热驱动法测量光阱刚度的蒙特卡罗模拟

Monte-Carlo Simulation of Optical Trap Stiffness Measurement by Thermalnoise Driven Method

在应用光镊测量微米粒子或生物大分子之间力学特性之前,必须对光镊的光阱刚度进行精确标定,选择精确的标定方法对测量的准确性起着决定作用。采用Monte-Carlo方法,模拟了光阱中的一个粒子在5s时间内其位移随时间变化的信号序列,模拟采样频率为105Hz。基于不同程度噪声和光阱偏移量条件下的模拟实验数据,用三种热驱动力分析法对光阱刚度进行标定。结果表明,三种方法的理想误差均小于2.5%;将粒子位移序列的坐标减去其平均值后得到新的位移序列,然后进行刚度标定,可以消除光阱偏移引入的误差;均方位移法比功率谱法和玻尔兹曼分布法具有更好的抗噪声干扰能力。

Li Jixiang1,2 Yu Youli1,2,3 Zhang Xiaolin1,21School of Science Xi＇an Jiaotong University,Xi＇an,Shaanxi 710049,China2Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter,Ministry of Education,Xi＇an Jiaotong University,Xi＇an,Shaanxi 710049,China3Key Laboratory of Biomedical Information Engineering,Ministry of Education,Xi＇an Jiaotong University,Xi＇an,Shaanxi 710049,China Optical trap stiffness of the optical tweezers must be accurately calibrated,before it is used to measure the mechanical characteristics of submicron particles or biological macromolecules.It is very important to choose a precise calibration method for exact measurement.With Monte-Carlo method,the signal sequence of displacement varies with time during five seconds for a particle in optical trap is simulated,and the simulative sampling frequency is 105 Hz.The optical trap stiffness is calibrated by three thermal-noise-driven analysis methods based on the experimental data in the condition of different noise levels and optical trap deviations.The results show that the ideal errors are all less than 2.5% for the three methods.The errors introduced by optical trap deviation can be eliminated when we calibrate the trap stiffness with the new coordinate of the particle＇s displacement sequence,which is the difference between the original coordinate and its average.The mean square displacement method（MSDM） has a better anti-noise ability than the Boltzmann distribution method（BDM） and power spectrum method（PSM）.