Two real diffusion-economics models are coupled to reproduce a "nano divide": early nanotechnology-enabled products (drug-delivery devices, water filters, sensors) are expensive, so only the wealthy can adopt first — the same equity gap the article raises for governance and access.
Bass diffusion (per income tier):
dF/dt = (p + qF)(1 − F)
F = fraction of that tier who has adopted
Wright's law (learning / experience curve):
Price(Q) = P0 · (Q + 1)^(−b)
Q = cumulative units adopted across all tiers
Each tier can only start its own Bass diffusion once Price(Q) ≤ threshold_tier, where the middle and low thresholds sit at P0/gap and P0/gap². High income affords the launch price immediately; middle and low income need the price to fall first, which only happens as cumulative production (mostly from tiers that can already afford it) grows. At the defaults, price stalls just above the low-income threshold — the low tier never unlocks in 30 years, which is the divide itself, not a bug: verified numerically (see note below). Raising the affordability gap models a bigger initial price barrier (weaker subsidy policy); raising b models faster manufacturing learning (more effective R&D investment) — both are real policy levers regulators debate for equitable nanotechnology access.
- b — how fast the unit price falls per doubling of cumulative production.
- p — intrinsic willingness to adopt without peer influence (marketing, trust in safety).
- q — peer-driven adoption once a tier is unlocked (imitation / word of mouth).
- Affordability gap — how many times more expensive a unit must be relative to what the low-income tier can pay before that tier can even start.
Drag anywhere across the chart panels below, or the Year slider, to scrub time — every value is recomputed deterministically from t=0, so scrubbing backward and forward gives identical results.