DOI: 10.5061/dryad.556mh3j
title: Data from: Automated analysis of soft hydrogel microindentation: impact of various indentation parameters on the measurement of Young's modulus

description: Measurements of Young's moduli are mostly evaluated using strong
 assumptions, such as sample homogeneity and isotropy. At the same time,
 descriptions of measurement parameters often lack detailed specifications.
 Many of these assumptions are, for soft hydrogels especially, not
 completely valid and the complexity of hydrogel microindentation demands
 more sophisticated experimental procedures in order to describe their
 elastic properties more accurately. We created an algorithm that automates
 indentation data analysis as a basis for the evaluation of large data sets
 with consideration of the influence of indentation depth on the measured
 Young's modulus. The algorithm automatically determines the
 Young's modulus in indentation regions where it becomes independent
 of the indentation depth and furthermore minimizes the error from fitting
 an elastic model to the data. This approach is independent of the chosen
 elastic fitting model and indentation device. With this, we are able to
 evaluate large amounts of indentation curves recorded on many different
 sample positions and can therefore apply statistical methods to overcome
 deviations due to sample inhomogeneities. To prove the applicability of
 our algorithm, we carried out a systematic analysis of how the indentation
 speed, indenter size and sample thickness affect the determination of
 Young's modulus from atomic force microscope (AFM) indentation curves
 on polyacrylamide (PAAm) samples. We chose the Hertz model as the elastic
 fitting model for this proof of principle of our algorithm and found that
 all of these parameters influence the measured Young's moduli to a
 certain extent. Hence, it is essential to clearly state the experimental
 parameters used in micro indentation experiments to ensure reproducibility
 and comparability of data.
description: Raw data for figure
 1The
 folder contains the force-distance curve used for figure
 1.Fig1_principle.zipFig2_beadsizeThe folder contains the force-distance curves used for figure 2 divided into subfolders for each beadsize.Raw data for figure 3The folder contains the force-distance curves used for figure 3 divided into subfolders for each thickness.Fig3_thickness.zipRaw data for figure 4_0.1µm/sThe folder contains the force-distance curves used for figure 4 (speed of 0.1 µm/s).Fig4_indentation_speed_0.1µms.zipRaw data for figure 4_1µm/sThe folder contains the force-distance curves used for figure 4 (speed of 1 µm/s).Fig4_indentation_speed_1µms.zipRaw data for figure 4_5µm/sThe folder contains the force-distance curves used for figure 4 (speed of 5 µm/s).Fig4_indentation_speed_5µms.zipRaw data for figure 4_10µm/sThe folder contains the force-distance curves used for figure 4 (speed of 10 µm/s).Fig4_indentation_speed_10µms.zipRaw data for figure 4_20µm/sThe folder contains the force-distance curves used for figure 4 (speed of 20 µm/s).Fig4_indentation_speed_20µms.zipRaw data for figure 4_40µm/sThe folder contains the force-distance curves used for figure 4 (speed of 40 µm/s).Fig4_indentation_speed_40µms.zipRaw data for figure 4_100µm/sThe folder contains the force-distance curves used for figure 4 (speed of 100 µm/s).Fig4_indentation_speed_100µms.zipRaw data for figure 5The data used for figure 5 is the same as for figure 4 (speed of 1 µm/s).Fig5_positions.zipData used for the supporting informationThe folder contains the data used for the supporting information including the Matlab algorithms. The folder is divided into subfolders for each SI figure.supporting information.zip