Reichstein Jakob, Müssig Stephan, Bauer Hannes, Wintzheimer Susanne, Mandel Karl
Department of Chemistry and Pharmacy, Inorganic Chemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Egerlandstraße 1, D-91058, Erlangen, Germany.
Fraunhofer-Institute for Silicate Research ISC, Neunerplatz 2, D-97082, Würzburg, Germany.
Adv Mater. 2022 Aug;34(31):e2202683. doi: 10.1002/adma.202202683. Epub 2022 Jun 30.
Small-sized temperature indicator additives autonomously record temperature events via a gradual irreversible signal change. This permits, for instance, the indication of possible cold-chain breaches or failure of electronics but also curing of glues. Thus, information about the materials' thermal history can be obtained upon signal detection at every point of interest. In this work, maximum-temperature indicators with magnetic readout based on micrometer-sized supraparticles (SPs) are introduced. The magnetic signal transduction is, by nature, independent of the materials' optical properties. This facilitates the determination of valuable temperature information from the inside, that is, the bulk, even of dark and opaque macroscopic objects, which might differ from their surface. Compared to state-of-the-art optical temperature indicators, complementary magnetic readout characteristics ultimately expand their applicability. The conceptualized SPs are hierarchically structured assemblies of environmentally friendly, inexpensive iron oxide nanoparticles and thermoplastic polymer. Irreversible structural changes, induced by polymer softening, yield magnetic interaction changes within and between the hierarchic sub-structures, which are distinguishable and define the temperature indication mechanism. The fundamental understanding of the SPs' working principle enables customization of the particles' working range, response time, and sensitivity, using a toolbox-like manufacturing approach. The magnetic signal change is detected self-referenced, fast, and contactless.
小型温度指示添加剂通过逐渐不可逆的信号变化自主记录温度事件。例如，这可以指示可能的冷链中断或电子设备故障，也可用于胶水固化。因此，在每个感兴趣的点进行信号检测时，都可以获得有关材料热历史的信息。在这项工作中，引入了基于微米级超粒子（SPs）的具有磁读出功能的最高温度指示器。磁信号转导本质上与材料的光学性质无关。这便于从内部，即从物体整体，甚至是深色和不透明宏观物体的内部确定有价值的温度信息，而这些信息可能与它们的表面不同。与现有技术的光学温度指示器相比，互补的磁读出特性最终扩展了它们的适用性。概念化的超粒子是由环境友好、价格低廉的氧化铁纳米颗粒和热塑性聚合物组成的分层结构组件。聚合物软化引起的不可逆结构变化会导致分层子结构内部和之间的磁相互作用发生变化，这些变化是可区分的，并定义了温度指示机制。对超粒子工作原理的基本理解使得能够使用类似工具箱的制造方法来定制粒子的工作范围、响应时间和灵敏度。磁信号变化可通过自参考、快速且非接触的方式进行检测。
