AI 中文总结
研究用球形尖端原子力显微镜探针在大压痕下对薄弹性膜和活细胞进行力学映射，提出考虑底部效应的分析模型，经实验验证，该模型能准确校正底部效应，为细胞提供准确杨氏模量值，与其他模型有显著差异，展现分析力曲线测量的潜力。
AI 中文摘要
本文提出了一个分析模型，用于量化用球形尖端原子力显微镜（AFM）探针在弹性薄膜和活细胞上获得的大压痕力曲线。该模型考虑了整个压痕范围内的底部效应，克服了适用于半无限厚样品的Sneddon和Hertz接触模型以及仅适用于相对小压痕的具有底部效应校正（BEC）的抛物面尖端模型的局限性。通过对聚丙烯酰胺（PAA）水凝胶薄膜的力体积测量对该模型进行了实验验证，获得了极好的一致性。底部效应的精确校正表明，PAA薄膜的固有杨氏模量在厚度低于临界值（约15μm）时会增加。该模型与在活巨噬细胞上获得的力曲线也显示出极好的一致性，为这些非常柔软的细胞提供了准确的杨氏模量值（E~200Pa）。用所提出的模型提取的杨氏模量值与从具有BEC的Sneddon或抛物面模型获得的值有显著差异，后者的值分别偏差100%和-25%。结果表明了所提出的模型在分析薄膜弹性材料和活细胞在微米和纳米尺度上大压痕下球形尖端力曲线测量方面的潜力。
英文摘要
An analytical model to quantify large indentation force curves acquired on elastic thin films and living cells with spherical tip Atomic Force Microscopy (AFM) probes is presented. The model accounts for the bottom effect in the whole indentation range and overcomes the limitations of Sneddon's and Hertz's contact models, which are valid for semi-infinite thick samples, and of paraboloid tip models with bottom effect correction (BEC) that are applicable to spherical tips only for relatively small indentations. The model is experimentally validated with force volume measurements on polyacrylamide (PAA) hydrogel thin films, where an excellent agreement is obtained. The accurate correction of the bottom effect demonstrates that the intrinsic Young's modulus of PAA thin films increases for thickness below a critical value (~15 um). The model also shows excellent agreement with force curves acquired on live macrophages, providing accurate Young's modulus values for these very soft cells (E~200 Pa). Young's modulus values extracted with the proposed model significantly differ from those obtained from Sneddon's or paraboloid models with BEC, whose values deviate by 100% and -25%, respectively. Results show the potential of the proposed model for analysing force curve measurements with spherical tips at large indentations on thin film elastic materials and living cells at the micro and nanoscale.
