SoilTile turns Earth into an oversized touchpad

We’re used to interacting with electronic technology that is cold, rigid, and overwhelmingly artificial. The device you’re reading this on doesn’t resemble anything found in nature and, consciously or not, you see it as something separate from the natural world. But what if the dividing boundary was less distinct? How would that affect the way you interact with technology? An international team of engineers and scientists created a sensor system called SoilTile that can help answer those questions.

SoilTile is a system for turning patches of ground (dirt, grass, moss, sand, etc.) into arrays of pressure sensors. Imagine something like a Dance Dance Revolution pad, but with a grassy surface instead of plastic and the ability to detect varying degrees of pressure. SoilTile could be useful for presence detection or even direct interaction with electronic systems. One could, for instance, open a patio door by simply walking across the lawn.

This works in a manner similar to conventional pressure-sensing mats, with cathodes and anodes separated by a compressible medium. In this case, that medium is soil. The top “cover” can be anything from real grass turf to a comfy toe-pleasing shag rug. The prototype SoilTile has four cathodes to create a 2×2 grid of pressure sensors and several tiles can be positioned adjacent to each other to produce larger arrays. 

An Arduino Mega 2560 board monitors the cathodes through analog pins and their reported voltages correspond to pressure. When weight increases on a cathode, it compresses the underlying soil and gets closer to the anode. That lowers resistance and increases voltage. It isn’t precise or accurate, but it is good enough for a wide range of applications.

Best of all, all of the material is recyclable, reusable, or compostable. That makes SoilTile particularly suitable for temporary installations, such as at outdoor events.

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