3D printed liquid crystal elastomers: symmetry, order, structure and mechanics

不断需要新的聚合物来满足现代世界不断变化的挑战。安全消散冲击和振动就是这样一个领域，我们需要新的软材料（例如）在自行车事故中保护我们的头部，以及在北海恶劣环境中保护风力涡轮机叶片免受雨水侵蚀的涂层。这些应用需要设计精细平衡的粘弹性材料，这些材料具有弹性和保持形状；能耗散大量的机械能；并且足够轻，可以满足更广泛的应用需求。液晶弹性体（LCEs）是解决这些挑战的一种很有前途的材料。当宏观排列时，例如通过使用直接墨水书写的3D打印，lce的耗散特性进一步增强。在一个简单的层面上，3D打印过程导致液晶聚合物链在从打印喷嘴挤出时发生剪切对齐。在现实中，对准的结构和大小有一个复杂的依赖于许多参数，如粘度，打印速度和喷嘴几何形状。该项目将研究打印参数如何影响打印液晶弹性体的链对齐和物理性能。根据学生的背景、兴趣和技能，本项目可以灵活地从实验或模拟（或两者兼而有之）的角度来解决问题。从实际应用的角度来看，研究将集中在：打印LCE器件并系统地改变打印参数；测量印刷器件的结构和顺序；以及表征印刷材料的物理特性。从模拟的角度来看，该项目将创建3D打印LCEs的流体动力学模型，以了解打印条件和墨水特性如何相互作用，从而决定打印设备的顺序和特性。这两种方法都旨在实现具有特定冲击吸收和减振应用的3D打印LCE设备的设计。

New polymers are continually needed to meet the modern world's evolving challenges. The safe dissipation of impacts and vibrations is one such area where we need new soft materials to (for example) protect our heads in bicycle accidents, and in coatings to protect wind turbine blades against the effects of rain erosion in the harsh environment of the North Sea.These applications require design of finely balanced viscoelastic materials which: are elastic and shape-retaining; can dissipate large quantities of mechanical energy; and are light enough to meet the broader application requirements.One such promising class of materials to address these challenges are liquid crystal elastomers (LCEs). The dissipative properties of LCEs are further enhanced when macroscopically aligned - for instance through 3D printing using direct-ink writing. On a simple level, the 3D printing process causes shear-alignment of the liquid crystal polymer chains as they are extruded from the printing nozzle. In reality, the structure and magnitude of the alignment has a complex dependence on many parameters such as viscosity, print speed, and nozzle geometry.This project will investigate how printing parameters affect the chain alignment and physical properties of printed liquid crystal elastomers. This project has the flexibility to approach the problem from an experimental or simulations (or both!) point of view depending on the student's background, interests and skills. From a practical point of view, the research would focus on: printing LCE devices and systematically changing the printing parameters; measuring the structure and order of printed devices; and characterising the physical properties of printed materials. From a simulations point of view, this project would create a fluid dynamics model of 3D printed LCEs to understand how print conditions and ink properties interact to dictate the ordering in, and properties of printed devices. Both approaches will aim to enable the design of 3D printed LCE devices with specific impact absorbing and vibration damping applications.