Elasticity measurement of DNA origami nanotube in liquid with tapping mode AFM

The elasticity of nanomaterial is extremely difficult to be obtained with traditional method due to their ultra-small scale. AFM provide a feasible way to solve this problem, but it still meets many challenges especially for the measurement of one dimensional material such as DNA origami nanotube, CNT, Silicon Nanowire and so on. In addition to the influence aroused from the sample surface effect, locating the probe exactly over the 1D material with nano-diameter is hard to achieve due to the nonlinearity of PZT actuator and the thermal drift. In this study, a new method is proposed to overcome these shortcomings. It is a physical calculation process combined with experimental measurement results to deduce the elasticity of one dimensional material. This method starts at an assumed elasticity of nanomaterials, and then experimental elasticity can be obtained based on scanned image in tapping mode. The elasticity with minimized error between assumed one and experimental one should be the true value of the materials. Since with the imaging scan method, the exactly locating the probe over the sample is not necessary. In addition, due to accurately controllable tapping force, the deformation of the nanomaterial can be controlled within a tiny scale, thus the influence from the sample surface effect can be get rid of effectively. The elasticity (pre-known) of polystyrene is measured to demonstrate the effectiveness of the proposed method. The elasticity of DNA origami is also first time obtained with the proposed method, which shows an elasticity range between 75MPa and 180 MPa. This method is simple and can be used to measure other soft nano-materials.