Analysis of compression data from four representative hydrogel samples.

<p>All data shown is 4 mg/ml, pH 8.4, 37°C. a) Identification of contact position, marked by a filled circle. b) Robust loess smoothing. c) Linear regression of smoothed data from 5–15% strain. Sample 1 (green) is discarded after step (a) because the sample thickness, determined from the contact position, is 6.9% (585 μm) less than the nominal thickness. Sample 2 (blue) is discarded after step (c) because E = -8617 Pa < 0. Sample 3 (red) is also discarded after step (c) because the regression R² = 0.065 < 0.5. Sample 4 (black) is considered valid and returns a compression modulus of 3320 Pa which contributes to the mean compression modulus calculated for this fabrication condition.