Nanomechanical Measurements Research Articles

The Assessment of Organic Matter Young's Modulus Distribution With Depositional Environment and Maturity

AbstractQuantification of risk to seal integrity in CCS, or gas extraction from hydraulic fracturing, is directly affected by the accessibility of organic pores within organic rich mudrocks. Knowledge of the host organic matter's mechanical properties, which are influenced by depositional environment and thermal maturity, are required to reduce operational risk. In this study we address the effect of both depositional environment and maturity on organic matter Young's modulus by means of Atomic Force Microscopy Quantitative ImagingTM, which is a nondestructive technique capable of nanomechanical measurements. Shales from varying marine depositional environments covering kerogen Types II (Barnett), IIS (Tarfaya), and II/III (Eagle Ford/ Bowland) are analyzed to capture variance in organic matter. The findings show organic matter has a Young's modulus ranging between 0.1 and 24 GPa. These marine shales have a bimodal distribution of Young's modulus to some degree, with peaks at between 3–10 and 19–24 GPa. These shales exhibit a trend with maturity, whereby Young's modulus values of <10 GPa are dominant in immature Tarfaya shale, becoming similar to the proportion of values above 15 GPa within the oil window, before the stiffer values dominate into the gas window. These peaks most likely represent soft heterogeneous aliphatic rich kerogen and stiff ordered aromatic rich kerogen, evidenced by the increase in the stiffer component with maturity and correlated with 13C NMR spectrocopy. These findings enable increased realism in microscale geomechanical fracture tip propagation models and may allow direct comparison between Young's modulus and Rock‐Eval parameters.

Mechanobiological evaluation of prostate cancer metastasis to bone using an in vitro prostate cancer testbed

Prostate cancer exhibits a propensity to metastasize to the bone, which often leads to fatality. Bone metastasis is characterized by complex biochemical, morphological, pathophysiological, and genetic changes to cancer cells as they colonize at bone sites. In this study, we report the evaluation of MDA PCa2b prostate cancer cells' nanomechanical properties during the mesenchymal-to-epithelial transition (MET) and during disease progression at the metastatic site. Bone-mimetic tissue-engineered 3D nanoclay scaffolds have been used to create in vitro metastatic site for prostate cancer. A significant softening of the prostate cancer cells during MET and further softening as disease progression occurs at metastasis is also reported. The significant reduction in elastic modulus of prostate cancer cells during MET was attributed to actin reorganization and depolymerization. This study provides input towards direct nanomechanical measurements to evaluate the time evolution of cells' mechanical behavior in tumors at bone metastasis site.

The human Descemet's membrane and lens capsule: Protein composition and biomechanical properties

The Descemet's membrane (DM) and the lens capsule (LC) are two ocular basement membranes (BMs) that are essential in maintaining stability and structure of the cornea and lens. In this study, we investigated the proteomes and biomechanical properties of these two materials to uncover common and unique properties. We also screened for possible protein changes during diabetes. LC-MS/MS was used to determine the proteomes of both BMs. Biomechanical measurements were conducted by atomic force microscopy (AFM) in force spectroscopy mode, and complemented with immunofluorescence microscopy. Proteome analysis showed that all six existing collagen IV chains represent 70% of all LC-protein, and are thus the dominant components of the LC. The DM on the other hand is predominantly composed of a single protein, TGF-induced protein, which accounted for around 50% of all DM-protein. Four collagen IV-family members in DM accounted for only 10% of the DM protein. Unlike the retinal vascular BMs, the LC and DM do not undergo significant changes in their protein compositions during diabetes. Nanomechanical measurements showed that the endothelial/epithelial sides of both BMs are stiffer than their respective stromal/anterior-chamber sides, and both endothelial and stromal sides of the DM were stiffer than the epithelial and anterior-chamber sides of the LC. Long-term diabetes did not change the stiffness of the DM and LC. In summary, our analyses show that the protein composition and biomechanical properties of the DM and LC are different, i.e., the LC is softer than DM despite a significantly higher concentration of collagen IV family members. This finding is unexpected, as collagen IV members are presumed to be responsible for BM stiffness. Diabetes had no significant effect on the protein composition and the biomechanical properties of both the DM and LC.

Contact Stiffness Measurements with an Atomic Force Microscope

We propose a method for improving accuracy of nanomechanical measurements by an atomic force microscope. We describe the contact interaction of the cantilever with the sample using an analytic model taking into account different mechanisms of the cantilever probe operation (it can be clamped or can slide over the sample surface), the geometrical and mechanical characteristics of the sample and the cantilever, and their mutual arrangement. For the case of sliding, a filter is developed for correcting signals of contact stiffness and deformation measured on a sample with a developed relief. The application of the filter is illustrated by images obtained with an atomic force microscope in the visualization regime based on point-by-point recording of the forced quasi-static interaction of the cantilever probe with the sample.

