But there are already a hundred different methods for doing this. Saltwater batteries, the type that power emergency lights in life rafts, activate upon contac

But there are already a hundred different methods for doing this. Saltwater batteries, the type that power emergency lights in life rafts, activate upon contact with water. You just need any two dry electrodes that, when in contact with not-pure water, result in a current. I'm not sure that the novelty of making them out of ink would change things. https://en.wikipedia.org/wiki/Water-activated_battery https://en.wikipedia.org/wiki/Water-activated_battery