Well, noises anyway. [Dmitry Morozov] and [Alexandra Gavrilova] present an interesting electronics-based art installation, which probes a large chunk of crystalline magnetite, using a pair of servo-mounted probes, ‘measuring’ the surface conductivity and generating some sound and visuals.
It appears to have only one degree of freedom per probe, so we’re not so sure all that much of the surface gets probed per run, but however it works it produces some interesting, almost random results. The premise is that the point-to-point surface resistivity is unpredictable due to the chaotically formed crystals all jumbled up, but somehow uses these measured data to generate some waveshapes vaguely reminiscent of the resistivity profile of the sample, the output of which is then fed into a sound synthesis application and pumped out of a speaker. It certainly looks fun.
From a constructional perspective, hardware is based around a LattePanda fed samples by an ADS1115 ADC, which presumably is also responsible for driving the LCD monitor and the sound system. An Arduino is also wedged in there perhaps for servo-driving duty, maybe also as part of the signal chain from the probes, but that is just a guess on our part. The software uses the VVVV (Visual Live-programming suite) and the Pure Data environment.
Modern technology is riddled with innovations that were initially inspired by the natural world. Velcro, bullet trains, airplanes, solar panels, and many other technologies took inspiration from nature to become what they are today. While some of these examples might seem like obvious places to look, scientists are peering into more unconventional locations for this transistor design which is both inspired by and made out of wood.
The first obvious hurdle to overcome with any electronics made out of wood is that wood isn’t particularly conductive, but then again a block of silicon needs some work before it reliably conducts electricity too. First, the lignin is removed from the wood by dissolving it in acetate, leaving behind mostly the cellulose structure. Then a conductive polymer is added to create a lattice structure of sorts using the wood cellulose as the structure. Within this structure, transistors can be constructed that function mostly the same as a conventional transistor might.
It might seem counterintuitive to use wood to build electronics like transistors, but this method might offer a number of advantages including sustainability, lower cost, recyclability, and physical flexibility. Wood can be worked in a number of ways once the lignin is removed, most notably when making paper, but removing the lignin can also make the wood relatively transparent as well which has a number of other potential uses.
If you can’t answer the riddle, don’t feel bad. Metal conductors usually conduct electricity and heat. Usually, that’s true, but researchers at the Department of Energy’s Lawrence Berkeley National Laboratory and at the University of California, Berkeley, have found that vanadium dioxide can conduct electricity without conducting heat.
The Wiedemann-Franz Law states that good conductors of electricity are also good conductors of heat. Vanadium dioxide not only switches from an insulator to a conductor at 67C (152F), but it appears that it also doesn’t conduct as much heat as that law predicts while it is in its electrically conductive phase.
[Ryan] designed a PCB that lets you easily take readings from a commercial electrical conductivity probe over I2C. Conductivity measurements are great for measuring the salinity of a solution, which is useful for applications like hydroponics. While the probes themselves are a bit pricey (on the order of $50 from eBay), they are very accurate and last a long time.
Commercial conductivity probes contain platinum electrodes to prevent corrosion. The electrodes are excited with an AC signal, which prevents polarization of the solution and avoids chemical reactions at the electrodes. The voltage across the two electrodes is measured while the electrodes are being excited, which is proportional to the conductivity of the solution
[Ryan]’s board generates +/-5v and uses a Wien bridge oscillator to generate a sine wave which excites the outermost electrodes. The voltage across the electrodes is amplified and fed into a MCP3221, an inexpensive 12-bit ADC with an I2C interface. [Ryan] also wrote an Arduino library for the MCP3221 so you can easily get your probe up and running.
Hardware modding can take you to some strange places: sometimes, you think of really useful improvements to your most practical devices. Other times, you turn a cup of tea into a theremin. This is true at least for [Kyle McDonald], who immersed the L/R leads of an 1/8″ cable in a cup of tea, and connected it to a computer running Max/MSP with a special patch. The result is a working, miniature theremin you can drink after you’re done playing. This process should work with any liquid, so feel free to use beer, cola, water, or anything you think will taste better after you’ve run a small charge through it.