Surface Activation Lab: Dose, Wetting & the Aging Clock

Give the polymer a plasma dose and watch the water droplet respond — then let the treated surface sit, and watch some of the gain quietly slip away.

Schematic teaching model. The droplet spreads at constant cross-section (volume-conserving circular cap) as the contact angle falls; polar-group density, the dose–angle curve, and the aging clock follow the qualitative trends of oxygen-plasma polymer activation (surface-energy rise per Young / Owens–Wendt thinking, partial hydrophobic recovery as chains reorient) — numbers are illustrative, not calibrated to any one polymer.