Silver nanoparticles (AgNPs) grafted onto a textile fiber dissolve continuously, releasing bactericidal Ag+ ions. Release follows a simplified Noyes–Whitney dissolution law:
dM/dt = -k · A · f_res
C(x,z,t): ∂C/∂t = D∇²C + Σ source(x,z) − boundary loss
This is a genuinely 2D field — the fiber runs along x, ions spread through the moisture film in the (x,z) plane. Released ions are solved here on a 48×24 grid with explicit finite differences (open/absorbing edges model ions carried away from the fabric). Drag the field to pan, scroll/pinch to zoom into the concentration pattern around the fiber.
Bacteria die according to a Hill-function dose–response, the standard pharmacodynamic model for antimicrobial killing:
kill_rate(C) = k_max · C² / (C² + MIC²)
MIC is the minimum inhibitory concentration — a more resistant strain needs a higher local [Ag+] before the kill rate becomes significant. Where concentration stays well below half the MIC, surviving bacteria divide logistically and repopulate empty slots.
- Release rate k — the intrinsic AgNP dissolution rate constant; higher k means faster ion release per unit reservoir remaining.
- Diffusion coefficient D — set by fabric moisture; higher D spreads ions faster but also dilutes and clears them faster past the absorbing edges.
- MIC slider — bacterial resistance; a higher value needs more silver to achieve the same kill rate.
- Max kill rate / regrowth rate — the Hill ceiling and logistic division constant; tune these to see how aggressive killing trades off against a strain's ability to bounce back.
- Wash cycle — real antibacterial textiles lose efficacy after repeated laundering as surface-bound AgNPs are mechanically stripped; each click cuts the remaining silver reservoir by 30%.