Print Email Facebook Twitter An Edible Humidity Indicator That Responds to Changes in Humidity Mechanically Title An Edible Humidity Indicator That Responds to Changes in Humidity Mechanically Author Zhang, M. (TU Delft Complex Fluid Processing) Arunachalam, Abinaya (Rijksuniversiteit Groningen) Perrin, H.R.L. (TU Delft Complex Fluid Processing) Polat, S. (TU Delft Complex Fluid Processing; Marmara University) Groenewold, Jan (Universiteit Utrecht; South China Normal University) Mendes, E. (TU Delft ChemE/Advanced Soft Matter) Eral, H.B. (TU Delft Complex Fluid Processing; Utrecht University) Date 2023 Abstract Elevated humidity levels in medical, food, and pharmaceutical products may reduce the products' shelf life, trigger bacterial growth, and even lead to complete spoilage. In this study, we report a humidity indicator that mechanically bends and rolls itself irreversibly upon exposure to high humidity conditions. The indicator is made of two food-grade polymer films with distinct ratios of a milk protein, casein, and a plasticizer, glycerol, that are physically attached to each other. Based on the thermogravimetric analysis and microstructural characterization, we hypothesize that the bending mechanism is a result of hygroscopic swelling and consequent counter diffusion of water and glycerol. Guided by this mechanism, we demonstrate that the rolling behavior, including response time and final curvature, can be tuned by the geometric dimensions of the indicator. As the proposed indicator is made of food-grade ingredients, it can be placed directly in contact with perishable products to report exposure to undesirable humidity inside the package, without the risk of contaminating the product or causing oral toxicity in case of accidental digestion, features that commercial inedible electronic and chemo-chromatic sensors cannot provide presently. Subject Best-by dateCaseinate filmEdibleHumidity indicatorIntelligent tagMechanical bendingRolling To reference this document use: http://resolver.tudelft.nl/uuid:9dd47dcd-30b2-475a-9e16-098de2b826c2 DOI https://doi.org/10.1021/acsapm.3c00344 Source ACS Applied Polymer Materials, 5 (7), 4780-4788 Part of collection Institutional Repository Document type journal article Rights © 2023 M. Zhang, Abinaya Arunachalam, H.R.L. Perrin, S. Polat, Jan Groenewold, E. Mendes, H.B. Eral Files PDF acsapm.3c00344.pdf 5.1 MB Close viewer /islandora/object/uuid:9dd47dcd-30b2-475a-9e16-098de2b826c2/datastream/OBJ/view