Left: Schematics of conductive circuits printing on the leaf surface. A microfluidic chip is placed on top of the leaf abaxial surface and clamped in between two holders. The inset shows a schematic layout of a printed microsensor with two contact pads and a stripe going across a single stoma. The conductive stripe breaks when stoma opens, increasing sensor resistance. Right: Pictures of a stoma wiring on Spathiphyllum wallisii. Copper tape is placed directly onto the abaxial leaf surface with a printed ink, and the wired stoma is connected to a multimeter.