I experimented with the notion of being able to generate 3d scans of objects based on their electrical resistance. This came out of the work I did on my water keyboard that was controlled by locating your hand in a trough of water. Aside from being able to simply create a novel 3d imaging system I was more interested in the potential to “perceive” objects based on their electrical characteristics. Heat mapping low resistance parts (even interiors) of a scanned object or naturally distorting the apparent physical shape based on resistance would allow for some artistic renderings at the very least. I liked to think about it as “how would you see this object if you could sense resistance”.
A related field of remote sensing in this vein already exists that I was able to reference.
Electrical resistivity tomography – Wikipedia
Electrical resistivity tomography (ERT) or electrical resistivity imaging (ERI) is a geophysical technique for imaging sub-surface structures from electrical resistivity measurements made at the surface, or by electrodes in one or more boreholes. If the electrodes are suspended in the boreholes, deeper sections can be investigated. It is closely related to the medical imaging technique electrical impedance tomography (EIT), and mathematically is the same inverse problem. In contrast to medical EIT however ERT is essentially a direct current method.
Ultimately I produced two versions of the machine. First was a hollow sphere with electrodes placed longitudinally. This sphere was suspended on a servo that rotated around the object being scanned at its center while the whole scanning array was submersed in solution. Results were inconsistent. I attributed this to several factors and ended up building a second device with a more simplistic scanning chamber and controlled array setup so that I could better isolate and resolve the problems. Ultimately this second array also was also too erratic to produce viable results despite heavy experimentation.
I constructed the entire device from milling the graphite electrodes to designing and building the electronics to perform the scan and interface USB with my computer. I also developed the microprocessor code and .NET 3d rendering software to interpret the results and plot them in a 3d space in which you could zoom, rotate and cycle through readings.
Ultimately the resistive effect of the scanned object was so minor as to be effectively masked by the inherent noise and limits of measurement accuracy of the design; in concept this is still a viable scanner but I am disappointed to have come up short on this prototype. I did learn a lot in the process, discovered a model to better describe the nature of how electrical current flows through a liquid, and solved a series of very challenging electronic problems.
