PVC Wearables

Master of Interaction Design - Institue of Advanced Architecture of Catalonia - 2013

This is a small post that tells the story of making pvc garments for RF sensors. PVC sheet are awesome. Flexible. Strong. Semitransparent, and cheap. Ideally, we are not supposed to laser cut them, but because fablabBCN is awesome, so we can. Set the power to (15~20) and the speed to 75 on the Epilog laser and go ahead. It should be fast and not so powerful otherwise the sheets are deformed or become very curled that you can’t work with them.

Those wearables’ shapes are inspired by plane surfaces generated from volumes created by antenna fields. Well, the field shapes change according to antenna design and frequency, but those prototypes are only inspired, it is not accurate or parametric, which is something that could be investigated in a further iteration. Below is a step by step documentation on how the process takes place and how the material looks like through the different phases. The idea, initially was to make use of how interestingly the material diffuses the light, and use it to reflect the sensor readings, but the plan didn’t run exactly as imagined, at least, so far.

Now, lets see, how to integrate the sensor within. In the early stages of this project, I had trials for finding ways to make the lightest circuit possible, I tried conductive ink (which was incredibly impossible with smd components) and tried copper sheets, which was fine for most components, except for the very small RF log piece.

It gets really challenging trying to be creative while using smd components!

So finally I gave up and decided to just mill a normal pcb board because the above ones didn’t work!

Then trying to go creative with the antenna, that was even more challenging: For instance,this is a pcb milled fractal antenna, that didn’t mill correctly.

Weaved wires are incredibly attractive to work with..but performance wise they don't work. Then I got more crazy and tried, weaving conductive wires in fractal shapes, but that was completely insane.

The conductive copper sticker on cardboard wasn't a bad trial, but still the antenna alignment was an issue. So I just used normal 1.5mm laminated copper wire loop and biquad antennas, and they worked. It is challenging to combine creative crafting with antenna that needs considerations with orientations, ground connections, alignment..etc. I used online javascript calculators to get dimensions and specifications. So initially the circuit was that big:

Then replacing Arduino with ATTiny84, such as the one below:

then we end up with a much accomodated circuit:

which is rough on a prefboard, yet it works, just plug in 2 CR2032 3V batteries. I made a necklace that goes with the pvc piece above, the integration isn’t great, but ..even Raquel likes it!

The good things is that it works nicely with measurements,as illustrated in the video below, it just deserves a second chance for fabrication and integration.