Vacuum Fluctuation Induced Torque on Liquid Crystal Molecules

该项目的目标是寻找一种新的效应，可以在不使用重力或静电等传统力的情况下在微观尺度上旋转小物体。根据量子力学，即研究大自然如何在超小尺度上运作的学科，“真空”实际上充满了活动。即使所有的粒子都从空间区域中移除，波动的电磁波也会持续存在。如果两个不带电的金属板在“真空”中相互靠近，这些电磁波就会施加一种力，把两个板推到一起，就像两艘船在波涛汹涌的水中一样。这种将金属板推到一起的力被称为卡西米尔力，纯粹是量子力学的结果。真空中的波动场会导致物体旋转吗？根据量子力学，答案是肯定的！为此，物体需要具有随方向变化的反射特性，这样力就会使这些物体旋转，而不仅仅是被挤在一起。这种旋转可以用来帮助设计更高效、更有用的微机电系统（MEMS），就像安全气囊和手机中的系统一样。首席研究员的目标是对这种旋转效应进行首次测量，即所谓的卡西米尔扭矩，这将在一个由靠近大块晶体的液晶分子组成的系统上进行。此外，这项工作将推进我们对量子力学的理解，以及我们如何利用量子力学改进无处不在的小型设备的知识。当光学各向异性材料放置在较近的位置时，材料对零点电磁波动施加的边界条件将导致角相关的能量密度。为了使系统的总能量最小，物体将旋转。主要研究者的目标是利用全光学测量技术测量靠近双折射板的光学各向异性液晶的旋转。入射光通过液晶传播，由于卡西米尔扭矩的作用，液晶的取向发生了扭曲，光在离开系统时的最终偏振态将被测量。光强度将用于确定在与双折射板的不同距离处由卡西米尔扭矩引起的液晶所经历的扭矩。这种分离由沉积在双折射晶体和液晶之间的各向同性间隔层控制。该测量技术避免了对机械运动的检测，既简化了检测，又提高了测量灵敏度。

The goal of this project is to search for a new effect that is predicted to rotate small objects on the micro-scale without the use of traditional forces like gravity or electrostatics. According to quantum mechanics, i.e. the study of how nature works on the ultra-small-scale, "empty space" is actually teeming with activity. Even when all particles are removed from a region of space, fluctuating electromagnetic waves are found to persist. If two uncharged metal plates are brought near each other in "empty space," these electromagnetic waves exert a force, which pushes the two plates together, much like two ships in choppy water. This force that pushes the metal plates together is known as the Casimir force, and is purely a result of quantum mechanics. Could the fluctuating fields in empty space cause objects to rotate? According to quantum mechanics, the answer is yes! For that, the objects need to have reflective properties that vary with orientation so that the force would cause these objects to rotate rather than just be pushed together. This rotation could be used to help design more efficient and useful micro-electro-mechanical systems (MEMS), like the ones found in airbags and cell phones. The principal investigator aims to perform the first measurement of this rotational effect, the so-called Casimir torque, which will be carried out on a system consisting of liquid crystal molecules near a bulk crystal. In additional, this work will advance our understanding of quantum mechanics and our knowledge of how it can be used to improve small-scale devices, which have become ubiquitous.When optically anisotropic materials are placed in close proximity, the boundary conditions imposed by the materials on the zero-point electromagnetic fluctuations will cause an angle dependent energy density. In order to minimize the total energy for the system, the objects will rotate. The principal investigator aims to measure the rotation of an optically anisotropic liquid crystal in close proximity to a birefringent plate using an all-optical measurement technique. Incident light will propagate through the liquid crystal, whose orientation is twisted as a result of the Casimir torque, and the final polarization state of the light will be measured upon exiting the system. The light intensity will be used to determine the torque experienced by the liquid crystal resulting from the Casimir torque at various separations from the birefringent plate. The separation is controlled by an isotropic spacer layer deposited between the birefringent crystal and the liquid crystal. The measurement technique avoids the need for detection of mechanical motion, which both simplifies the detection and improves the measurement sensitivity.