Space-resolved quantitative mechanical measurements of soft and supersoft materials by atomic force microscopy

Abstract

Atomic force microscopy (AFM) has proven to be a valuable instrument to characterize quantitatively the mechanical and morphological properties of soft materials. For medium and hard samples (E41 MPa), the nanomechanical accuracy of AFM is well established and ascertained. However, for soft samples, the experimental setup and data analysis for AFM are not yet firmly established. A calibration obtained for homogeneous samples with a Young's modulus ranging from 100 Pa to a few kPa will prove its usefulness for nanomechanical AFM investigations of soft biological specimens, such as living cells and extracellular matrices. For this purpose, poly(N-isopropylacrylamide) (PNIPAM) hydrogels were synthesized in different methanol − water mixtures to produce a series of homogeneous samples with finely tunable mechanical properties. These samples allowed the comparison and validation of AFM force spectroscopy results using macroscopic and rheological techniques. In AFM measurements, the geometry of the indenter is fundamental to the model used for data interpretation; therefore, experiments were carried out using spherical micrometric and standard pyramidal sharp probes. Moreover, a PNIPAM gel embedded with hard microspheres was analyzed, which showed the capability of AFM for measuring the local mechanical properties of heterogeneous samples.

Bacterial Adhesion Is Affected by the Thickness and Stiffness of Poly(ethylene glycol) Hydrogels

“…AFM determined that the thin-stiff, medium-stiff, and thick-stiff hydrogels had a statistically equivalent Young’s modulus values of 950 ± 90 kPa, 1000 ± 90 kPa, and 11000 ± 90 kPa, respectively, which were consistent with the literature. 27,43 There was no statistical differences between the two techniques; the Young’s moduli of soft and intermediate hydrogels at all thicknesses (thin, medium, thick, and bulk) was the same. While the AFM measurements were consistent within the stiff hydrogels (thin, medium, and thick), their Young’s moduli were lower than that acquired using rheology.…”

Investigation of the Chemical Residuals on the Fused Silica during Chemical Mechanical Polishing

“…We conducted experiments with 64*64 lateral resolution (4096 points) using a pyramid probe with tip radius 20 nm were obtained for each FC. A series of 2–3 FV measurements were carried in various macroscopic positions to enhance the statistical reliability of the experiments …”

“…A series of 2-3 FV measurements were carried in various macroscopic positions to enhance the statistical reliability of the experiments. [17] The new born chemical residuals on fused silica surface were detected by a Fourier transform infrared (FTIR) spectrometer using an ART FTIR spectrometer HYPARION from Bruker, Germany at room temperature. Spectra were recorded from 600 to 4000cm À 1 using a DlaTGS detector.…”

Imidazolium-Based Ionic Liquids Affect Morphology and Rigidity of Living Cells: an Atomic Force Microscopy Study

“…In order to consider the most external layers of the cell, For each cell condition, (exact number N of cells used for statistic is shown in Table 1), the mean Young's modulus value E, and its associated effective errors (standard deviation  and standard deviation of the mean E) have been calculated, following the procedure described in details in Ref. 61,72 The results are therefore presented as E ±  (± E). Young's modulus values are typically represented in a semilog10 scale.…”