纳米力学测试系统在生物材料方面的应用

       生物样品在流体环境下的力学性能与实验室干燥环境下的力学性能差异很大，因此在流体介质中探测生物样品的力学特性，测量的数据更接近生物样品在工作环境中的真实情况。那么如何在流体介质中测量生物样品的力学特性及数据呢？       NanoTest在纳米力学测试系统上加入了液体池模块，可以对完全浸入液体池中的样品进行纳米压痕、纳米划痕和磨损测试，摩擦传感器也可使浸入样品进行摩擦测量。该液体池采用现有的摆设计，水平加载在流体测试中具有以下优势：a、浮力恒定，b、恒定表面张力，c、液体不经过电容器之下。                             NanoTest 纳米力学测试系统的液体池模块能对生物材料、组织、细胞器、细胞层、软骨、静电支架、牙釉质等在液体环境中进行力学性能表征，不仅为生物材料以及组织研究人员和工程师提供完美的解决方案，也是组织工程和再生医学的研究者衡量他们感兴趣材料刚度的良好选择。 例如：研究生物材料大范围的刚度值：麻省理工学院的研究表明，纳米测试液体细胞的纳米压痕可以在样品完全浸入液体的情况下进行，从高度柔顺的凝胶到生物组织，材料的硬度跨越几个数量级。图3显示了不同样品的弹性模量与文献值非常吻合。数据的范围是8个数量级。Micro MaterialsExcellence in NanomechanicsLiquid Cell Liquid Cell module wit h the NanoTes t Vanta g e Mechanical properties of biological samples often vary considerably when in their normal fluid environment compared to the usual laboratory dry testing condi t ions. Probing the mechanical properties of biological samples in f luid media should prove a closer mimic of in vivo conditions than conventional dry nanoindentation tes ti ng. Research by MIT has shown that nanoindentat i on with the NanoTest liquid cell could be performed with sample fully i mmersed in liquid for materials spanning several orders of magnitude of s t i f fness f rom highly compliant gels， biological tissues to glasses. How i t works The testing capabi l i t y o f the NanoTes t has bee n extended by the development of a li qu i d cell allowing Nanoindentatio n ， Nano-scratch & Wear testing of samples fully immersed in liquid. A frict i on transducer extension also al l ows immersed sample f r ict i on measurements.The f l uid cell works with the existing pendulum design and t he horizontal loading has several key advantages for testing in fluid. Constant buoyancy force Constant surface tension on loading column Liquid is not underneath capacitor L i quid c el l a p pl ica tion s an d invest i g ati ng o f so f t ma teri al s imm e rs ed i n liqu i d s includ e s ： Tribology Corrosion T i ssue mechanics as a function of source， disease state， and exposure to soluble tox i ns or drugs Tissue properties as a function of submicron position wi t hin the tissue Porous materials (bone， cement， chemomechanics) Biocompatibility and biomaterials Dental enamel Micro partic l e friction and wear Polishing mechanics Liquid Cell nanomechanical measureme nt s in fully hydrated in -s i tu conditions Figure 4 shows that when hydrolytic attack and plasticization occurs， polymer stiffness decreases significantly [...see also G.A Bell， DM Bielinski and BD Beake， J ApplPolymSci 107(2008) 577]. Figure 3 shows the measured Elastic modulii of various specimens (Borosilicate glass， Polypropylene， Porcine liver， Porcine skin， PAAm-gels in various mol concentrations) are in very good agreement with literature values. Data ranges over eight orders of magnitude. “This liquid cell feature has enabled us to explore the mechanical proper t ies of hydrated materials， which is part i cularly important to our studies of bio l ogically relevant and biodegradable surfaces andwhich i s not accessible to us through other i n s t rumentation wi t h comparable rang e s o f calibrated force and depth". Professor Krystyn J. Van Vliet， MIT Department of Materials Science and Engineering NanoTest Van t a g e Wet vs. dry： Measurement o f nanomec h anical p rope r ties of hydrogels Figure 6 shows that the differences between the nanoindentation response of PAA hydrogel under dry and wet condit i ons are str i king.The effect of submerging these samples in water， using The NanoTest Vantage liquid cell ， with a 30 second hold at the peak load for creep， shows very significant softening and greatly increased creep during the dwell period， behaviour that is directly comparable to hydrogels tested in wet conditions by MIT [...for similar work see G. Constantinides et al. / Journal of Biomechanics 41 (2008) 3285-3289]. I n denter adapter allow s indente r to b e im merse d i n c el l Ea se of c al i b r ati on， set u p a nd indenter excha n g e L a r g e d e pth rang e availabl e 卜 L iquid C e ll can be heat e d to bod y t e m pe r at ur e or abov e (no iss u es wit h steami n g the capa ci ti ve se n sor)F l u i d exc ha nge duri ng exper i ment is pos sib le (f l ow cell o p ti on )Auto m at ed s c he d u l es Figure 7 shows that i n liquid there i s an increase in indentation creep over 600 s. With the high level of stability of The NanoTest Vantage i t is possible to look at time dependent proper t ies over long contac t t i mes withou t loss of accuracy from t hermal drift. Local MML Representative Micro Materials Ltd NanoTest Van t age Willow House， Yale Business Villag e Ellice Way， Wrexham LL13 7YL， UK Tel ： +44 1978261615 info@micromaterials.co.uk www.micromaterials.co.uk