Study of nanomechanical properties of thin films using in-situ “Push-to-Pull” method in the column of transmission electron microscope

The purpose of this study was to develop a method for determining the tensile strength of ion-plasma coatings during their nanodeformation in the column of a transmission electron microscope. The advanced oxidation-resistant coating in the Mo-Zr-Si-B system was selected as the object for mechanical testing. Coatings were deposited on alumina substrates by magnetron sputtering with hetero-phase cathode in system MoSi2-MoB-ZrB2 in argon environment. Coating’s characterization and testing were performed using XRD, SEM, EDS, GDOES, TEM, and nanoindentation. Nanomechanical study in TEM column was conducted in binding scheme using Push-to-Pull device and Picoindenter module on lamella prepared by FIB. Problems related to nanomechanical measurements and interpretation of the obtained dependences are discussed. Recommendations for the method of lamella preparing and parameters for testing were developed.

A nonlinear control strategy for robust tracking under exogenous vibrations for in-line nano-metrology

This paper proposes a novel, observer-based, nonlinear control strategy aimed at facilitating the pursuit of nanomechanical measurements within the noisy environments of industrial production lines. The investigation makes use of a laboratory-prototype emulating an architecture composed by a sample to be analyzed, and by a metrology platform whose task is to carry out in-line measurements, while the whole system is being affected by exogenous vibrations. The control objective is to lock the distance between the metrology platform and the sample, thereby allowing the pursuit of the measurement task. The proposed solution achieves robustness with respect to unknown plant parameters and exogenous disturbances by means of a combination of high-frequency and high-gain tools, and by relying on a novel “learning observer”. The proposed design is formally analyzed, and then experimentally validated by providing a comparative study with a PID-based control-strategy. The experimental results indicate, overall, a favorable performance of the proposed control algorithm over the PID counterpart.

Correction of height-fluctuation-induced systematic errors in polymers by AFM-based nanomechanical measurements

AFM-based nanomechanical measurements are powerful tools for the characterization of polymer composites. However, a flat surface of the samples is usually required, which restricts the wide applications of nanomechanical measurements. In this work, the height-fluctuation induced systematic errors were investigated taking polystyrene beads as the model sample. Corrections were further made based on the assumption that the components of force and deformation parallel to the sample surface can be approximately ignored. Results show the deviations of force and deformation due to height-fluctuations can be well corrected by the proposed method. Moreover, the reliability of the corrected force curves was further verified in the calculation of the mechanical properties. Young's moduli value without height-gradient dependency can be obtained by applying both Johson-Kendall-Roberts (JKR) model and Derjaguin-Muller-Toporov (DMT) model. The correction method proposed in this work can broaden the applications of AFM-based nanomechanical measurements on polymers without strict restrictions on the surface flatness.

Oxidation weakens interfaces in carbon nanotube reinforced titanium nanocomposites: An in situ electron microscopy nanomechanical study

The interfacial binding interactions in fiber–reinforced metal matrix nanocomposites (MMNC) are involved with sophisticated physico-chemical​ phenomena that are sensitive to their commonly encountered high-temperature processing and/or working environments. The resulting interfacial load transfer characteristics, which play a vital role in achieving the anticipated bulk mechanical properties enhancements, remain elusive. Here we investigate the effect of thermal processing on the interfacial strength of carbon nanotube (CNT) reinforced titanium (Ti) nanocomposites by conducting in situ nanomechanical single-nanotube pull-out measurements inside a high resolution scanning electron microscope. Our nanomechanical measurements reveal that thermal annealing at 400 °C for two hours results in a 40% decrease of the interfacial load-carrying capacity. The measurements were analyzed using a micromechanics shear-lag model, and the results show that the thermal annealing reduces the maximum interfacial shear strength by about 42% from about 231MPa to about 135 MPa. The observed weakening of the CNT–Ti interface caused by thermal annealing is attributed to the formation of newly grown titanium oxide on the CNT–Ti binding interface. The findings reported here are useful to better understand the impact of thermal processing on the reinforcing efficiency of nanotubes in metal matrices, which is essential to the design and manufacturing of nanotube-reinforced MMNC with superior high-temperature performance.

