Self-Destructive Structural Color Liquids for Time–Temperature Indicating

Abstract

Vaccines are undoubtedly a powerful weapon in our fight against global pandemics, as demonstrated in the recent COVID-19 case, yet they often face significant challenges in reliable cold chain transport. Despite extensive efforts to monitor their time–temperature history, current time–temperature indicators (TTIs) suffer from limited reliability and stability, such as difficulty in avoiding human intervention, inapplicable to subzero temperatures, narrow tracking temperature ranges, or susceptibility to photobleaching. Herein, we develop a class of structural color materials that harnesses dual merits of fluidic nature and structural color, enabling thermal-triggered visible color destruction based on triggering agent-diffusion-induced irreversible disassembly of liquid colloidal photonic crystals for indicating the time–temperature history of the cold chain transport. These self-destructive structural color liquids (SCLs) exhibit inherent irreversibility, superior sensitivity, tunable self-destructive time (minutes to days), and a wide tracking temperature range (−70 to +37 °C). Such self-destructive SCLs can be conveniently packaged into flexible TTIs for monitoring the storage and exposure status of diverse vaccines via naked-eye inspection or mobile phone scanning. By overcoming the shortcomings inherent in conventional TTIs and responsive photonic crystals, these self-destructive SCLs can increase their compatibility with cold chain transport and hold promise for the development and application of the next-generation intelligent TTIs and photonic crystals.

Unveiling Enhanced Electrostatic Repulsion in Silica Nanosphere Assembly: Formation Dynamics of Body-Centered-Cubic Colloidal Crystals

“…The calculated volume fraction of dispersions with assembled crystals ranges from ∼1 to ∼5 vol %, based on the density of amorphous and crystalline SiO 2 (Figure d). In contrast, the typical lowest concentration required for SiO 2 nanosphere assembly is ∼30 vol %. ,,, Additionally, it enables the fabrication of photonic crystals with the same color using nanospheres of a much smaller size (84 nm vs 190 nm).…”

“…Decades of investigation have revealed that the ordered self-assembly of these highly charged nanospheres in solution is driven by minimizing the free energy arising from electrostatic repulsive interactions. , Although there is no clear distinction, the reported systems can be roughly classified by the required volume fraction of the colloidal solution. Some systems only show photonic crystals assembled at high volume fractions (i.e., >30 vol %), ,,,, while others do not require such a high concentration (i.e., ∼1–15 vol %). ,, As the ordering of nanoparticles results from electrostatic repulsion, the required volume fraction reflects the effective range of this interaction, which is determined by the thickness of the electrical double layers (EDL).…”

“…Although the self-assembly of PS nanospheres in low-volume fraction solutions has been reported, − ,,,, assembling SiO 2 nanospheres typically requires high-volume-fraction solutions, indicating the lack of sufficiently long-range electrostatic repulsion. ,,, This raises the question of why colloidal SiO 2 nanospheres have difficulty obtaining a thick EDL. In this study, by examining the chemical structure of SiO 2 nanospheres synthesized by the Stöber method, we show that trapped NH 4 + ions in the SiO 2 core are the cause of the issue.…”

Customizable single-layer hydrogel robot with programmable NIR-triggered responsiveness

“…For instance, the integration of temperature-responsive color changes could potentially enable the realization of an unconstrained environmental monitoring system and locally driven soft robot systems. 68 This advancement would expand the application of soft robotics for biomedical applications.…”

Recyclable Cholesteric Phase Liquid Crystal Device for Detecting Storage Temperature Failure

“…Khandelwal et al have developed a static infrared reflector that can block IR radiation from the sun without affecting visible transparency. Huang et al have prepared a temperature monitoring material that self-destructs when it reaches its melting point of the solution, causing irreversible fading of the material; however, this material is not reusable and results in material waste. Furthermore, cholesteric phase liquid crystals at room temperature exhibit bistable states and temperature control characteristics.…”