Stress and Interface Engineering of Functional Materials

可以说，最重要的一类功能材料是压电性材料。压电性是机械变形和电荷的耦合，是许多先进器件的使能材料特性。目前的应用，包括陀螺仪、加速计和麦克风，对消费电子、汽车和航空航天行业至关重要，这些行业都是加拿大经济的重要分支。此外，创新的微电子机械系统(MEMS)、生物传感器和致动器将需要“物联网”来发展未来的经济。*最新和最创新的设备通常需要高度受限的几何形状的功能材料，如薄膜和纳米纤维。这种小型化导致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，几何图形影响性能的主要机制之一是通过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器件中的功能材料的性能？*优化像压电性这样的独特性能的努力通常涉及改变化学成分或微观结构。残余应力和界面通常被视为负债，而不是可以用来控制基本物理机制的强大工具。然而，要实现包括压电性材料在内的功能材料的全部潜力，需要使用所有可能的操纵方法，通过充分了解适用于现代器件的受限几何形状的调节机制。*本研究计划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，这项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，实现到目前为止难以捉摸的极大增强的材料性能。特别是，目标包括实现高温稳定的压电陶瓷传感器，以及可用作柔性生物传感器的强大的压电聚合物纳米纤维。热稳定的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有利于消费电子和生物医学领域。

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.**