纳米压痕

Abstract(#br)In nanoindentation tests for soft polymers, the elastic modulus estimated from the Hertz model varies with applied force, implying the effect of adhesion work needs to be considered in contact theory. In this article, a hybrid method of combining the Hertz model and the Johnson–Kendall–Roberts (JKR) model is presented, to analytically explain the descending phenomenon of the modulus estimation by considering adhesive effects.

Abstract(#br)In this study, nanomechanical properties of a variety of polymeric materials was investigated by means of AFM. In particular, selecting different AFM probes, poly(methyl methacrylate) (PMMA), polydimethylsiloxane (PDMS) bulk samples, sol–gel hybrid thin films and hydrated hyaluronic acid hydrogels were indented in air to determine the elastic modulus. The force–distance curves and the indentation data were found to be greatly affected by the cantilever stiffness and by tip geometry.

Abstract(#br)Procedure to establish full contact between the sample and the 1\u003cce:hsp sp=\"0.25\"/\u003emm diameter cylindrical flat punch tip to measure polydimethylsiloxane (PDMS) mechanical properties using the Hysitron TriboIndenter is described. This procedure differs from the standard automated indentation because each indent has to be performed manually after establishing full contact with the sample surface. Incomplete contact happens because of the sample tilt with respect to the flat punch surface and results in incorrect elastic modulus values.

Abstract(#br)The mechanical strength and interfacial behavior have been of great significance for composite membranes. In this work, an in-situ nano-indentation/scratch technique was employed to probe mechanical properties and interfacial adhesion of ceramic-supported polydimethylsiloxane (PDMS) composite membranes. The nanostructures of active, transition and support layers were systematically correlated with measured mechanical and adhesive properties, as well as interfacial morphologies and separation performance.

Abstract(#br)Polydimethylsiloxane (PDMS) is one of the widely-used silicone-based organic polymers. It can serve as a substrate to grow cells, mainly because of its controllable range of mechanical properties. Varying the degree of crosslinking in the polymer network allows tuning its mechanical properties in a range similar to living tissues. To study the PDMS stiffness effect on the growth and behavior of cells, it is of significant importance to explore the mechanical properties of a series of PDMS samples cured to different crosslink densities.

Abstract(#br)Nanoindentation can characterize in-situ elastic modulus E of an object by pressing an indenter into the sample surface and fitting the detected data to a contact equation. In this work, we found the conventional contact-mechanism theory resulted in a high uncertainty of E for the hyperelastic materials, including some polymers and biological cells. The evaluated E displayed an exponential decrease with increasing indent distance when fitting to Hertz model and caused high E variance as a function of indent depth.

Nanoindentation is an experimental technique which is attracting increasing interests for the mechanical characterization of articular cartilage. In particular, time dependent mechanical responses due to fluid flow through the porous matrix can be quantitatively investigated by nanoindentation experiments at different penetration depths and/or by using different probe sizes. The aim of this paper is to provide a framework for the quantitative interpretation of the poroelastic response of articular cartilage subjected to creep nanoindentation tests.

We have developed a modified-creep experiment with nanoindenter to measure the viscoelastic properties of elastomer films. Load-controlled experiments on PDMS (polydimethylsiloxane) films were performed using the Nano Indenter\n\t\t\t\t\t\t® XP with a flat-ended tip. By adapting the force–depth relation obtained by Choi et al. [S.T. Choi, S.R. Lee, Y.Y. Earmme, Acta Mater. (submitted for publication)], the indentation results were analyzed to obtain the relaxation modulus of the PDMS film as a function of time.

具有优良柔韧性、导电性和机械耐久性的可拉伸电极是柔性电子新兴和激动人心的领域中最基本的元件。本文提出了一种将银纳米棒( AgNRs )嵌入到聚二甲基硅氧烷( PDMS )基体中，通过独特的角度沉积技术制备这种可拉伸电极的方法。在其中嵌入AgNRs后，PDMS的表面、力学和电学性能都发生了明显的变化。结果表明，AgNRs嵌入PDMS基体后，表面粗糙度和极性增大。由于压痕深度效应，弹性模量( E )和硬度( H )随着压痕载荷的增加而减小。由于AgNRs在PDMS基体中具有很强的界面结合力，纳米复合材料的E和H分别比PDMS膜提高了167.6和93.3 %。此外，AgNRs - PDMS薄膜具有10 - 7 Ω m的电阻率。它在弯曲、扭转、拉伸等各种机械应变下仍保持导电，这一点用发光二极管电路得到了证明。同时，银的抗菌活性使其有望成为可穿戴电子的候选产品。

压痕硬度和划痕试验是工业和实验室常用的测定薄膜力学性能的技术。在这里，我们提出测定由具有弹性性质和自修复效应的聚二甲基硅氧烷和聚硅氧烷混合物组成的薄膜的弹性模量和硬度的相对值。本研究利用显微镜和扫描台设计了一种自制的纳米压痕和纳米划痕测试仪，可对弹性模量较低的透明材料进行测量，并可识别薄膜的自修复效应。