In non-recirculating hydroponic systems, we want to fill containers with nutrient rich water let's say up to an inch, let the plants take up the water , give the plants some air time for a few hours, and then restart a filling cycle.
I was thinking a sponge could be used as a sensor and actuator. The sponge valve would be dry and open. As the water reached an inch the sponge would get wet and expand in a cylinder and push something that blocks the flow of water in a 4mm irrigation tube. As the water gets absorbed by the plants, the sponge would dry out and the pressure lowers and eventually it becomes low enough that the water starts flowing again, for a new cycle.
Is a cellulose sponge realistic for this. In particular would the wetting and drying state of the sponge be sufficiently stable or would it rapidly deteriorate? Is there another material that would be better suited?