Flexible time-temperature indicator: a versatile platform for laminated paper-based analytical devices

摘要

Time-temperature indicators are devices employed for monitoring thermal history of perishable food products from storage to consumption. As the food industry has opted for intelligent packaging, which also involves thin foldable wrappings, a requirement arises for a flexible device capable of attaching and sensing on a curved product surface. In this study, we have fabricated a distance-based flexible time-temperature indicator (FTTI) by employing electronic cutting machine and through press lamination of thermoplastic films; we have incorporated the FTTI with a unique starting actuation switch made of thin (150 mu m) cover glass. Flow profile in 0.45 mu m nitrocellulose membrane is measured for oleic, octanoic, and decanoic acids representing test temperatures of 5, 15 and 30 degrees C, respectively. Results demonstrate the sensor to be robust and flexible with precise responsiveness to oscillating temperature conditions. Further improvement in timescale is achieved by employing a series of fan-shaped cut channels. This two-dimensional flow increases the device time by 170% in comparison with straight channel and improves scale readability by achieving a linear distancetime relation in the porous membrane. The advantages of low cost, simple design, freedom from equipment, robustness, and flexibility render the FTTI a versatile platform for distance-based diagnostics, food quality control, and environmental monitoring devices.