Kontinuum Cloth... continued

For an artist residency at Autodesk, I worked on a machine and a conductive ink to print circuits directly on textiles. Why do this? Making smart apparel scalable, functional and robust relies on automation and easy prototyping.  Most e-textile projects are done by hand, making them hard to build. Without easy iteration, it's challenging for designers to create strong prototypes that can someday become products. With this in mind, I wanted to build a  machine that could help designers create active, functional, electronic soft goods in the same way that a 3D printer can help a designer prototype a hard good. Of course, this machine is far from being an industry tool, but exploring possibilities for making e-textiles more manufacturable is the first step to a better understanding of long-term solutions. This blog post covers some elements of further developing this work with help from my teammate Ezgi Ucar and Luis Rodriguez from Three Digital Cooks.  Ezgi and I executed much of the fabrication and testing of swatches and Luis built the circuit printing machine below. It was a great improvement to my original build, which can be seen here. 

1.) THE MACHINE

A tool to print circuits onto fabric

Luis Rodriguez built a highly accurate CNC machine that extrudes conductive ink onto fabric. Where do we get the ink from? We make it. The ink is specially made to work on stretchable textiles and muslins. Many conductive inks deposit to a plastic sheeting that goes onto the fabric, but ours goes directly onto the fiber itself. This is useful because fabrics shrink, bend and flop and sometimes plastic doesn't want to move quite like the fabric does. This can cause lifting or electrical issues.

The machine can print any geometry we give it, meaning we can print circuits in an accurate way by sending the machine a file, loading it up with ink and pressing "GO". The image above shows a circuit printed onto paper.

Once we got the machine rolling, we started some experimentation. The two experiments below show how conductive ink and machines that print circuits onto fabric can be useful.


Being able to print electrodes onto fabric could mean biometric monitoring on a comfortable garment.

 

PRINTED ELECTRODES

Use Case 1

We wanted to see if our ink and printing system could work for making electrodes. We made two ink geometries that were intended to be at the proper spacing for an EMG reading. EMG reads muscle contractions, so Ezgi and I turned the printed electrodes into a small ink sleeve. We then hooked it up to an Arduino and had Ezgi flex. See the video below to see how the electrodes can read Ezgi's movements (the numbers change quite a bit). This sort of system could be much more comfortable for patients that need constant moniotoring than a gel electrode patch.

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Uploaded by Madison Maxey on 2017-05-12.

Being able to sense when a fabric is being touched could be useful for soft robotics or prosthetics. Imagine a soft robot that can sense when a human has touched it and respond.

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TOUCH SENSITIVE FABRIC

Use Case 2

We created swatches of lettering that could tell when you touched certain letters using capacitive touch (the same kind of sending your phone screen uses). In the GIF above, you can see how the LED on the fabric starts changing colors in a gentle gradient when I touch the E. When I touch the T, the pattern switches to a blinking color change.  When I touch the E again, the LED goes back to a gentle gradient.  This means the fabric is reading where I touch and then reprogramming the LED with a different output. The LED helps us see visually what's going on, but this kind of touch sensitive fabric can be useful for soft surfaces to respond to humans with kinetics, speech or other highly functional outputs.  

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That's it for this series of explorations. More to come as we continue to research e-textile production.


Choosing Conductive Threads

Choosing a conductive thread or yarn can be a challenge, as it's not always clear what one should be looking for in a conductive filament.

After inspecting a few threads on the market, we came up with a criteria for choosing a "good" thread or yarn.

This image demonstrates how more surface area can be covered with more conductive filaments.

This image demonstrates how more surface area can be covered with more conductive filaments.

1.) ELECTRONIC FUNCTIONALITY - You should aim for the thread that will apply to the most applications possible.  To us, this means the highest conductivity. Even for resistive heating,  you can create a large surface area heating element with a more conductive thread.A less conductive thread restricts the surface you can cover for just about any application.

2.) MATERIALITY - The yarn or thread you choose should be sewable, weave-able or knit-able in an industrial setting. We optimize for manufacturing at Loomia, so if the material cannot be used in a scalable way, it's not a good choice. When it comes to sewing, the thread should have a small diameter - something under .2" (based on the guide below from Superior Threads).  For knitting, choose something that won't damage an industrial machine, like Jameco 92 thread. Some manufacturers won't run course metallic threads through their CNC knitting machines, so ensure that you choose something that is safe for the threading system.

3.) CONNECTION- Ideally, the yarn or thread should should have an outer metallic coating, making it solderable. Of course, there are many ways to make connections, but having a solderable thread opens up how you can connect the thread to components.

 

 

 

 

As a whole, we haven't seen conductive thread or yarn used widely in consumer products. Aside from Sensoria Socks (which have conductive yarn knit in) or Project Jacquard (which uses a cap touch embroidered grid, many products we've seen online still use traditional wiring or use electronics techniques. For example, the image below shows normal wires with an overmolded "winged" component that allows you to sew the wires to a fabric.

 

 

Stretchable Conductive Ink

Smart clothing only works when all the enabling technologies work. Just like zippers, buttons and thread support our passive clothing, new technologies that bridge apparel and electronics can support our active clothing.  At Loomia   (the company where I work and play), we focus on developing technologies and products that can make our clothing smarter. I think great materiality is important to this industry, so stretchable, direct to fabric conductive inks useful in the sense that they support making circuited clothing feel like normal clothing.

Stretchable inks are normally deposited onto TPU . (thermoplastic polyurethane) and then onto a textile. It sounds like a promising solution, but there have been strong arguments made by Rebeccah Pailes-Friedman and IDTEch Ex Researchers that TPU can pose a problem.

"TPU itself is the first choice of encapsulate but not likely to be the last. This is because it is not the most stretchable thus restricting the clothing-like feeling of e-textiles particularly if large areas are covered. Already companies are experimenting with other material systems ..."  iD Tech Ex  (Source)

My teammate, Ezgi Ucar and I decided to play around with some of our ink formulas to see how they would do deposited onto a stretchy textile. The images and video below show visuals of a highly stretchable and conductive ink that we developed that can be deposited directly onto lycra fabric. We have a lot of work to do to get something like this ready for mass production, but experimenting with what's possible is key to crafting good solutions.