DNA folding
We were commissioned to build an exhibit for the Royal Society Summer Festival in 2017 by Weatherall Institute of Molecular Medicine. They'd got some clear ideas about how the challenge activity they wanted to illustrate their work, and experimented with a prototype with 'chromosome' strings which participants folded to link genes (paperclips) with activation sites (more paperclips) so that the cell might be a red blood cell, a white blood cell, or might not be viable.
They came to us to build a more robust version that would be able to detect whether the correct genes were matched with the correct activators to make a viable cell. The exhibit we eventually built used magnetic clips as the genes and activators, which were attached to wires running up the inside of a rope. Each combination of magnet pairs was detected by an arduino in the base, the activation of each gene was indicated by LEDs in the base, and when all the correct genes were activated and the 'chromosome' folded back into the 'nucleus' (and closed the lid) if a viable cell was detected the base would show a celebratory light display, or if you activated the wrong ones the cell could die.