Thermal response of multi-layer UV crosslinked PEGDA hydrogels

Nanoindentation Response of 3D Printed PEGDA Hydrogels in a Hydrated Environment

“…1 H NMR analysis support the argument that an increased UV light dosage increases cross-linking in the 3D printed PEGDA structures. As previously reported, monolithic PEGDA hydrogel samples made in the absence of a QY photoabsorber had the highest degree of cross-linking, whereas multilayered PEGDA hydrogels, multi-150 μm-3 s and multi-20 μm-3 s, with 9 and 1.8 mg/mL of QY photoabsorber concentrations had lower cross-linking, respectively. In mono-1200 μm-3 s stored in D 2 O for 24 h and consequently analyzed by 1 H NMR spectroscopy, evidence of traces of protons of −CH 2 CH 2 O– and CH 2  CH– groups centered at 3.80 and 6.25 ppm, respectively, was observed, confirming that the amount of unreacted prepolymers was negligible albeit not zero (Figure b).…”

“…In terms of the relationship between E and the layer thickness, the nanoindentation measurements on 3D printed hydrogels do not agree with the typical “the thinner the stronger” behavior. The negative correlation between E and the number of layers may originate from the change in the QY photoabsorber concentration in the prepolymer solution (Figure b), which was 0 mg/mL for the mono-1200 μm-3 s, 1.8 mg/mL for multi-150 μm-3 s, and 9 mg/mL for the multi-20 μm-3 s. A previous study showed that the variation in the QY photoabsorber concentration affects the degree of cross-linking in the formed layers . A constant QY photoabsorber concentration at 1.8 mg/mL was therefore used to eliminate the effect of QY and to allow the assumption of the same degree of cross-linking for the multi-300 μm-3 s, multi-150 μm-3 s, and multi-37.5 μm-3 s samples (Figure d).…”

“…In a previous study, the thermal response of 3D multilayered PEGDA hydrogels was investigated through a gravimetric method for samples stored in deionized water (DIW) . As 3D PEGDA hydrogels are intended for use in biological applications, their thermal response was expanded to include the hydrogel stored in cell culture medium (CCM) baths at 8, 20, and 37 °C.…”

“…The normalized weight fraction (NWF) was used to calculate the weight change using eq NWF = M normals / M 0 where ( M s ) and ( M 0 ) are the weight of the hydrogel at time t and weight of the hydrogel immediately after fabrication, i.e., time 0, respectively.…”

“…15 − 18 A projection lithography 3D printing technique enables rapid fabrication of photo-cross-linkable hydrogels with complex geometrical features, e.g., high aspect ratio pillars, lattices, or overhangs, and an alteration in associated mechanical characteristics. 19 , 20 This makes it critical to fully understand the surface mechanical properties of hydrogels for designing and engineering smarter bioscaffold structures expanding functionality. 21 − 23 A previous study has demonstrated the contractile force measurement of muscle tissue strips using 3D printed poly(ethylene glycol) diacrylate (PEGDA) hydrogel cantilevers, 24 underpinned by the ability to engineer the elastic modulus and selective adhesion at the interface between the tissue strip and the PEGDA cantilever.…”