ETextiles rely on the existence of electrically conductive fibers, threads and fabrics that can be used in combination with textile techniques such as sewing, weaving and knitting. Most of these conductive materials are produced by industry for anti-static and EMF shielding purposes. The development and production of materials for crafting soft circuits and sensors is a more recent development.
Most conductive textile materials are based on the blending of metals for their conductive properties, and other fibers (natural or synthetic) for their mechanical properties such as flexibility and tensile strength.
As makers, we spend much of our time with the materials of our practice. We get to know them, and they shape not only the things we are able to make, but also what we are able to imagine.
The following post is a selection of (our favorite?) conductive materials based on the following aspects:
+ frequency of use (we use these materials often in our own etextile practice)
+ origins (we have some access to information about the sources and production of these materials)
+ accessibility (affordable and available to purchase)
+ variety (a bit of everything)
Working in etextiles, many of our staple materials are natural and synthetic fibers, threads, yarns and fabrics made conductive through the addition of metals, carbon or conductive polymers.
What can we know about these materials from examining them with our own senses? From using tools to take a closer look (under the microscope), or a different look (with help of a multimeter), or an informed look (researching into their datasheets and information provided by their manufacturers)?
The following information is an accumulation of knowledge from various sources, but mostly from the time spent working with these materials.
+ check out our Meet the Materials youtube playlist where we introduce a new material in each episode >> https://youtube.com/playlist?list=PLxMxh4ORY0EXqKCfkEE-xeDFXqGAS_0GI
SUMMARY
ETextiles rely on the existence of electrically conductive fibers, threads and fabrics that can be used in textile techniques such as sewing, weaving and knitting.
Most conductive textile materials are based on the blending of metals for their conductive properties, and other fibers (natural or synthetic) for their mechanical properties such as flexibility and tensile strength. Here are some of the most common etextile fibers, threads and fabrics:
Conductive FIBERS / FILAMENTS / WIRE
Metal fibers: mostly steel, as these are very strong and can be spun.
Metal filaments: very long strands that are extruded (like wire).
Thin-rolled metal filaments
Metal particles (usually copper or silver): can be applied to non-conductive materials by electroplating and plasma coating. The smoother the surface of the inert material, the better for a continuous conductive coating, that is why mostly synthetic fibres are coated in this way.
Conductive THREADS / YARNS
Steel threads: are spun from long steel fibers. Can also be spun from a mixture with other (non-conductive) fibres to increase resistance.
Metallized / metal-coated threads: non-conductive threads can be coated with a very thin layer of metal (usually synthetic because of its smooth surface).
Metal-coated filaments: non-conductive filaments can be wrapped with a thin-rolled metal wire. These are often made for decorative purposes.
Conductive FABRICS
can be woven/knitted from conductive threads or felted from conductive fibres. As with metal-coated threads, non-conductive materials (woven, knitted, felted) can also be coated with a very thin layer of metal.
OVERVIEW
>>> STEEL FIBERS, YARNS & THREADS
>>> METAL WRAPPED THREADS & YARNS
>>> METAL COATED FIBERS, THREADS AND FABRICS
>>> RESISTIVE MATERIALS
>>> OTHER CONDUCTIVE FABRICS
STEEL FIBERS, YARNS & THREADS
STEEL
made of: an alloy of iron and carbon
properties: high tensile strength, heat resistance, ferrous (attracted to/by magnetic fields), electrically conductive (but high resistance for a metal)
etextile use: because of steel’s tensile strength, yarns spun from pure or blended steel fibers are good for sewing. Because of steel’s high heat resistance and higher electrical resistance it is also a popular product for heating threads or felted surfaces.
Steel fibers are made by shaving off roughly 9cm long and 12μm diameter pieces of steel. Because steel is a metal with high tensile strength, it’s raw fibers can be spun into a pure steel thread that is flexible and strong (although it has a squeaky feel to it and loves to fray). Because steel has a high electrical resistance compared to other metals and can also withstand high temperatures, steel textile products are often used for heating.
The steel fibers can be mixed/blended with other fibers, increasing the electrical resistance because the individual steel fibers have less contact between one another. These raw fiber blends can be felted and yarns spun from such blends are great for knitting, weaving and crochetting sensors that vary their resistance based on the compression of the fibers in the material.
