For my Physical Computing final project, I want to experiment with thermochromic inks to create a print of a tree that will appear/grow gradually as more hands, and therefore more body heat, is placed at the roots. The growth of the tree is the result of an act of collaboration by multiple persons, as the tree will only fully appear when the amount of heat transferred surpasses a certain threshold.
When a person first approaches the blank canvas, they will see only a small dot on the canvas, a seed. When a hand is placed on the seed, the Lilypad temperature sensor behind the seed will send a current through sections of the conductive thread or fabric behind the print, from bottom to top which are mapped to the amount of heat received by the sensor. Roots will appear to grow from behind the person’s hand. As more hands are placed on the roots of the tree and the more heat input the sensor receives, the conductive thread or fabric will activate the thermochromic ink in sections from the trunk to the leaves, giving the illusion that the tree is growing.
Though the concept itself is simple, I’m slowly realizing the execution of this idea is quite problematic, especially in regards to electrical control of the thermochromic ink. The heating mechanism itself will be the most time-consuming issue for me to tackle as I am looking for an effect that is very specific. I’m thinking that I will need to find something that can be controlled to emit heat slowly and gradually in specific sections to achieve the organic growth effect that I am hoping for. Another problem involves the properties of the thermochromic inks. There are typically three standard types of this ink: Low Temperature thermochromic ink (activated at 15° Celcius), Body Temperature (activated at 31° Celcius or with body heat), and High Temperature (activated at 45° Celcius, or just below the threshold of skin.) I would be using the Body Temperature activated ink for this project. Unfortunately, both Body Temperature and High Temperature inks, or any ink that is activated with heat, will only change from color to colorless with heat whereas I was hoping to find an ink that would change from colorless to brown or a dark gray. (Edit: I discovered that white to colorless ink can be custom-made, but would take a few weeks to manufacture.) To address this problem, I could begin with a solid colored canvas on which the print would fade in as white, therefore creating some sort of negative space effect, but I am not crazy about it for several reasons. First, it then begins to approach the sort of kitschiness associated with “disappearing ink” and secondly, is drastically different from the minimalistic, natural look I originally envisioned for the piece.