A biomechanical testing system for single macro-molecules has been developed using optical tweezers. To achieve nanometer manipulation and measurement, a piezo-stage and an interferometer were adopted. A systematic calibration was then performed on the displacement resolution. The piezo- stage has a noise level around 1 nm standard deviation, and the interferometer has a noise level of less than 5 nm standard deviation. The results revealed that the system has a nanometer resolution which is sufficient for the measurement of deformation and stiffness of single macro- molecules.
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