Abstract
Spoiled perishable products, such as food and drugs exposed to inappropriate temperature, cause million illnesses every year. Risks range from intoxication due to pathogen-contaminated edibles, to suboptimal potency of temperature-sensitive vaccines. High-performance and low-cost indicators are needed, based on conformable materials whose properties change continuously and irreversibly depending on the experienced time-temperature profile. However, these systems can be limited by unclear reading, especially for colour-blind people, and are often difficult to be encoded with a tailored response to detect excess temperature over varying temporal profiles. Here we report on optically-programmed, non-colorimetric indicators based on nano-textured non-wovens encoded by their cross-linking degree. This combination allows a desired time-temperature response to be achieved, to address different perishable products. The devices operate by visual contrast with ambient light, which is explained by backscattering calculations for the complex fibrous material. Optical nanomaterials with photo-encoded thermal properties might establish new design rules for intelligent labels.
Highlights
Spoiled perishable products, such as food and drugs exposed to inappropriate temperature, cause million illnesses every year
Stability tests allowing such data to be determined are based on the use of controlled temperatures, which is generally different from the real life, during which undesired temperature variations can occur by an enormous variety of issues during transportation, distribution, and storage
Indicator materials are generally highly difficult or impossible to be programmed, i.e. to be encoded with a tailored response of their components in order to detect excess temperature over varying temporal profiles, ranging from a few minutes up to several days to address the need of many different classes of perishable products
Summary
Spoiled perishable products, such as food and drugs exposed to inappropriate temperature, cause million illnesses every year. Electronics embedding radio-frequency identification tags and wireless antennas, whose resonant response evolves while they are conformed to spoiling food surfaces[10], are elegant data loggers capable of transmitting quality information, but intelligent indicators providing a clear and userfriendly visual information of the overall time–temperature history of an item have the potential to induce a much better perception in consumers[7], greatly improving general safety without affecting electronic waste To this aim, an indicator must be based on a material showing a continuous and irreversible change of a physico-chemical property depending on the time–temperature profile undergone by the product with which it is coupled. A twolevel information is incorporated in the devices by controlling the degree of cross-linking in organic fibers by initial system encoding through calibrated photo-exposure doses (which allows a desired time–temperature profile response to be achieved) and embedding readable patterns that emerge along with temperature exposure in a continuous way (which enables the device to operate by visual contrast with ambient light, in a highly userfriendly way)
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