Figure 1.
Synthesis of the silicone elastomer matrix.
The PDMS is cross-linked via Pt-catalyzed hydrosilylation.
Figure 2.
Elastic moduli of the elastomers in the absence of magnetic field as measured by different methods.
All indentation data are average values over the entire surface and the indentation depth is 200 µm. (A) Unfilled PDMS matrix; (B) MAE filled with 30 vol. % of CIP. Values represent the average of five separate experiments. Error bars show the standard deviations from the mean.
Figure 3.
Concepts for controlling the MAE substratum in cell experiments.
(A) Schematic of the static device for generating different EIT on the MAE surface. (B) Schematic of the dynamic device for introducing displacement field and strain on the surface of the MAE substratum.
Figure 4.
Rheological characterization of the MAE sample M2.
(A) Shear modulus |G| = |G′+jG′′| versus shear strain γ (measurement parameters: amplitude sweep, f = 1 Hz, = 25°C). (B) Complex shear modulus G* versus magnetic flux density Bz (measurement parameters: f = 1 Hz, γ = 1%,
= 25°C, FN = 0.1 N).
Figure 5.
Static device for controlling the indentation modulus EIT on the MAE surface (sample M2).
(A) Schematic diagram of the device in combination with the well24 cell carrier in a cut illustration. (B) Photograph of the assembled prototype. (C) Dimensions of the device and the positions of the magnetic circuits (top view). (D) EIT in the geometrical center of the MAE surface. EIT value in the absence of magnetic field (M2 baseline) is shown for comparison. Values represent the average of five separate experiments. Error bars show the standard deviations from the mean. (D) Conditions for the magnetic field: values B1≈20 mT and B2≈35 mT (in the geometrical center of MAE surface), Hall probe HMNTAN-DQ 02-TH).
Figure 6.
Inhomogeneous distribution of EIT over the MAE surface (sample M2).
(A) Areas with different levels of EIT on the MAE surface. (B) Average values of EIT in different areas (rows 1/2 and 3/4). Values represent the average of three separate experiments. Error bars show the range of values measured.
Figure 7.
Deformation of the MAE substratum (sample M2) with applied time varying magnetic field.
(A) Distribution of engineering strain εxx = Δlx/lx at the MAE surface. (B) Average maximum strain εxx in different areas. (C) Distribution of the displacement vector over the MAE surface. (D) Average maximum displacement Δlx in different areas. Values represent the average of three separate experiments. Error bars show the range of values measured. Experiment conditions for the magnetic field: Amplitude
= 10 mT (in the geometrical center of the probe), f = 1 Hz, Hall probe HMNA-DQ02-TH. Experiment condition for the recording: Zeiss AxioScope A1, camera AVT Stingray F-125B, frame rate 18 frames/s.
Figure 8.
Elasticity-dependent protein expression on soft PDMS (U1–U3) and MAE (M1–M3) substrata in the absence of magnetic field.
(A) Western Blot and (B) immunofluorescence analysis show decreased expression of the myofibroblast marker α-smooth muscle actin with decreasing E-modulus of the substratum. “G” refers to glass in (A).
Figure 9.
Effects of magnetic field-induced change in substratum properties.
(A) Mean fibroblast cell area 60 min after plating increases with substratum E-modulus. (B) Transcription of the muscle satellite cell marker PAX-7 in human mesenchymal stem cells decreases with increasing substratum E-modulus. Triplicate mean ±SEM. Asterisks indicate significance of difference from controls **p<0.01, *p<0.05.
Figure 10.
MAE movement (f = 1 Hz) by varying magnetic field strength is well tolerated by attached human dermal fibroblasts.
(A) Composite image of (B, red and C, green) depicting displacement extremes. (D) Cell movement in 7 h: 56 min. Composite image of first (E, red in D) and last frame (F, green in D) of a time lapse series with 15 frames/h.