Fake Plants Need Light Too is a playful and artistic experiment that uses shape memory alloy and thermochromic pigments. The result is an empathetic fake plant that quickly springs to life in the presence of light, and swiftly withers and blackens in its absence.
Team & Support
In collaboration with Chun-Wei Lee (Royal College of Art, London) and Hazar Peker (Keio University, Tokyo)​​​​​​​
My team and I were tasked with creating a playful and surprising interaction that had to be mechanical in nature. I have long been fascinated by the seemingly magical properties of shape memory alloys - a class of materials that, when heated, will spring back to a previously 'remembered' shape. No matter how one twists, tangles, or otherwise plastically deforms these metals, they simply return to the shape that they were annealed in once heated. Shape memory alloys are also resistive, allowing one to heat them by simply running a current through them. Shape memory alloys and thermochromic pigments have a lot of synergistic potential. Thermochromic pigments change color in the presence of heat, thereby acting as a way to further use the waste heat generated by running a current through a shape memory alloy. 
The main stem of the plant comprises a nitinol wire (nickel-titanium shape memory alloy) and PTFE (teflon) . The PTFE was chosen because it was non-conductive (so it would not short circuit the nitinol) and slippery in order to allow the wire to slide over it during the transformation. The leaves of the plant are made of copper in order to maximize the conductivity of heat into the thermochromic pigment covering the device. The device is enclosed in a glass and wood bell jar.

Various tests of materials, adhesives, and coatings.

The device is controlled through an external microcontroller that detects the ambient light level in the room via a photoresistor hidden in the base of bell jar. When sufficient light is detected, the plant changes from 'dying mode'  to 'growing mode', in which the controller opens a high-current circuit through the nitinol wire in the plant's stem. This causes that plant to remember it's annealed shape and begin to heat up the thermochromic paint covering the device, resulting in the plant springing to life and turning green! The controller also displays a growing animation on the accompanying 8x8 dot-matrix display. 
When the light is turned off, the device enters 'dying mode'. A 'dying' animation is played on the dot-matrix display and the controller cuts off current to the plant. As the plant cools, the thermochromic paint changes colour causing the plant to blacken while the plant slumps to the ground under its own weight.


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