Vacuum Fluctuation Induced Torque on Liquid Crystal Molecules

这个项目的目标是寻找一种新的效果，预计这种效果可以在微尺度上旋转小物体，而不需要使用重力或静电等传统力量。根据量子力学，也就是研究自然如何在超小尺度上工作的理论，“空白空间”实际上充满了活力。即使当所有粒子都从一个空间区域移走时，波动的电磁波也被发现是持续存在的。如果两块不带电荷的金属板在“空隙”中靠得很近，这些电磁波就会施加力，把两块金属板推到一起，就像波涛汹涌的水中的两艘船一样。这种将金属板推到一起的力被称为卡西米尔力，它纯粹是量子力学的结果。空旷空间中起伏不定的磁场会导致物体旋转吗？根据量子力学，答案是肯定的！为此，对象需要具有随方向变化的反射属性，以致力会导致这些对象旋转，而不仅仅是被推到一起。这种旋转可以用来帮助设计更高效、更有用的微电子机械系统(MEMS)，比如安全气囊和手机中的系统。首席研究人员的目标是对这种旋转效应进行第一次测量，即所谓的卡西米尔扭矩，这将在一个由大块晶体附近的液晶分子组成的系统上进行。此外，这项工作将促进我们对量子力学的理解，以及如何利用量子力学来改进已经变得无处不在的小规模设备的知识。当光学各向异性材料放置在非常接近的地方时，材料对零点电磁涨落施加的边界条件将导致与角度有关的能量密度。为了最小化系统的总能量，对象将旋转。首席研究人员的目标是使用全光学测量技术测量光学各向异性液晶在靠近双折射平板时的旋转率。入射光将通过液晶传播，液晶的取向由于卡西米尔扭矩而扭曲，当离开系统时，将测量光的最终偏振态。光强度将被用来确定液晶在与双折射板不同的分离时所产生的卡西米尔扭矩所产生的扭矩。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.