Designing superlubricious hydrogels from spontaneous peroxidation gradients

Hydrogels are hydrated three-dimensional networks of hydrophilic polymers that are commonly used in the biomedical industry due to their mechanical and structural tunability, biocompatibility, and similar water content to biological tissues. The surface structure of hydrogels polymerized through free-radical polymerization can be modified by controlling environmental oxygen concentrations, leading to the formation of a polymer concentration gradient. In this work, 17.5 wt % polyacrylamide hydrogels are polymerized in low (0.01 mol % O2) and high (20 mol % O2) oxygen environments, and their mechanical and tribological properties are characterized through microindentation, nanoindentation, and tribological sliding experiments. Without significantly reducing the elastic modulus of the hydrogel (E* ≈ 200 kPa), we demonstrate an order of magnitude reduction in friction coefficient (from μ = 0.021 ± 0.006 to μ = 0.002 ± 0.001) by adjusting polymerization conditions (e.g., oxygen concentration..., Microindentations and friction measurements were conducted using a custom-built linear reciprocating microtribometer. 
Nanoindentations were conducted using an atomic force microscope (Asylum MFP-3D Bio).
Data was analyzed using custom MATLAB codes., All files are in open-source formats (.csv, .txt).  , Data from peer-reviewed article:

Title: Designing Superlubricious Hydrogels from Spontaneous Peroxidation Gradients
Article: ACS Applied Materials and Interfaces
Authors: Allison L. Chau\*, Chelsea E. R. Edwards\*, Matthew E. Helgeson, Angela A. Pitenis
\*co-first author
Corresponding author: Angela Pitenis, [e-mail]

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File List
A) Fig03b.csv
B) Fig03c.csv
C) Fig03d.csv
D) Fig04a.csv
E) Fig04b.csv
F) Fig05a.csv
G) Fig05b\_FigS14a.csv
H) Fig05c\_FigS14b.csv
I) Fig06a\_FigS11.csv
J) Fig06b\_FigS12.csv
K) FigS01.csv
L) FigS04.csv
M) FigS05a.csv
N) FigS05b.csv
O) FigS06.csv
P) FigS07a.csv
Q) FigS07b.csv
R) FigS08a.csv
S) FigS08b.csv
T) FigS09.csv
U) FigS10a.csv
V) FigS10b.csv
W) FigS13.csv
X) FigS15.csv
Y) FigS16.csv
Z) FigS17.csv
AA) TableS07\_E\_mu\_lit\_value\_compilation
AB) Friction\_Data\_Compilation.csv
AC) Modulus\_Data\_Compilation.csv

FIGURE 3: microtribometer
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A) Fig03b.csv: representative microtribometer indentation curves

* row 1: x and y axis, corresponding...