Innovative Tunable Optical Properties in Nanocrystal-based Films by Employing Mechanical Instabilities

健康监测、能源储存和使用以及通信技术的未来正朝着灵活、可弯曲和可拉伸的设备发展，包括可穿戴设备和“电子皮肤”。为了最大限度地发挥这些应用的潜力，需要发现既能表现出令人兴奋的光学和电子特性，又能保持机械柔性系统一部分的材料。纳米晶体为研究这一目的提供了一个理想的系统，因为它们具有可调谐的电磁吸收和发射特性，制造简单且价格低廉，并且可以集成到可拉伸基板上的薄膜中。尽管如此，对这些体系的变形行为的研究还很少。该奖项支持在可变形和柔性基板上创建发光纳米晶体薄膜的研究，以测量其光学和机械性能，并描述和预测这些薄膜在弯曲/拉伸期间的行为。这些系统的预计应用包括形成光学超材料，如可调谐光栅和滤波器，用于身体度量的可穿戴传感器，以及柔性能源设备（例如，发光设备和太阳能光伏）。研究方法是结合机械工程、材料科学和纳米技术的思想，以建立对纳米晶体层如何可控变形的强大理解。这项研究将用于全年的外展活动，以激励和教育未来的工程师，包括与公众的互动，以及针对代表性不足群体的目标活动。纳米晶体通常用于传统的刚性电子器件，具有承受可变形器件操作的应变的潜力。此外，它们可以使用环保技术和材料制成，并表现出令人兴奋的尺寸相关特性，如发光。此外，在预拉伸弹性体衬底上的纳米晶体薄膜中，由于不稳定形成的可调起皱可用于生成新的电磁和声学超材料。问题是纳米晶体薄膜对薄膜基底拉伸/弯曲的力学响应几乎是完全未知的。本研究将致力于从实验和理论上填补这一知识空白。研究将包括纳米晶体/衬底系统的力学行为和不稳定形成的实验研究，这取决于纳米晶体尺寸和薄膜孔隙率/厚度。这些研究将通过系统力学特性的理论建模来补充，以描述不稳定的形成。该研究将被整合并用于预测和设计纳米晶体薄膜的不稳定性，最终应用于可拉伸电子、传感器和光学/声学超材料。

The future of technology for health monitoring, energy storage and use, and communications is moving towards flexible, bendable, and stretchable devices, including wearable devices and "electronic skins". To reach the maximum potential of these applications, there is a need to discover materials that exhibit exciting optical and electronic properties while remaining part of a mechanically flexible system. Nanocrystals present an ideal system to investigate for this purpose, as they have tunable electromagnetic absorption and emission properties, are easy and inexpensive to make, and can be integrated into thin films on stretchable substrates. Despite this, there have been few studies on the deformation behavior of these systems. This award supports research to create thin films of luminescent nanocrystals on deformable and flexible substrates, to measure their optical and mechanical properties, and to describe and predict the behavior of these films during flexion/stretching. The projected applications of these systems include forming optical metamaterials such as tunable gratings and filters, wearable sensors for body metrics, and flexible energy devices (e.g., light-emitting devices and solar photovoltaics). The research approach is to combine ideas across mechanical engineering, materials science, and nanotechnology to create a robust understanding of how layers of nanocrystals can be controllably deformed. This research will be used in year-round outreach events to inspire and educate future engineers including interactions with the general public and targeted events for underrepresented groups.Nanocrystals, used often in traditional rigid electronic devices, have the potential to withstand the strain of deformable device operation. Moreover, they can be made using environmentally friendly techniques and materials and exhibit exciting size-dependent properties such as luminescence. In addition, tunable wrinkling, due to instability formation, in thin films of nanocrystals on pre-stretched elastomeric substrates can be used to generate new electromagnetic and acoustic meta-materials. The problem is that the mechanical responses of nanocrystal films to stretching/flexion of the film substrate are almost completely unknown. This research will be devoted to experimentally and theoretically filling this knowledge gap. The research will include experimental studies on the mechanical behavior and instability formation in nanocrystal/substrate systems, depending on nanocrystal size and film porosity/thickness. These studies will be complemented by theoretical modeling of the mechanical properties of the systems to describe the instability formation. The research will then be integrated and used for predicting and designing the instabilities in nanocrystal films with ultimate application areas in stretchable electronics, sensors, and optical/acoustic metamaterials.