Wenderoth Sarah, Bleyer Gudrun, Endres Jakob, Prieschl Johannes, Vogel Nicolas, Wintzheimer Susanne, Mandel Karl
Chair of Chemical Technology of Materials Synthesis, Julius-Maximilians-University Würzburg, Röntgenring 11, D97070, Würzburg, Germany.
Fraunhofer-Institute for Silicate Research ISC, Neunerplatz 2, D97082, Würzburg, Germany.
Small. 2022 Dec;18(48):e2203068. doi: 10.1002/smll.202203068. Epub 2022 Oct 17.
Optical microscale shear-stress indicator particles are of interest for the in situ recording of localized forces, e.g., during 3D printing or smart skins in robotic applications. Recently developed particle systems are based on optical responses enabled by integrated organic dyes. They thus suffer from potential chemical instability and cross-sensitivities toward humidity or temperature. These drawbacks can be circumvented using photonic balls as shear-stress indicator particles, which employ structural color as the element to record forces. Here, such photonic balls are prepared from silica and iron oxide nanoparticles via the scalable and fast spray-drying technique. Process parameters to create photonic balls with a disordered core and an ordered particle structure toward the exterior of the supraparticles are reported. This hybrid disordered-ordered structure is responsible for a color loss of the indicator particles during shear-stress application because of irreversible structural destruction. By adjusting the primary silica particle sizes, nearly all colors of the visible spectrum can be achieved and the sensitivity of the response to shear stress can be adjusted.
光学微尺度剪应力指示颗粒对于原位记录局部力很有意义，例如在3D打印或机器人应用中的智能皮肤制作过程中。最近开发的颗粒系统基于集成有机染料实现的光学响应。因此，它们存在潜在的化学不稳定性以及对湿度或温度的交叉敏感性。使用光子球作为剪应力指示颗粒可以规避这些缺点，光子球利用结构色作为记录力的元素。在此，这种光子球通过可扩展且快速的喷雾干燥技术由二氧化硅和氧化铁纳米颗粒制备而成。报告了用于制备具有无序核心和朝向超颗粒外部的有序颗粒结构的光子球的工艺参数。这种混合的无序-有序结构是剪切应力施加过程中指示颗粒颜色损失的原因，这是由于不可逆的结构破坏。通过调整原生二氧化硅颗粒尺寸，可以实现可见光谱的几乎所有颜色，并且可以调整对剪应力响应的灵敏度。
