Micro-Scale Mechanical Properties Of Biological Materials Based On Nano-Indentation Technique

The nano-indentation technique, as a method to measure the tissues and other biological materials, is continuously attached an importance to. It becomes a bond between the mechanical properties test of nano-scale by atomic force microscope(AFM)and that of macro-scale by universal test machine(UTM)due to the load range from 1μN to 15N and the indentation depth from 20nm to 30nm. However, there are many differences on the test of the nano-indentation technique and that of micro-scale to general materials,such as the complex on the sample preparation,many influence factors in the experiments, the difficulties of the data analysis and so on,This paper mainly had done some researches on the mechanical properties of biological materials from the following aspects:(1) Because the nano-indentation technique is a method with high demands to the surface of the sample, the sample preparation technique becomes the greatest influence effect to micro-scale biological properties test This paper had done experimental researches with three general methods to prepare the sample including Blood smear method,direct bonding and cold mosaic, it was found that the sample exposed in the air lost the water easily after those general methods are applied, then the bioactivity of the biological samples could not be maintained, so the reliability of the experiments was in decline. Based on the deficiency, the new biological sample preparation technique and the relative test table were developed, the dehydration on the sample caused by the bonding and mosaic was overcome after the test table was applied, and the bioactivity was kept by the humidity kept.(2) Compared with the general material, the biological material had the special mechanical properties due to its intrinsic structure and functions., hence the problem should be fully considered when the test results on the biological samples were analyzed and explained properly. This paper had researches on three types of the structure and functions from the biological materials including the heterogeneity, time effect and the anisotropy, their effects on the nano-indentation experiment were acquired during the experiment, and the evidence was found on the application of the methods and control parameters in the following experiments. (3) It is a medical hot point on how to choose the suitable protection liquid used to maintain the intrinsic properties of the soft bones during the open operations of the soft bones. This paper had the quantitive measurement on the mechanical properties for the articular soft bones protected by the chitin solution and the physiological saline with the new test method applied to the biological samples and the self-made sample table, then the measurement was compared with that of the group exposed in the air, it was shown that it was better to maintain the mechanical properties of soft bones by the chitin solution than that by the physiological saline, and the air had great bad effects on the properties.The experimental results were in accordance with those expected, it provided the proper methods and theory for further micro-scale mechanical properties researches of biological materials, and it was available as a reference to the numerical computation.