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PolySense

Augmenting materials with electrical properties ⚡⚗️

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CUSTOM SENSORS!
Made out of anything fibrous / porous! (by "augmenting" materials)

Pressure, stretch, capacitive touch, humidity, or temperature sensing?
We got you covered.

LINKS SHORTCUTS!

💥 NEWS! 💥 

1) 🎓 RESEARCH

2) 💀 HACK A DAY ARTICLE

3) 🤖 MAKER FAIRE

4) ⚡ ARS ELECTRONICA
📜 PROJECT LOGS📜

1) 🔬 REVERSE ENGINEERING

2) 🥽 HCI EXPLORATION

3) ✨ ART INSTALLATIONS

4) 🔥 HEATING + SENSING

Application examples

Artistic visualizations:  

VR gloves:

CCC leggings:


What!?


We use a chemical process called in-situ polymerization (explained later).

It allows functionalizing almost anything fibrous and porous materials (natural ones like cotton or cork work better than synthetics in general).

Once polymerized, your originally non-functional material ends up with sensing capabilities:
- pressure 
- stretch
- capacitive
- humidity
- temperature (bonus: heating is also possible)


Why!?


In our hackerspaces and research labs, we explored musical textile interfaces and we used a commercial piezo-resistive material (pressure sensitive).

The only good one was expensive and became hard to get because of a new exclusive contract with another company.

So with material scientists, we reverse-engineered it, and made a DIY process simple enough for the kitchen of our hackerspaces.

Illustration of the piezo-resistive effect:


How?

The following video summarizes the process, but you'll need chemical products:
- Europe source: Pyrrole + Iron Chloride
- US source: Pyrrole + Iron Chloride

...and get a machine to mix your materials for about 1h, example:
- chemistry magnetic stirrer
- ice cream maker
- a batter mixer
- a camping washing machine
- or you can build it with a drill and a bucket for example.


Protocol summary

(adapt X to your quantity):

1) Water: ( X ) ml - fill the container so that there's about 75% of textile (but don't put it yet!)

2) Pyrrole: ( X / 250 ) ml - add it and stir it

3) Material: add it and keep stirring for 10 minutes

4) Iron chloride: ( X / 100 ) mg - keep stirring for 30-60 minutes depending on the material

5) for capacitive sensors: you can repeat this procedure, or multiply these proportions and polymerization time by 2 to 5 (depending on the material too).

💡💡💡💡💡💡💡💡💡💡💡💡💡💡

The process, called in-situ polymerization, is particularly unique because:

- First we soak the textile with the monomer (steps 1 to 3)
- Then we trigger the polymerization (in-situ, or in place)

This reaction creates "a kind of molecular dyeing with carbon" which has much stronger properties than a coating approach.

💡💡💡💡💡💡💡💡💡💡💡💡💡💡

Sourcing the products

The chemical products were ordered from 2 possible sources:

- Europe:
https://www.glentham.com/en/products/product/GK9750
https://www.glentham.com/en/products/product/GK2873

- US:
http://fishersci.com/shop/products/pyrrole-tci-america-3/P057425ML
http://fishersci.com/shop/products/iron-iii-chloride-hexahydrate-99-analysis-acros-organics-3/AC217091000

Note: every material reacts differently so you'll have to do a couple of tests to get the right chemistry ratios, and the right timings...

Detailed presentation:

  • Heat Generation + Sensing

    Drix02/12/2020 at 12:17 0 comments

    Heat Generation

    We polymerized a glove, and looked if we could warm it with a bit of power, it's quite nice in winter!

    With about 0.6A x 20V = 12W (yeah, not exactly low-power), the glove went from 20°C to 53°C (= from 68°F to 127°F) in about 9 seconds (it's not very comfortable above that temperature).

    For scientific reasons, we waited until the magic blue smoke came, and it was 130°C (266°F), wait for it:


    Heat Sensing

    Of course, we don't want to burn people so we looked if we could measure the resistance variation with heat. 

    The measures are fairly inaccurate as we used a thermal camera, but the graph below gives an idea of how this Resistance VS Temperature behaves:

    If we can ensure that there is no humidity (sweat, rain, etc), it seems realistic to use the resistance measures to estimate the temperature and stop heating above a threshold (ex: 74 ohms <=> 50°C / 122°F).

  • Artistic applications

    Drix02/12/2020 at 00:54 0 comments

    A couple of artistic projects were already born out of the PolySense technique:

    - - -

    Stymphalian Birds

    http://AudreyBriot.fr/stymphalian-birds/

    Stymphalian Birds is an art installation exploring the aesthetics of a hybrid textile at the crossroads of electronics and haute couture. The textile combines traditional hand-crafted elements with digital technology, biological artefacts, and chemistry.


