Temperature Responsive Smart Photonic Polymers for Printable Autonomous Sensors

An efficient approach to reduce food waste is the incorporation of smart temperature sensors to individual products, providing visual feedback that shows if the consumable has been exposed to jeopardous temperatures. With a tunable temperature response frame, these labels also allow for easy monitoring of transport conditions of medicines and other consumables or industrial/healthcare processes such as steam sterilization.<br/>Recently we have fabricated colored photonic polymers as smart temperature sensors. Two different approaches of incorporating temperature response in these coatings have been developed using a printable fabrication method, showing battery free and user-friendly properties.<br/>By using shape memory photonic polymer coatings, we demonstrate that it is possible to program various optical and temperature responses through embossing the surface with microsized topographies that cause light scattering, making the coating appear opaque and colorless. The temperature response can further be programmed through the fabrication method by adapting the polymerization intensity. The simple procedure of activating this surface scattering that camouflages the printed features of the coating allows for the activation of time temperature tracking of individual products down the chain from retailer to consumer.<br/>A different mechanism for printable time-temperature sensors is based on the order loss of the self-organizing liquid crystal coating which leads to loss of reflected color. A time-temperature dependent loss of color is achieved by making use of supramolecular dynamic interaction freedom for applications that require high temperature monitoring such as steam sterilization verification. A coating in which acid-functionalized groups provide physical interactions without any covalent crosslinks is prone to gradually lose the color reflection when exposed to temperatures that grant for enough freedom through the dynamic H-bond monomer-dimer equilibrium shift. Furthermore, this system is sensitive to humidity due to the interaction between water and the dynamic H-bonds, as a result an even higher scattering state is obtained due to the increased surface roughness due to the surface interaction with water.<br/>Current research focusses on controlling the temperature scope and response type of these order loss coatings with the aim to achieve the ability to program a specific response tailored for the application between 15 and 120°C.