Design and preparation of 3D printing intelligent poly N,N-dimethylacrylamide hydrogel actuators

Abstract

<jats:title>Abstract</jats:title><jats:p>The intelligent poly <jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>-dimethylacrylamide hydrogel material system with high mechanical strength and the 3D printable property was prepared via <jats:italic>in situ</jats:italic> free radical polymerization under vacuum successfully. With the increase in nanofibrillated cellulose (NFC) content, stress and strain of hydrogels increased gradually. As the effective reinforcement, NFC enhanced the crosslinking density, which realized the controllable regulation of rheology behaviors including viscosity, storage modulus, and loss modulus of hydrogels. Combined with the swelling rate and the existence of the gel–sol transition point, a hydrogel with 10 mg/mL NFC was treated as the 3D printing ink of hydrogel actuators. Variation of printing parameters significantly affected self-driven deformations. The hydrogel actuators with 90°/0° and 45°/135° configurations owned bending and spiral deformations, respectively. Actuators with a larger length–width ratio owned a lower pitch value. The precise anisotropic swelling property of the printed bilayer structure was the self-driven deformation mechanism of hydrogel actuators, which provided material candidates for the preparation of soft robots and actuators.</jats:p>

Polymeric Microneedle Arrays with Glucose-Sensing Dynamic-Covalent Bonding for Insulin Delivery

“…Accordingly, the Boc NEA block consisted of ∼17% of the synthesized polymer, effectively matching the target of 16.67% established by the monomer feed ratio. DMAA was selected as the majority component due to the excellent solubility of polyDMAA in water and the high mechanical strength of the polymer arising from the self-hydrogen bonding capacity DMAA side chains. − Mechanical properties were an important consideration when designing microneedles to be prepared using dynamic-covalent crosslinking so as to ensure these had the requisite rigidity and strength to penetrate the dermal layer. The introduction of Boc NEA provides a protected amine side chain on the polymer for subsequent post-synthetic modification, thereby dictating the crosslink density of the resulting network.…”

Rheology of Gels and Yielding Liquids

“…The authors [ 192 ] took the crossover point as the moment of sol–gel transition at the lowest frequency used, where G ′ and G ″ were proportional to ω 2 and ω, respectively, although the experimental data showing the dependence of this moment on the frequency were also presented. This is a quite common technique for determining gel time at various temperatures [ 66 , 192 , 193 , 194 , 195 ], although (as stated above) this method does not correspond to the real transition and should be considered conditional for usage in technological applications.…”

Vat Photopolymerization of Nanocellulose-Reinforced Vegetable Oil-Based Resins: Synergy in Morphology and Functionalization

“…15 According to Zhou et al, adding nano-fibrilated cellulose (NFC) to N,N-dimethylacrylamide-based hydrogels increased compressive failure strain by 26% and failure stress by 47%. 16 Likewise, Wang et al reported a drastic improvement in the mechanical properties of VO-based nanocrystalline cellulose (NCC) composites, with up to 700% and 1500% increases in tensile strength and modulus, respectively, but the authors used relatively high NCC loadings (up to 50 wt %). 17 Vidakis et al incorporated 0.5−2.0 wt % NFC into medical grade resin, and after vat photopolymerization, a high-mechanical performance print showed a 114% increase in tensile strength and a 150% increase in tensile modulus with diminished strain value.…”

“…Due to its excellent mechanical properties and natural prevalence, nanocellulose represents an attractive option . According to Zhou et al, adding nanofibrilated cellulose (NFC) to N , N -dimethylacrylamide-based hydrogels increased compressive failure strain by 26% and failure stress by 47% . Likewise, Wang et al reported a drastic improvement in the mechanical properties of VO-based nanocrystalline cellulose (NCC) composites, with up to 700% and 1500% increases in tensile strength and modulus, respectively, but the authors used relatively high NCC loadings (up to 50 wt %) .…”