Color-changing material shows when medications get too warm

Date:
May 31, 2023
Source:
American Chemical Society
Summary:
Some foods and medicines, such as many COVID-19 vaccines, must be
kept cold. As a step toward a robust, stable technique that could
indicate when these products exceed safe limits, researchers report
a class of brilliantly colored microcrystals in materials that
become colorless over a wide range of temperatures and response
times. As a proof of concept, the team packaged the color-changing
materials into a vial lid and QR code.


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FULL STORY ==========================================================================
Some foods and medicines, such as many COVID-19 vaccines, must be kept
cold. As a step toward a robust, stable technique that could indicate
when these products exceed safe limits, researchers in ACS Nano report
a class of brilliantly colored microcrystals in materials that become
colorless over a wide range of temperatures and response times. As a
proof of concept, the team packaged the color-changing materials into
a vial lid and QR code.

Walk-in freezers and refrigerated trucks generally maintain their set temperatures, but accidents can happen. Wireless sensors can monitor the temperature of individual products, but these devices produce a lot of electronic waste. Recently, researchers have suggested using materials
that act as visual indicators to provide this information with less
waste. Yet some current options using colorful reactions or dyes produce
hues that can fade. Or they only track above-freezing temperatures, which
isn't useful for some COVID- 19 vaccines that can actually start breaking
down below freezing -- above -4 or -94 degrees Fahrenheit. So, Yadong
Yin, Xuemin Du and colleagues wanted to develop a better color-changing material with tunable melting to track a wide range of temperatures.

The researchers used structural colors, instead of dyes, for their
indicator system. The team made glycerol-coated silicon dioxide
nanoparticles, which appeared bright green or red when they clustered
together into microcrystals in water. Next, they created liquids with
variable melting points by mixing different proportions of polyethylene
glycol or ethylene glycol and water. When these two parts were put
together, they could produce an irreversible color loss when the temperature-triggered solution melted and the microcrystals broke
apart. The materials could be customized to track temperature exposures
from - 94 to +99 degrees Fahrenheit that lasted from a few minutes to
multiple days.

In other experiments, the two-part indicator systems were packaged
into flexible round vial labels and a QR code. These systems were very sensitive and successfully indicated when the materials got too warm. The researchers say that structural color-changing materials hold promise
for the diverse scenarios encountered in medical cold supply chains.

The authors acknowledge funding from the National Natural Science
Foundation of China, the National Key R&D Program of China, the Youth Innovation Promotion Association of Chinese Academy of Sciences, the
Guangdong Regional Joint Fund- Key Project, the Chinese Academy of
Sciences Key Laboratory of Health Informatics, the Shenzhen Institutes
of Advanced Technology and the Fundamental Research Program of Shenzhen.

* RELATED_TOPICS
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========================================================================== Story Source: Materials provided by American_Chemical_Society. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Chao Huang, Yuanyuan Shang, Jiachuan Hua, Yadong Yin, and Xuemin Du.

Self-Destructive Structural Color Liquids for Time-Temperature
Indicating. ACS Nano, 2023 DOI: 10.1021/acsnano.3c00467 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/05/230531101950.htm

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