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

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.”

I came to experiment with the construction of an arduino-on-wood just recently because I began to be interested in the idea of “embalming” data.  Since some years ago I’ve been exploring ways to make visible and audible the human rhythms of birth and death, and at this time I wanted to get hold of these rhythms and preserve them as “arqueological references” for the future.

I used statistical data coming from the World Census Bureau and transferred it into two microncontrollers. The first one makes an LED turn on and off at the speed of the human birth rate (4.3 per second, according to the site) while the second one turns on and off a little fan at the speed of the human death rate (1.8 deaths per second). I carved two pieces of wood and embedded the electronics in them including the already programed chips.

These two objects will remain as ‘frozen” evidences about our current expansion speed in the planet.

Some more images will be appearing in this Flickr set.

Guilherme Martins and I have been working on a sculpture composed of a series of electronic circuits mixed with paper and other materials. These objects, each equipped with a custom designed PAPERduino, will be assembled into a mobile as we explore the aesthetics of electronics. In untitled circuits each piece reacts to the others to form an exposed system in constant motion and transformation.

Researching and building these has been so much fun that we thought it would be interesting to document each of the pieces here as we move along the construction process. Shown above is untitled circuit #1, made by Guilherme, a paper circuit that generates sound in real time according to the input of six LDR sensors. The code is based on Auduino from Tinker It.

More to come soon :)