Corrosion effects on the granular nano mechanical properties of buried cast iron

Considerable research reported in literature shows that corrosive soil degrades the bulk mechanical properties of buried cast iron pipes due to cracks anddegradation of microstructure. The nanomechanical properties of the grains of cast iron pipes can also be affected by the corrosion before bulk mechanical properties. However, the influence of soil corrosivity on the nanomechanical properties at the granular level is remained unresolved to date. This paper addresses this gap and presents the nanomechanical measurements performed on the corroded cast iron specimens and the maximum degradation was quantified.Specimensafter 545 days of burial in corrosive soil conditions were tested by nanoindentation for determining the degradation of their nanomechanical properties. The analysis of the test results showed a significant reduction in the nano elastic and nano hardness of the grains of the cast iron due to the diffusion of hydrogen from the surrounding corrosive soil environments. The high corrosion rates were found proportional to inducing the maximum degradation of the nano elastic modulus of the grains. A relation for the prediction of maximum degradation of the nano elastic modulus of the grains as a function of corrosion rates, pH and moisture content of the clay soil was also developed. The finding of the current research is significant as it shows that apart from bulk mechanical properties, the nanomechanical properties of cast iron grains can be degraded by corrosive environments which in turn can affect the service life. Furthermore, understanding the mechanical science of the degradation of the grains can assist in manufacturing sustainable ferrous pipes resistive to corrosion soils.

One-Step Calibration of AFM in Liquid

Nanomechanical measurements of cells and single molecules with atomic force microscopy (AFM) require accurate calibration of two parameters: the spring constant of the cantilever (k) and the inverse of the optical lever sensitivity (InvOLS). The most established calibration approach in liquid consists in determining the InvOLS from force–distance curves on a stiff surface, k being calculated using the thermal spectrum (PSD) of the cantilever via the equipartition theorem. Recent works proposed using cantilevers with calibrated k and then determining the InvOLS from the PSD. These non-contact approaches improve the precision of nanomechanical measurements compared to conventional contact-based approaches. The Sader method or the recent global calibration initiative (GCI) are accurate approaches and do not require knowledge of the InvOLS to determine k, thus they would allow one-step calibration of AFM in liquid. However, both methods assume high quality factor cantilevers, not the case for most cantilevers in liquid. Here we assess the accuracy and precision of the Sader and GCI methods in liquid on two types of cantilevers with low Q-factor using two different PSD fitting models (SHO and Pirzer). We evaluate the two approaches using only the PSD in liquid to calibrate both k and the InvOLS. While both methods led to similar results, the GCI approach is less prone to systematic uncertainties and, using the SHO model, provides higher accuracy in k and the InvOLS. Therefore, the proposed SHO, GCI-based approach utilizing only the thermal spectrum in liquid is precise and accurate and allows one-step calibration of AFM.

The effect of finite sample thickness in scanning ion conductance microscopy stiffness measurements

Investigating the mechanical properties of soft biological samples on the single-cell level is of great interest as cell mechanics play a central role in many physiological processes in health and disease. Scanning ion conductance microscopy (SICM) is an emerging technique for measuring cell stiffness on the micro- and nanometer scale in a non-contact fashion. However, as SICM stiffness measurements are based on a localized deformation of the sample, they are affected by the thickness of the sample. We found experimentally and numerically that the apparent stiffness of a thin sample is overestimated. We present a straightforward correction method to account for this effect and derive a thickness-dependent, multiplicative correction factor, which we apply to SICM stiffness mapping of living cells. The correction method allows us to quantitatively measure the stiffness of thin samples with SICM and is, therefore, essential for the comprehensive application of SICM to nanomechanical measurements.

Long-Range Ordered Water Correlations between A–T/C–G Nucleotides

Summary The interactions between complementary base pairs are crucial to the helical duplex structure of DNA. Although base-base interactions have been widely reported, the study of long-range interactions in the base-pairing processes is still a major challenge in this field. Here, we first study the long-range interactions between the base pairs by atomic force microscopy-based single-molecule force spectroscopy (SMFS). The SMFS results of A–T/C–G imply that there are weak long-range interactions between them, which have a range of 15–25 nm. Raman spectroscopy results imply that these weak interactions can be attributed to multiplex hydrogen bond interaction of ordered water structure between A–T/C–G nucleotides. In addition, the theoretical calculations deduce that the ideal structure of these water molecules exhibits a specific helical structure. Our findings might open up a new understanding of biological assembly processes and provide helpful strategies for bio-nanotechnology.

Nanomechanical measurements shed light on solid-state battery degradation

Abstract

Quantitative mapping of high modulus materials at the nanoscale: comparative study between atomic force microscopy and nanoindentation.