Producers & Products:
Bekaert is a global steel company with a specialization in etextile products and while they do not retail small amounts, you can purchase 1/2 – 1KG quantities from them. They manufacture the following Bekinox® products that we use in our work:
Bekinox VS/12 – 100% stainless steel fibres
Bekinox VN 14/2 – continuous 100% stainless steel filament yarn, Nm 4.5, Tex 250
Bekinox W12/18 – stainless steel fibers blended with wool fibers, 80% wool, 20% stainless steel
Bekinox®/Polyester – thin yarn spun from stainless steel fibers blended with polyester fibers, Nm 50/3, dTex 600, 15 Ω/cm
Bekinox®/Cotton – thin yarn spun from steel fibers blended with cotton fibers, Nm 50/2, dTex 400, 20 Ω/cm
Bekinox VS/12
100% stainless steel fibres
Bekinox VN 14/2
Continuous 100% stainless steel filament yarn
Nm 4.5, Tex 250
Bekinox W12/18
Stainless steel fibers, blended with wool fibers 80% wool, 20% stainless steel by weight
Bekinox®/Polyester
Nm 50/3
dTex 600
15 Ω/cm
Bekinox®/Cotton
Nm 50/2
dTex 400
20 Ω/cm
In their Bekaert’s about-section, they write of their process:
We purchase approximately 3 million tons of wire rod per year as our basic material. Depending on our customers’ needs, we draw wire from it in different diameters and strengths, even as thin as ultrafine fibers of one micron. We group the wires into cords, ropes and strands, weave or knit them into fabric, or process them into an end product. Depending on the application, we apply coatings which reduce friction, improve corrosion resistance, or enhance adhesion with other materials.
Bekaert history >> https://www.bekaert.com/en/about-us/history
Bart & Francis are a Belgium-based manufacturer and retailer of threads and yarns for many different purposes. In their following categories they list various steel/blend fibers and other metals blended with synthetic and natural fiber yarns:
ETextiles and Co
>> https://www.bart-francis.be/index.php?item=etextile-and-co&action=page&group_id=128&lang=EN
10% – 50% – 100% Metal
https://www.bart-francis.be/index.php?item=10_—50_—100_-metal&action=page&group_id=50&lang=EN
METAL WRAPPED THREADS & YARNS
made of: natural/synthetic filaments/fibers wrapped in copper, silver, gold, bronze….
properties: highly conducive metals blended with synthetic or natural fibers for tensile strength
etextile use: highly conductive, decorative, solderable!
Metal wrapped threads/yarns are made by wrapping a metal filament around a synthetic filament or a yarn spun from natural fibers. Historically this was done for decorative purposes. Many modern “metallic” threads are made with shiny plastic and are not conductive.
These threads make use of the combination of a highly conductive, but soft and easily breakable metals such as copper, silver and brass, and the robustness and tensile strength of synthetic filaments or threads spun from natural fibers.
Producers & Products:
Karl-Grimm is a company based in Germany that has been producing “Leonische Gespinste” (German for “metal spun yarns/threads”) since 1885. The conductive threads they manufacture are made by wrapping a thin, flat, narrow piece of metal (copper or silver plated copper) around a synthetic filament core (German: Lahnumspinnung?, English: winding). These individually wrapped filaments are then spun together in various quantities (German: Verseilung, English: stranding/twisting). Their threads that we use most are:
+ Kupfer Blank 3981 7×1 fach verseilt
Verseilung: 7×1
Lahnumspinnung: 1-fach
+ Kupfer blank 14/ooo versilbert 3981 7×1 fach verseilt
Verseilung: 7×1
Lahnumspinnung: 1-fach
Bart & Francis (mentioned above) retail the following brass metal wrapped around a cotton core:
15%metal Gimp fantasy 150 meter/cone
https://www.bart-francis.be/index.php?action=article&aid=1576&group_id=50&lang=EN
25% Metal Egypto Color Gold Gimp 150 meter/cone
https://www.bart-francis.be/index.php?action=article&aid=1631&group_id=50&lang=EN
METAL COATED FIBERS, THREADS AND FABRICS
made of: silver coated/plated synthetic fibers – synthetic fibers are used because the surface of synthetic fibers is smooth and the layer of metal can be thin and still continuous.
properties: thin, soft, nice for hand sewing, coating can wear off from the mechanical abrasion of being threaded through sewing machine or sewing needle, washing is possible but also wears away the thin layer of metal.
etextile use: use for highly soft and flexible traces and connections
This technique, also known as metal plating or metalizing, is used to coat fibers or ready-made thread or fabric in a thin layer of metal. It works best on synthetic fibers because their surface is smooth and the thin layer of metal will be continuous. The exact procedures for coating are company secrets, but we suspect it is done by some form of plasma plating or spraying-on of the metal particles, or possibly also electroplating as we observe that when etching away the metal layer there seems to be a black (carbon?) layer beneath which hints at the same technique used in electroforming (https://en.wikipedia.org/wiki/Electroforming)
Producers & Products:
Statex is a company based in Germany that specializes in coating fibers, threads and fabrics under the product range Shieldex®.
