Making QTC sheets from pills
The illustration above shows the 3 layers of QTC sheet. Start with a bottom layer of some insulating plastic. Glue a sheet of a conductive material on top. It doesn’t matter which or how much glue you use to attach the polymer to the conductive material, the plastic is used here only as a ‘cushion’ and insulator between the hand pressing the switch and the current. I use conductive adhesive copper track with the adhesive part facing up and superglue on the back. And then place the QTC pill or pills, depending on how large a surface you need, onto the adhesive of the copper track. If you use more than one pill they’ll have to be connected to each other.

Resources
About QTC Technology @ Peratech
QTC Applications @ Peratech

Products & Supplier
I’ve only been able to find this material at MUTR Teaching Resources (UK). They supply:
QTC Pills
QTC Sheet Holders
QTC Testing Kit
QTC CDRom
Science of QTC Booklet

Share your knowledge
If you’d like to contribute content or corrections regarding QTC, please use the comment form below or add them directly to the openMaterials wiki:
materials/pressure sensitive/quantum tunneling composite

>> about the materials 101 series.

Hot Glue (aka Hot Melt Glue, Thermoplastic Adhesive)
This must be one of my favorite materials. It allows you to glue almost anything together in an often easy and semi-durable way. It dries pretty quickly so you don’t have to wait more than a minute or so to proceed with your work. And, even though the most common color is translucent, which dries to a milky white, it comes in many shades.

Hot glue is also great for prototyping when you don’t yet have all the right materials around and you just want to quickly stick two things together, isolate a connection, fill a gap, or even cast a small object.

What is it exactly?
Hot glue is a form of thermoplastic adhesive, i.e. a polymer that is solid at room temperature, turns molten when heated, and bonds as it cools back down. Due to its temperature sensitive nature, hot glue is not suitable for use in extreme temperature environments: it may become very brittle when exposed to low temperatures and begins to soften at temperatures above 70ºC (160ºC). But this also means that it can be remelted and remoulded when needed.

This material is commonly made from combinations of ethylene vinyl acetate, resin, wax, and any assortment of polyamides, polyethylenes, polyester or polypropolenes. It’s usually supplied in solid cylindrical sticks of various diameters and lengths, designed to be melted in an electric glue gun. Most common (household use) stick diameters are 10mm (7/16”) and 7mm (5/16”). Other forms may include pellets, chips, and pillows.

Glue guns heat the glue stick until it melts. The molten glue is then fed through the dispenser by using the trigger (or manually, by pushing the unmelted portion of the glue stick into the melting chamber), and out through the nozzle. Hot glue guns may be low-temperature or high-temperature (high-temperature, low-temperature, and dual-use glue sticks are available in the market). The low-temperature version heats up to around 120ºC (250ºF) and the high-temperature to approximately 195ºC (380ºF), producing a stronger bond. Glue guns also come in a dual version with a switch for both low and high-temperature use.

What for?
Besides gluing things together, hot glue can be used for other purposes, such as:
:: Filling gaps
:: Isolating wire connections when you don’t have, or can’t use, heat shrink tubing
:: Diffusing LEDs
:: Casting material

How?
:: Basics
You’ll need glue sticks and a glue gun. Both can be found on any hardware, arts & crafts, or home improvement store. You can get fancy, but even the most inexpensive glue gun will do the trick.

Insert a glue stick into the back of the glue gun, plug it in, and wait until it gets very hot. Avoid touching the tip of the glue gun, it’ll be hot too, instead test the temperature by squirting out a few blobs of glue onto a piece of paper and checking how well they flow out of the tool. Finally, bring the tip of the gun very close to, but not touching, the surface you want to glue to and pull the trigger :)

When working with a hot glue gun, some kind scrap cardboard should be used to set the tool down. The melted glue will drip from the nozzle, especially when the gun is resting for more than a few seconds. Once it’s unplugged the glue will re-harden inside the melting chamber.

Once the glue stick is no longer visible on the back of the gun another one can be loaded right behind it.

:: Diffusing LEDs

Luminaries - Hot Glue LED Diffusion is a really nice video by Kelsey Meuse showing how to diffuse LEDs with hot glue. See also the instructable Hot Glue LED Diffusion by user depotdevoid.

:: Casting

Images from How to Cast Using Hot Melt Glue, a tutorial by Dead Pepper. And check out the Prop Making - Thermal Adhesives Are Cool! post on Dani’s Mixed Plate for very detailed instructions on how to make your mold, cast with hot glue, and paint the pieces.

Tips & Tricks from the DIY Community
Hot glue can be shaped for a couple seconds before it cools down and dries. While you’re working keep a container with some water close by. As soon as you apply the glue, dip your finger in the water and use it to shape the glue blob. The water will prevent the glue from sticking to or burning your finger.

Watch out for extreme temperature environments or placing hot glued projects near heat or cold sources: it might remelt (heat) or become very brittle (cold).

The fact that the glue remelts when exposed to heat means that, in some instances, you can fix mistakes by reheating it: let your glue gun get very, very hot and touch its tip to the blob of glue you want to remelt.

There is a patent for hot melt adhesive heating by means of microwave, but if you have a microwave and some hot glue sticks laying around…

Interesting links
This to That
a great site with advice for gluing anything to everything.
Precision Hot Glue Gun Instructable
a simple mod to turn a cheap glue gun into a precision instrument.
Hot Melt Adhesive
wikipedia’s definition.

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

>> about the materials 101 series.