Abstract: We describe various methods for making preprogrammed logic systems using knotted yarns. We show that the topology of the knots controls the mixing ratio of the reagents coming into the knots, and thus the ratio can be adjusted by choosing a specific knot. A serial dilutor is built by knotting multiple yarns into a web of well defined dimension. In addition stretchable yarn can be used to control the capillary pressure and hence the flow rate of the liquid, by pulling the yarn. Furthermore, we demonstrate the possibility of patterning impermeable/hydrophobic regions in to the yarn. Finally, we propose that biodegradable yarns can be used into these platforms to build various multi/single cellular scaffolds.