Color-Changing Material Indicates Temperature of Medicines

Color-Changing Material Indicates Temperature of Medications It is a known fact that many vaccines, food products and pharmaceuticals must be protected under cold storage conditions. Researchers at ACS Nano have taken a new step toward a robust and stable technique that could demonstrate when these products exceed safe limits, revealing the presence of a class of bright-colored microcrystals in materials that become colorless across a wide temperature and reaction time range. As a proof of concept, the team packaged color-changing materials into a bottle cap and a QR code. Embedded freezers and refrigerated trucks generally maintain their set temperatures, but unexpected situations can occur. Wireless sensors can monitor the temperature of individual products, but these devices generate excessive electronic waste. Recently, researchers have suggested using materials that serve as visual indicators to provide this information with less waste. However, some existing options using colored reactions or dyes produce shades that fade over time or only track temperatures above the freezing point; this is not useful for some COVID-19 vaccines that can begin to deteriorate below the freezing point (above -4° or -94° Fahrenheit). For this reason, Yadong Yin, Xuemin Du and colleagues wanted to develop a better color-changing material with adjustable melting points to monitor a wide temperature range. The researchers used structural colors instead of dyes for the indicator systems. The team produced silicon dioxide nanoparticles coated with glycerol that appeared bright green or red when clustered as microcrystals in water. They then created liquids with variable melting points by mixing polyethylene glycol or ethylene glycol and water in different proportions. When these two components were brought together, an irreversible color loss could occur when the temperature-triggered solution melted and the microcrystals dispersed. The materials could be customized to track temperature exposures between -94° and +99° Fahrenheit lasting from several minutes to several days. In other experiments, two-part indicator systems were packaged as flexible round bottle labels and a QR code. These systems were highly sensitive and successfully showed when materials became too warm. The researchers note that structural color-changing materials show promise for various scenarios encountered in medical cold supply chains. Academic Reference: Chao Huang et al, Self-Destructive Structural Color Liquids for Time-Temperature Indicating, ACS Nano (2023). DOI:10.1021/acsnano.3c00467. pubs.acs.org/doi/10.1021/acsnano.3c00467 Source