Optical tweezers are a powerful tool to hold and manipulate particles on the microscale. The ability to measure tiny forces enables detailed investigations, e.g., of the mechanical properties of biological systems. Here we present a generally applicable method to simultaneously measure all components of the force applied to a specific particle in a trapped ensemble, or to a specific site of an extended object. This holographic force measurement relies on a detailed analysis of a single interference pattern formed in the far field to recover amplitude and phase of the field. It requires no information about size, shape, or optical properties of the particles and can be scaled to many traps—we show individual force measurements for up to 10 particles. In addition, we demonstrate force measurements when stretching a red blood cell, held directly by four traps. This method opens up a wealth of new opportunities made possible by localized quantitative force measurements in complex biological settings.

中文翻译：

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直接测量捕获的粒子团中的单个光学力

光学镊子是在微尺度上固定和操纵颗粒的强大工具。测量微小力的能力可以进行详细的研究，例如对生物系统的机械性能进行研究。在这里，我们提出了一种普遍适用的方法，用于同时测量施加到被困集合体中特定粒子或扩展对象特定部位的力的所有分量。全息力的测量依赖于对在远场中形成的单个干涉图样的详细分析，以恢复场的振幅和相位。它不需要有关粒子的大小，形状或光学特性的信息，并且可以缩放到许多陷阱，我们可以显示多达10个粒子的单独力测量结果。此外，我们演示了拉伸红细胞时的力测量，由四个陷阱直接保持。这种方法通过在复杂的生物环境中进行局部定量力测量，开辟了许多新的机会。