Local mechanical properties of submicron features are of particular interest due to their influence on macroscopic material performance and behaviour. This study is focused on local nanomechanical measurements, based on the latest Atomic Force Microscopy (AFM) mode, where the peak force set point is finely controlled at each pixel. After probe calibration, we evaluate the impact of spring constant of two AFM hand-crafted natural full diamond tips with steel cantilevers, used for mapping. Based on the fast capture of the cantilever deflection at each pixel and real time force curve analysis in the elastic region, AFM local measured contact moduli mappings of the silica beads (>50GPa) incorporated in an epoxy resin matrix, are compared with those determined using classical instrumented nanoindentation tests. Our analyses show that with the two AFM probes, without local residual deformation, the high moduli of the silica beads measured with this advanced AFM mode are within the standard deviation of the values determined by classical nanoindentation. LAY DESCRIPTION: The knowledge of material properties at the nanometer scale is a key parameter for well understanding and determining the behavior of material at macroscopic scale. In this paper, we compare two methods (an advanced mode and a classical one) based on the analysis of probes in interaction with the surface of studied material. We focus on a latest developed mode for determining local mechanical properties with a very high spatial resolution. For the advanced mode, we also consider two different hand-crafted probes. Our analyses show that with the high spatial resolution advanced mode, local mechanical properties are well determined. We also highlight the impact of the properties of the used probes for this advanced mode. In a final step, the power of the presented investigation lies in the fact that it does not modify the topography of the surface.

Bioinspired All-Polyester Diblock Copolymers Made from Poly(pentadecalactone) and Poly(2-(2-hydroxyethoxy)benzoate): Synthesis and Polymer Film Properties.

The bioinspired diblock copolymers poly(pentadecalactone)-block-poly(2-(2-hydroxyethoxy)-benzoate) (PPDL-block-P2HEB) were synthesized from pentadecalactone and dihydro-5H-1,4-benzodioxepin-5-one (2,3-DHB). No transesterification between the blocks was observed. In a sequential approach, PPDL obtained by ring-opening polymerization (ROP) was used to initiate 2,3-DHB. Here, the molar mass Mn of the P2HEB block was limited. In a modular approach, end-functionalized PPDL and P2HEB were obtained separately by ROP with functional initiators, and connected by 1,3-dipolar Huisgen reaction ("click-chemistry"). Block copolymer compositions from 85:15 mass percent to 28:72 mass percent (PPDL:P2HEB) were synthesized, with Mn of from about 30,000-50,000 g mol-1. The structure of the block copolymer was confirmed by proton NMR, FTIR spectroscopy, and gel permeation chromatography. Morphological studies by atomic force microscopy (AFM) further confirmed the block copolymer structure, while quantitative nanomechanical AFM measurements revealed that the DMT moduli of the block copolymers ranged between 17.2 ± 1.8 MPa and 62.3 ± 5.7 MPa, i.e. between the values of the parent P2HEB and PPDL homopolymers (7.6 ± 1.4 MPa and 801 ± 42 MPa, respectively). Differential scanning calorimetry showed that the thermal properties of the homopolymers were retained by each of the copolymer blocks (melting temperature 90 °C, glass transition temperature 36 °C).

A MEMS nanoindenter with an integrated AFM cantilever gripper for nanomechanical characterization of compliant materials

This work presents the development of a MEMS nanoindenter that uses exchangeable AFM probes for quasi-static nanomechanical characterization of compliant and ultra-compliant materials. While the electrostatic micro-force transducer of the MEMS nanoindenter provides a maximum indentation depth up to 9.5 µm with a maximum output force of 600 µN, experimental investigations reveal that it can achieve a depth and force resolution better than 4 pm Hz−1/2 and 0.3 nN Hz−1/2, in air for f≥ 1 Hz. A passive AFM probe gripper is integrated into the MEMS nanoindenter, allowing the nanoindenter to utilize various AFM probes as an indenter for material testing. A proof-of-principle experimental setup has been built to investigate the performance of the MEMS nanoindenter prototype. In proof-of-principle experiments, the prototype with a clamped diamond AFM probe successfully identified an atomic step (∼0.31 nm) within a Si < 111 > ultraflat sample using the scanning probe microscopy mode. The nanomechanical measurement capability of the MEMS nanoindenter prototype has been verified by means of measurements of reference polymer samples using a silicon AFM probe and by means of measurements of the elastic properties of a PDMS sample using a spherical diamond-coated AFM probe. Owing to its compact and low-cost but high-resolution capacitive readout system, this MEMS nanoindenter head can be further applied for in-situ quantitative nanomechanical measurements in AFMs and SEMs.

