Fig. 4: Flexible time–temperature indicator on paper substrate during operation. | Nature Communications

Fig. 4: Flexible time–temperature indicator on paper substrate during operation.

From: Intelligent non-colorimetric indicators for the perishable supply chain by non-wovens with photo-programmed thermal response

Fig. 4

a, b Photographs of two differently programmed indicators while working at 35 °C with different response timescales: a minutes (device first photo-programming dose = 72 mJ/cm2) and b hours (first photo-programming dose = 80 mJ/cm2), captured at different observation times. (Scale bar: 5 mm). c, d Operation during sunlight-induced warming. Exemplary goods (milk, drugs) are exposed to sunlight for 30 min. The temperature of each item, measured by a thermocouple, is displayed in the red box. The photographs also show the corresponding visual response of non-wovens, encapsulated by yellow plastic sheets to screen UV radiation and prevent undesired residual crosslinking (c, top-right inset, scale bars, 5 mm). In the top-right inset in (c), arrows highlight the flexible and robust multilayer interface at the device edge. Bottom-right insets: magnified view of the indicator on the drug blister, before (c) and after (d) sunlight warming.

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