A Passive Time–Temperature Witness Label for Cold-Chain Shipment

Design paper (SIMULATED, NOT MEASURED) for a passive, no-electronics adhesive time-temperature witness label for food and vaccine cartons. A hexanoic-octanoic fatty-acid eutectic phase-change plug with 8.0 C melting onset feeds a 60.0 mm printed capillary track; the melt-front position integrates Arrhenius-weighted thermal exposure above threshold. Computed front rates, three 48 h worked shipment profiles, read resolution, and activation-energy mismatch against representative food-spoilage and vaccine-degradation values are reported from the accompanying computation script. No device has been built or tested in hardware.