Nanomechanical Mapping Atomic Force Microscopy Research Articles

Electron Tomography and Machine Learning for Understanding the Highly Ordered Structure of Leafhopper Brochosomes.

Insects known as leafhoppers (Hemiptera: Cicadellidae) produce hierarchically structured nanoparticles known as brochosomes that are exuded and applied to the insect cuticle, thereby providing camouflage and anti-wetting properties to aid insect survival. Although the physical properties of brochosomes are thought to depend on the leafhopper species, the structure-function relationships governing brochosome behavior are not fully understood. Brochosomes have complex hierarchical structures and morphological heterogeneity across species, due to which a multimodal characterization approach is required to effectively elucidate their nanoscale structure and properties. In this work, we study the structural and mechanical properties of brochosomes using a combination of atomic force microscopy (AFM), electron microscopy (EM), electron tomography, and machine learning (ML)-based quantification of large and complex scanning electron microscopy (SEM) image data sets. This suite of techniques allows for the characterization of internal and external brochosome structures, and ML-based image analysis methods of large data sets reveal correlations in the structure across several leafhopper species. Our results show that brochosomes are relatively rigid hollow spheres with characteristic dimensions and morphologies that depend on leafhopper species. Nanomechanical mapping AFM is used to determine a characteristic compression modulus for brochosomes on the order of 1-3 GPa, which is consistent with crystalline proteins. Overall, this work provides an improved understanding of the structural and mechanical properties of leafhopper brochosomes using a new set of ML-based image classification tools that can be broadly applied to nanostructured biological materials.

Electron-induced reactive processing of polyamide 6/polypropylene blends: Morphology and properties

Electron-induced reactive processing (EIReP) recently has appeared as an advanced processing technology to modify several polymer compounds at melt state by its spatial and temporal precise energy input. In the present work, an attempt was made to prepare a compatible blend from polar polyamide 6 (PA6) and non-polar polypropylene (PP) using EIReP without any chemical crosslinking and chemical additives. EIReP modified blends were prepared at different doses (5, 10 and 20 kGy) and dose per revolutions (3, 6 and 12 kGy/rev) while keeping constant the values of mass ratio (PA6/PP 50/50 w/w), electron energy (1.5 MeV), rotor speed (60 rpm) and temperature (230 °C). EIReP process parameters-morphology-property relationship of this blend was studied. Interestingly, co-continuous morphology of the blend was converted to droplet-matrix morphology after EIReP whether PA6 was continuous phase. Influence of dose and dose per revolution on the DMT modulus (Derjaguin-Muller-Toporov) at different phases of the blends was also measured and analyzed using advanced PeakForce Quantitative Nanomechanical Mapping atomic force microscopy (PF QNM AFM) technique. Improved nano- and macroscopic properties of EIReP modified blends were originated from the properties of the continuous matrix phase, electron-induced branching and also from the reduction of domain size of PP phase with increased dose.

In-situ evaluation of dye adsorption on TiO2using QCM

We measured the adsorption characteristics of two organic dyes; triphenylamine-cyanoacrylic acid (TPA-C) and phenoxazine (MP13), on TiO2 , directly in a solution based on quartz crystal microbalance (QCM). Monitoring the adsorbed amount as a function of dye concentration and during rinsing allows determination of the equilibrium constant and distinction between chemisorbed and physisorbed dye. The measured equilibrium constants are 0.8 mM-1 for TPA-C and 2.4 mM-1 for MP13. X-ray photoelectron spectroscopy was used to compare dried chemisorbed layers of TPA-C prepared in solution with TPA-C layers prepared via vacuum sublimation; the two preparation methods render similar spectra except a small contribution of water residues (OH) on the solution prepared samples. Quantitative Nanomechanical Mapping Atomic Force Microscopy (QNM-AFM) shows that physisorbed TPA-C layers are easily removed by scanning the tip across the surface. Although not obvious in height images, adhesion images clearly demonstrate removal of the dye.

Quantitative Nanomechanical Properties of Multilayer Films Made of Polysaccharides through Spray Assisted Layer-by-Layer Assembly.

Nanomechanical properties of alginate/chitosan (Alg/Chi) multilayer films, obtained through spray assisted layer-by-layer assembly, were studied by means of PeakForce quantitative nanomechanical mapping atomic force microscopy (PF-QNM AFM). Prepared at two different alginate concentrations (1.0 and 2.5 mg/mL) and a fixed chitosan concentration (1.0 mg/mL), Alg/Chi films have an exponential growth in thickness with a transition to a linear growth toward a plateau by increasing the number of deposited bilayers. Height, elastic modulus, deformation, and adhesion maps were simultaneously recorded depending on the number of deposited bilayers. The elastic modulus of Alg/Chi films was found to be related to the mechanism of growth in contrast to the adhesion and deformation. A comparison of the nanomechanical properties obtained for non-cross-linked and thermally cross-linked Alg/Chi films revealed an increase of the elastic modulus after cross-linking regardless alginate concentration. The incorporation of iron oxide nanoparticles (NPs), during the spray preparation of the films, gave rise to nanocomposite Alg/Chi films with increased elastic moduli with the number of incorporated NPs layers. Deformation maps of the films strongly suggested the presence of empty spaces associated with the method of preparation. Finally, adhesion measurements point out to a significant role of NPs on the increase of the adhesion values found for nanocomposite films.

Simultaneous Advanced Microscopies for Live Cell Signaling Dynamics Investigations

We present a new type of combined microscopy for the life sciences based on the integration of differential spinning disk fluorescence optical sectioning microscopy and nanomechanical mapping Atomic Force Microscopy (AFM).[1] Our hardware platform creates the opportunity for simultaneous acquisition of membrane receptor recognition maps and fluorescence optical sectioning images of live cells, providing new experimental capabilities in cell signaling investigations.Simultaneous spatio-temporal generation of AFM and fluorescence microscopy data is made possible through time-independent illumination at low light intensities of the AFM cantilever that strongly reduces the interaction of AFM cantilever motion with fluorescence excitation light as compared to existing hardware integration platforms based on confocal laser scanning microscopy and AFM. Namely, fluorescence excitation light has the capability to induced cantilever heating and subsequent sample heating through heat conduction. We identify several system specific noise-sources that can interfere with live cell investigations and describe solutions to mitigate them.[1] Miranda, A., Martins, M. & De Beule, P. A. A. Simultaneous differential spinning disk fluorescence optical sectioning microscopy and nanomechanical mapping atomic force microscopy. Rev. Sci. Instrum. 86, 093705 (2015).

Application of atomic force microscopy for investigation of Na(+),K(+)-ATPase signal-transducing function.

The Young's modulus of 10-12-day-old chick embryos' sensory neurons cultivated in dissociated cell culture was measured using a PeakForce Quantitative Nanomechanical Mapping atomic force microscopy. The native cells were tested in control experiments and after application of ouabain. At low "endogenous" concentration of 10⁻¹⁰ M, ouabain tended to increase the rigidity of sensory neurons. We hypothesize that this trend resulted from activation of Na⁺,K⁺-ATPase signal-transducing function.