Stress and Interface Engineering of Functional Materials

可以说，最重要的一类功能材料是压电材料。压电是机械变形和电荷的耦合，是许多先进器件的材料特性。目前的应用，包括陀螺仪，加速度计和麦克风，是必不可少的消费电子，汽车和航空航天工业-所有重要的加拿大经济部门。此外，创新的微机电系统（MEMS），生物传感器和执行器将需要通过“物联网”发展明天的经济。最新和最具创新性的设备通常需要高度限制几何形状的功能材料，例如薄膜和纳米纤维。这种小型化使得材料的行为与已经被很好地表征的“大块”材料非常不同。除了界面之外，几何形状影响性能的主要机制之一是局部改变材料所经历的应力状态。这不仅是一个工程挑战，也是一个设计机会：如何利用应力和界面工程来控制这些设备中功能材料的性能？*优化压电性等独特性质的努力通常涉及改变化学成分或微观结构。残余应力和界面往往被视为负债，而不是强大的工具，可以利用来控制潜在的物理机制。然而，要实现包括压电材料在内的功能材料的全部潜力，需要通过充分理解适用于现代设备的有限几何形状下的控制机制，采用所有可能的操作方法。该研究项目开发了一种新的方法来分析这些复杂的应力和界面，并利用它来探索它们对压电材料基本机制的影响。此外，该研究计划研究应力和界面工程作为一种工具，可以超越化学成分和微观结构，以实现迄今为止一直难以捉摸的大大增强的材料性能。特别是，目标包括实现高温稳定的压电陶瓷传感器，以及可以用作柔性生物传感器的强大压电聚合物纳米纤维。热稳定传感器在能源和航空航天工业中将是无价的，而有用的压电聚合物将是消费电子和生物医学领域的布恩。

Arguably the most important class of functional materials is piezoelectrics. Piezoelectricity, the coupling of mechanical deformation and electrical charge, is the enabling material property for many advanced devices. Current applications, including gyroscopes, accelerometers, and microphones, are essential for the consumer electronics, automotive, and aerospace industries - all important branches of the Canadian economy. In addition, innovative microelectromechanical systems (MEMS), biosensors, and actuators will be needed to develop tomorrow's economy with the "internet of things".***The newest and most innovative devices often require functional materials in highly restricted geometries, such as thin-films and nanofibers. This miniaturization causes materials to behave very differently from the "bulk" materials that have been so well characterized. In addition to interfaces, one of the primary mechanisms by which geometry can affect properties is by locally altering the stress state experienced by the material. This is not only an engineering challenge, but also a design opportunity: how can stress and interface engineering be employed to control the properties of functional materials in these devices?***Efforts to optimize a unique property like piezoelectricity typically involve varying the chemical composition or microstructure. Residual stresses and interfaces are often seen as liabilities rather than powerful tools that can be harnessed to control the underlying physical mechanisms. However, realizing the full potential of functional materials, including piezoelectrics, requires employing all possible methods of manipulation by developing an adequate understanding of governing mechanisms at the restricted geometries applicable to modern devices.***This research program develops a novel method for analyzing these complex stresses and interfaces, and uses it to explore their effect on the fundamental mechanisms in piezoelectric materials. Further, this research program investigates stress and interface engineering as a tool that can go beyond chemical composition and microstructure to realize greatly enhanced material properties that have so far been elusive. In particular, the objectives include enabling high-temperature stable piezoelectric ceramic sensors, as well as powerful piezoelectric polymer nanofibers that can act as flexible biosensors. A thermally stable sensor would be invaluable in the energy and aerospace industries, while a useful piezoelectric polymer would be a boon to the consumer electronics and biomedical fields.**