Abstract
Programmed, reshaping hydrogel architectures were fabricated from sugar/hydrogel inks via a three-dimensional printing method involving a stimuli-responsive polymer. We developed a new hydrogel ink composed of monomers (acrylamide [AAm]) and N-isopropylacrylamide [NIPAAm]), and sugar (mixture of glucose and sucrose) as a pore-generator, enabling to improve printability by increasing the ink’s viscoelastic properties and induce the formation of macropores in the hydrogel architectures. This study demonstrated that creating macropores in such architectures enables rapid responses to stimuli that can facilitate four-dimensional printing. We printed bilayer structures from monomer inks to which we had added sugar, and we exposed them to processes that cross-linked the monomers and leached out the sugar to create macropores. In comparison with a conventional poly(N-isopropylacrylamide) hydrogel, the macroporous hydrogels prepared using polymerization in the presence of a high concentration of sugar showed higher swelling ratios and exhibited much faster response rates to temperature changes. We used rheometry and scanning electron microscopy to characterize the properties of these inks and hydrogels. The results suggest that this method may provide a readily available route to the rapid design and fabrication of shape-morphing hydrogel architectures with potential application in soft robotics, hydrogel actuators, and tissue engineering.
Highlights
Current research in 4D printing mainly focuses on (1) the development of novel materials that are able to respond to various stimuli[17], and (2) the implementation of various shape memory geometries through physical designs for more applications[18]
We developed a new hydrogel ink composed of monomers and N-isopropylacrylamide [NIPAAm]), a cross-linker, a photoinitiator, sodium alginate, sugar, and water as a solvent
A bilayer containing AAm and NIPAAm was printed from the new ink and immediately UV-photopolymerized with an initiator to synthesize poly(N-isopropylacrylamide) (PNIPAAm) and polyacrylamide (PAAm) hydrogels and to form chemical bonds between the bilayer
Summary
Current research in 4D printing mainly focuses on (1) the development of novel materials that are able to respond to various stimuli[17], and (2) the implementation of various shape memory geometries through physical designs for more applications[18]. Structures printed with existing hydrogel inks have soft and fragile mechanical properties, requiring them to be strengthened via the incorporation of an extra supporting layer (e.g., polycaprolactone), additives (e.g., nanoclay or nanocelluose), or interpenetrating polymer networks (IPNs) to increase viscoelasticity[1,2,12,28]. Single component hydrogels, such as native PNIPAAm hydrogel[29] and alginate hydrogel[30] have been reported, and they are physically weak, being in the range of ~10 kPa. By incorporating alginate hydrogel into a PNIPAAm hydrogel matrix, the mechanical strength can be increased by orders of magnitude; for example, the tensile strengths for alginate/PNIPAAm29 and alginate/PAAm31 hydrogels increased to 120 kPa and[143] kPa, respectively. We hypothesized that the addition of sugar to the ink would enable us to (1) improve printability by increasing the ink’s viscoelastic properties and (2) induce the formation of macropores to enable large deformation and fast responses in the printed structures
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
