Fluidics is the construction of computing systems using fluids.
They employed water or air in plastic channels to implement logic gates; the gates were interconnected by standard, flexible plastic tubing. The advantage was their noise immunity, but their size and physical awkwardness was among their many negatives. A typical four-input AND or OR gate alone was about half the size of a deck of cards.
Paper microfluidics don’t require external pumps or power sources, they can be small, portable, disposable, easy to distribute and operate, low-cost, technically simple to make, and they only need tiny amounts of sample fluid. A minimal setup can be as simple as heating the lines drawn by wax crayon on extra absorbent paper, like cellulose paper and using droplets with food colouring.