Research On The Theory And Method Of Micro- Force Measurement And Tracing

Micro-force is widely used in biomedicine, new materials, microelectronics and other fields. It is the establish of a high accuracy of measurement standards that ensures the sustainable and rapid development of micro-nano technology. In this paper, to link force measurement result to International System of Units(SI), a high accuracy measurement standard is established and appropriate transport way and methods is adopted. To realize and transport the micro-force, electrical method is adopted via the accurate measurement of electrical signal and geometry. For the system is susceptible to environmental disturbances, this paper focuses on the anti-interference techniques. Based on stiffness of cantilever, force standard transmission scheme is studied and the theoretical analysis and experimental verification is completed.In this paper, the main work is as follows:1.We analyze the domestic and foreign research status in the field of micro-force measurement systematically. Force measurement system is constructed, consisting of dC/dz measurement module, the electrode equilibrium position monitoring module and error compensation module, data processing and force computing module.2.The anti-interference techniques are studied in this paper. The effect of the ground vibration, air flowing, electromagnetic interference and the thermal noise of the spring support are discussed in detail. The air damping is introduced to optimize system stability. Result from the air damping experiment shows that the damping ratio increases from 0.0005 to 0.1, which improves environmental noise suppression. And the maximum displacement decreased from about 1 μm to 0.1 μm by the adding of air damping. Electromagnetic shielding reduces the influence of electromagnetic interference on capacitance measurement. Newton method is adopted to reduce the effect of thermal noise of spring support in force measurement.3. We determined the dC/dz, whose mean is 0.9269 pF/mm, standard deviation is 0.0006 pF/mm and relative standard deviation is 0.067 %. The uncertainty source causing the measurement of dC/dz is analyzed and the proper method is adopted to improve the accurate of dC/dz. The electrostatic force is compared to standard weight, analyzed the uncertainty, consisting of ground vibration, air influence(type A) and dC/dz, voltage source, laser interferometer(type B). The results show that the combine uncertainty is less than 2%.4. Based on electrostatic field, the force standard transport is studied. We investigate a method, which is rapid and reliably way of accurately determining spring constant of cantilevers, based on electrostatic force and vibration. In this method, the spring constant of cantilevers can be determined by measuring their resonant frequencies before and after touching the cantilever to known large scale flexible hinged parallelogram. Brief modeling of the method is shown in the paper.5. The multi-position calibration method for AFM cantilevers is investigated. The position providing minimum uncertainty is deduced. The relationship between the measurement loading position and the resultant uncertainty is investigated to determine the location which minimises this factor. The validity of the multi-position approach is shown via theoretical and experimental means. The results show that the combine uncertainty is less than 8% for the cantilever with stiffness of 0.1N/m.