Simmons R M, Finer J T, Chu S, Spudich J A
MRC Muscle and Cell Motility Unit, Randall Institute, King's College London, England.
Biophys J. 1996 Apr;70(4):1813-22. doi: 10.1016/S0006-3495(96)79746-1.
We combined a single-beam gradient optical trap with a high-resolution photodiode position detector to show that an optical trap can be used to make quantitative measurements of nanometer displacements and piconewton forces with millisecond resolution. When an external force is applied to a micron-sized bead held by an optical trap, the bead is displaced from the center of the trap by an amount proportional to the applied force. When the applied force is changed rapidly, the rise time of the displacement is on the millisecond time scale, and thus a trapped bead can be used as a force transducer. The performance can be enhanced by a feedback circuit so that the position of the trap moves by means of acousto-optic modulators to exert a force equal and opposite to the external force applied to the bead. In this case the position of the trap can be used to measure the applied force. We consider parameters of the trapped bead such as stiffness and response time as a function of bead diameter and laser beam power and compare the results with recent ray-optic calculations.
我们将单光束梯度光阱与高分辨率光电二极管位置探测器相结合，以证明光阱可用于以毫秒分辨率对纳米位移和皮牛顿力进行定量测量。当外力施加到由光阱捕获的微米级珠子上时，珠子会从阱中心位移，位移量与施加的力成正比。当施加的力快速变化时，位移的上升时间在毫秒时间尺度上，因此被捕获的珠子可作为力传感器。通过反馈电路可提高性能，使阱的位置借助声光调制器移动，以施加与施加到珠子上的外力大小相等、方向相反的力。在这种情况下，阱的位置可用于测量施加的力。我们将被捕获珠子的参数（如刚度和响应时间）视为珠子直径和激光束功率的函数，并将结果与最近的光线光学计算进行比较。