117/17 dtex 2 ply – Nylon 6.6 filament yarn coated in 99% pure silver
< 2 kΩ/m
235/36 dtex 4-ply – Nylon 6.6 filament yarn coated in 99% pure silver
50 Ω/m
Shieldex Kassel – corrosion proof copper-silver plated polyamide ripstop fabric
Shieldex Technik-tex – silver plated polyamide stretch fabric
Imbut is a German company who were spun off from the textile research institute TITV Greiz. They specialize in small-scale custom coating of textiles.
Elitex – 100% thin polyamide thread coated in silver, 110/f34/2ply_PA/Ag
OTHER CONDUCTIVE FABRICS
Besides the range of conductive fabrics produced by metal coating ready-made synthetic fabrics, other conductive fabrics are made by weaving, knitting or felting already conductive fibers, threads or yarns. All of the above listed conductive yarns and threads can be woven or knit to produce conductive fabrics with various properties such as stretch/non-stretch, conductive strips, conductive only on one side…
Producers & Products:
LessEMF is a company that does not produce, but retails a large selection of conductive mateirals for Electro Magnetic Field (EMF) shielding purposes. Unfortunately they don’t list who the original manufacturers of the products are.
RESISTIVE MATERIALS
While materials with high and stable electrical conductivity are desireble for making connections between most components within a circuit, being able to work with materials that have high(er) resistance or even vary their resistance is necessary for building resistive sensors.
Producers & Products:
The stainless steel fiber and yarn blends made by Bekaert are great for making all kinds of textile sensors that can detect pressure, stretch, squeeze, twist because as the material is compressed the fibers make increasingly better electrical contact, making the material more conductive.
3M and Caplinq manufacture carbon impregnated films, that while they are not really textile, are easy to obtain and can be integrated into textiles to make resistive sensors.
Velostat (by 3M) / Linqstat (by Caplinq) – Polymerfolie (Polyolefine), die mit Carbon Black imprägniert ist, um sie elektrisch leitfähig zu machen
more coming soon……
WIRE
Multistranded
Solid core
Enameled wire
Enameled Copper “Magnet Wire”, Kupferlackdraht
copper, enamel
ISOLATED CONDUCTIVE THREADS
MULTI-CONDUCTORS
GLOSSARY
Textile Terms
Fiber
Staple Fibers: short (cotton, wool…)
Filament Fibers: long (silk, polyester…)
Staple spun yarn
Filament spun yarn
Monofilament yarn
2Ply yarn
Thread and Yarn
Continuous, often plied, strands of fibers or filaments.
Thread vs. Yarn
Thread is for sewing
Yarn is for knitting, crochet, weaving
Ply is the number of yarns that are twisted around one another to create one single thread.
Electrical Terms
Conductive
Resistive
Piezoresistive
Insulator
Resistance and Resistivity of a Material
Resistance: the property of the material which obstructs the flow of current. The resistance of a material depends on the length, cross-section and area of the material.
Resistivity: resistance of the material which has fixed dimension. The resistivity of a material depends on the nature and temperature of the material.
Conductivity: the inverse of resistivity
Factors that Affect Electrical Resistance of a Material
+ Kind of Material
+ Temperature
+ Cross-Sectional Area
+ Length of the Conductor
Difference Between Resistance & Resistivity:
>> https://circuitglobe.com/difference-between-resistance-and-resistivity.html
Measuring Resistance
bulk resistivity
Ω·area/length
Ω·m2/m
Sheet Resistance
“ohms per square”
“Ω / sq”
” Ω / ◻”
>> https://en.wikipedia.org/wiki/Sheet_resistance
Conductive Materials
Metals are the most electrically conductive materials:
>> http://www-materials.eng.cam.ac.uk/mpsite/properties/non-IE/resistivity.html
Taken from this Table of Electrical Resistivity and Conductivity by Anne Marie Helmenstine, Ph.D., I made a selection of the most common conductive metal/materials used in etextiles.(and i hope i didn’t make any mistakes in converting numbers!)
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