I choose to paint the organza bubble fabric with thermoactive ink to maintain the whole theme instead of a flat drawing

I tested heating elements in the form of wire as the previous yellow heat pads were not effective in making the bubbles change colour, the heat have to be directly against the bubble fabric.

I twisted the wires in loops and squeezed them into the bubbles so that they would directly touch the fabric.

I tested with two different types of battery. The higher powered one seems better as it triggers the colour change in an instant, which was important considering that people would not stand and wait for very long to see the colour change.

after confirming that it works with the battery, i hand sewed it with clear fishing thread.