    Stymphalian Birds are situated at the intersection between traditional featherwork and material science, the resulting textile offers complex haptic interactions with feathers.

    - - -

    Digital Topography

    This work is already exhibited in a french museum, but the video is still in progress.

    This gif illustrates the interaction:

    ...and in this video made in our hackerspace (datapaulette.org), we show the 1st test with capacitive sensing on our own polymerized pleated fabric:

  • Explorations

    Drix02/11/2020 at 03:13 0 comments

    Machines

    We started with chemistry magnetic stirrers, but we needed bigger, so we built our own gig with a drill (left). We then tried polymerizing a pre-stretched material to see if it would help (right), but the results were not particularly convincing...


    Augmenting existing materials

    Zipper

    This is probably the simplest, but most unique to this process, we don't modify materials mechanically. This zipper used to be white, but the polymerization made it black. Here we use the constant resistance of the augmented material to measure how much the electricity has to travel depending on the closed / open state (250k => 600k). Obviously, it's a continuous measure, so this is a bit like a flexible potentiometer:

     - - -

    Kinesio tape

    This is a sticky tape that can be purchased in most pharmacies for sprain or dislocation, it's made of cotton and glue to stick to the skin. As illustrated below, it can be used as linear slider (a), pressure sensor (b), xyz touch pad (c) and stretch/flex sensor (d).

    Note: an academic paper about it was published at the Augmented Humans Conference.

     - - -

    Yarns

    As seen in the demo video, we can functionalize stretchable materials, the top pictures show the range for a simple textile elastic: from 120 Kohms to 1.2 Mohms when stretched twice.

    In the bottom picures, we can see a special thread that we polymerized: it has a copper core and a textile shield, which became piezoresistive. We can thus measure the pressure at the intersection: the resistance goes from 8 Kohms to 2 Kohms with maximum pressure.


    Masking

    We tried various ways to create controlled patterns.

    Batik, a traditional technique from Indonesia, uses war to block dyeing process, and it works well for our polymerization too (see bottom right pictures + next section). The only trick is that wax needs a bit of fat to make it crack less.

    We also used quick prototyping approaches, such as 3d printing (top pics) or hot glue (bottom) on textiles, and they both work but sometimes involve boiling to remove the mask.

    Finally, we made stencils with laser cut acrylic (top pics) and the result were fairly impressive. Depending on the textile we could make 1mm traces (with 0.1mm cut in the stencil).


    Hybrids:

    That's where it gets exciting. If you take a "classic" conductive textile made out of  silver or copper (cheaper), you can etch it with vinegar (or with the iron chloride of our process).

    You can mask it with all the techniques mentioned above, then you get a flexible PCB!

    The good news here is that you can also polymerize some parts of this flexible PCB, and get pressure sensors for example - see 'c' below. By folding it, you can measure the variable resistance between 'a' and 'b':


    Bonus

    Cheap USB microscope give pretty good images now, so we looked at what polymerized, and what didn't. In picture 'a' we can see vertical thread that stayed white, probably because it's synthetic, but also possibly because it's "masked" when this textile is not stretched.


  • Reverse Engineering

    Drix02/10/2020 at 22:59 0 comments

    Origin

    While exploring musical textile interfaces, we used the piezo-resistive material below (dark grey):

    It was expensive and became hard to get because of a new exclusive contract with another company, so with material scientists, we reverse-engineered it.


    Analysis

    First, we observed a reference sample with a classic microscope:

    💡Trick: to check if it is a classic coating (thick paint) or a more sophisticated approach (like our polymerization), the best technique is to use liquid nitrogen to freeze and break the textile. Using a knife / scissors would potentially spread the eventual coating so it would not allow seeing the real inside.


    Raman Spectroscopy

    After checking the process type, Raman Spectroscopy is quite practical to try identifying materials. Here we compared our sample with similar ones from our database.

    This magic tool shoots a laser pulsed at various frequencies and it measures the energy bounced, which allows creating a spectrogram (see bottom right).

    Note: a possibly more intuitive illustration is the acoustic property of objects around us, a phone and a mug would resonate at very different frequencies...


    Solution

    It was fortunate, but this material science team happened to know several similar processes that could do this functionalization, so after trying several we worked on simplifying the simplest:


    Bonus

    One of the tools they use looks like a nuclear weapon, it took years to build it, and it definitely does't fit in our hackerspace kitchen, but next time we have to play with it!

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Discussions

Ahmed Hefnawi (Volta) wrote 03/01/2020 at 16:53 point

It's a very exciting project especially the heat sensing and overall electric capabilities that you get out of it and I like the detailed process of reverse-engineering as well as testing that you shared, thank you :)

  Are you sure? yes | no

Drix wrote 03/01/2020 at 22:23 point

Thanks a lot for your comment!

  Are you sure? yes | no

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