Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, NY, 14853, USA.
Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA.
Small. 2023 Jun;19(23):e2207802. doi: 10.1002/smll.202207802. Epub 2023 Mar 9.
Identifying and removing microplastics (MPs) from the environment is a global challenge. This study explores how the colloidal fraction of MPs assemble into distinct 2D patterns at aqueous interfaces of liquid crystal (LC) films with the goal of developing surface-sensitive methods for identifying MPs. Polyethylene (PE) and polystyrene (PS) microparticles are measured to exhibit distinct aggregation patterns, with addition of anionic surfactant amplifying differences in PS/PE aggregation patterns: PS changes from a linear chain-like morphology to a singly dispersed state with increasing surfactant concentration whereas PE forms dense clusters at all surfactant concentrations. Statistical analysis of assembly patterns using deep learning image recognition models yields accurate classification, with feature importance analysis confirming that dense, multibranched assemblies are unique features of PE relative to PS. Microscopic characterization of LC ordering at the microparticle surfaces leads to predict LC-mediated interactions (due to elastic strain) with a dipolar symmetry, a prediction consistent with the interfacial organization of PS but not PE. Further analysis leads to conclude that PE microparticles, due to their polycrystalline nature, possess rough surfaces that lead to weak LC elastic interactions and enhanced capillary forces. Overall, the results highlight the potential utility of LC interfaces for rapid identification of colloidal MPs based on their surface properties.
从环境中识别和去除微塑料（MPs）是一项全球性挑战。本研究探索了 MPs 的胶体部分如何在液晶（LC）薄膜的水相界面上组装成不同的 2D 图案，目的是开发用于识别 MPs 的表面敏感方法。测量到聚乙烯（PE）和聚苯乙烯（PS）微颗粒表现出不同的聚集模式，添加阴离子表面活性剂放大了 PS/PE 聚集模式的差异：随着表面活性剂浓度的增加，PS 从线性链状形态变为单一分散状态，而 PE 在所有表面活性剂浓度下形成密集的簇。使用深度学习图像识别模型对组装模式进行统计分析可实现准确分类，特征重要性分析证实，与 PS 相比，密集的多分支组装是 PE 的独特特征。对微颗粒表面 LC 有序性的微观表征导致预测 LC 介导的相互作用（由于弹性应变）具有偶极对称性，这一预测与 PS 但与 PE 的界面组织一致。进一步的分析得出结论，PE 微颗粒由于其多晶性质，具有粗糙的表面，导致 LC 弹性相互作用较弱和毛细作用力增强。总的来说，这些结果强调了 LC 界面在基于 MPs 表面特性快速识别胶体 MPs 方面的潜在应用。
