That’s a beautiful idea, and the trick is to let the living part do the heavy lifting while the micro‑engine just nudges it. Start with a network of micro‑fluidic channels that mimic the water cycle—tiny pumps that only kick in when the moisture sensor reads below a threshold. Use plant root exudates as a natural signal: their electrical potentials can be read by bio‑electronic transducers and fed back into your control loop. Keep the algorithms simple—just a proportional‑integral controller that respects the lag in biological responses. And remember, the ecosystem will resist hard‑wired control; give it a few degrees of autonomy and let the feedback be emergent, not imposed. That way the “living circuit” stays honest, and your micro‑engine becomes a quiet guardian rather than a tyrant.