Bioinspired All-Polyester Diblock Copolymers Made from Poly(pentadecalactone) and Poly(3-hydroxycinnamate): Synthesis and Polymer Film Properties.

A bioinspired diblock copolymer was synthesized from pentadecalactone and 3-hydroxy cinnamic acid. Poly(pentadecalactone) (PPDL) with a molar mass of up to 43,000 g mol-1 was obtained by ring-opening polymerization initiated propargyl alcohol. Poly(3-hydroxy cinnamate) (P3HCA) was obtained by polycondensation and end-functionalized with 3-azido propanol. The two functionalized homopolymers were connected via 1,3-dipolar Huisgen addition to yield the block copolymer PPDL-triazole-P3HCA. The structure the block copolymer was confirmed by proton NMR, FTIR spectroscopy and GPC. By analyzing the morphology of polymer films made from the homopolymers, from a 1:1 homopolymer blend, and from the PPDL-triazole-P3HCA block copolymer, clearly distinct micro- and nanostructures were revealed. Quantitative nanomechanical measurements revealed that the block copolymer PPDL-triazole-P3HCA had a DMT modulus of 22.3 ± 2.7 MPa, which was lower than that of the PPDL homopolymer (801 ± 42 MPa), yet significantly higher than that of the P3HCA homopolymer (1.77 ± 0.63 MPa). Thermal analytics showed that the melting point of PPDL-triazole-P3HCA was similar to PPDL (89-90 °C), while it had a glass transition was similar to P3HCA (123-124 °C). Thus, the semicrystalline, potentially degradable all-polyester block copolymer PPDL-triazole-P3HCA combines the thermal properties of either homopolymer, and has an intermediate elastic modulus.

Investigation of the Dissociation Mechanism of Single-Walled Carbon Nanotube on Mature Amyloid-β Fibrils at Single Nanotube Level.

Amyloid fibrils originating from the fibrillogenesis of misfolded amyloid proteins are associated with the pathogenesis of many neurodegenerative diseases, such as Alzheimer's, Parkinson's, and Huntington's diseases. Carbon nanotubes have been extensively applied in our life and industry due to their unique chemical and physical properties. Nonetheless, the details between carbon nanotubes and mature amyloid fibrils remain elusive. In this study, we explored the interplay between single-walled carbon nanotubes (SWCNTs) and preformed amyloid-β (Aβ) fibrils by atomic force microscopy at the single SWCNT level, together with ThT fluorescence, cellular viability assays, infrared spectroscopy, and molecular dynamics (MD) simulations. The results demonstrated that SWCNTs could partially destroy the preformed Aβ fibrils and form the Aβ-surrounded-SWCNTs conjugates, as well as reduce the β-sheet structures. Peak force quantitative nanomechanical measurements revealed that the conjugates have lower Young's modulus than fibrils. Furthermore, our MD simulation demonstrated that the dissociation ability was dependent on the binding sites of Aβ fibrils. Overall, this study provides an insight into the dissociation mechanism between SWCNT and Aβ fibrils, which could be beneficial for the study of bionanomaterials and the development of other potential drug candidates for amyloidosis.

Coating and Stabilization of Liposomes by Clathrin-Inspired DNA Self-Assembly.

The self-assembly of the protein clathrin on biological membranes facilitates essential processes of endocytosis and has provided a source of inspiration for materials design by the highly ordered structural appearance. By mimicking the architecture of the protein building blocks and clathrin self-assemblies to coat liposomes with biomaterials, advanced hybrid carriers can be derived. Here, we present a method for fabricating DNA-coated liposomes by hydrophobically anchoring and subsequently connecting DNA-based triskelion structures on the liposome surface inspired by the assembly of the protein clathrin. Dynamic light scattering, ζ-potential, confocal microscopy, and cryo-electron microscopy measurements independently demonstrate successful DNA coating. Nanomechanical measurements conducted with atomic force microscopy show that the DNA coating enhances the mechanical stability of the liposomes relative to uncoated ones. Furthermore, we provide the possibility to reverse the coating process by triggering the disassembly of the DNA coats through a toehold-mediated displacement reaction. Our results describe a straightforward, versatile, and reversible approach for coating and stabilizing lipid vesicles through the assembly of rationally designed DNA structures. This method has potential for further development toward the ordered arrangement of tailored functionalities on the surface of liposomes and for applications as hybrid nanocarriers.

Beyond the paradigm of nanomechanical measurements on cells using AFM: an automated methodology to rapidly analyse thousands of cells

This paper reports a methodology which includes an algorithm able to move an AFM tip onto a single cell and through several cells combined with a smart strategy of cell immobilization.