Cells are seeded at random pore sites across a spherical porous scaffold. Each cell's fate is set by the worse of two independent factors: connectivity — how many live neighbor cells sit close enough to physically contact and signal it — and oxygen — how much dissolved O₂ survives diffusing inward from the surface after being consumed by every cell layer along the way.
health → min(connectivity, oxygen)
O2(depth) = exp(−k · density · depth)
- Too sparse — oxygen reaches everywhere fine, but cells sit too far apart to form the neighbor contacts needed for coordinated organization; they wither in isolation (amber).
- Too dense — plenty of neighbors, but the thick outer cell layer consumes oxygen faster than it can diffuse inward; the surface thrives while the core starves into a necrotic center (dark red).
- Sweet spot — dense enough for signaling, sparse enough for oxygen to reach the core: uniform, healthy tissue throughout (green).