RESEARCHERS at Princeton University have discovered a way to make hydrogel in an instant and chemical-free way by forcing polymer fibres and water through a syringe.
Hydrogels are porous, soft and biocompatible, and as such are becoming more and more widely used, including for artificial tissue engineering, sustained drug delivery, surgical adhesives and 3D bioprinting. Creating them generally involves particular chemical reactions and interactions. However, the new hydrogel created by mechanical and aerospace engineering professor Howard Stone and his team is formed simply through shear thickening forces created as the polymer fibres and water are forced through a syringe nozzle. Stone and the team say that the new hydrogel could lead to a new class of injectable hydrogels for tasks such as plugging and treating wounds.
The fibres are made from poly(ethylene glycol) diacrylate (PEG-DA), a non-toxic, flexible, biocompatible polymer, and are 35 µm in diameter and 12 mm long. In water, the fibres are free-flowing and untangled. When forced through a syringe, the liquid suspension emerges as a gel.
To study the phenomenon, the Princeton team used a rheometer, a device which measures how fluids respond to applied forces. The liquid flows into a gap between two plates, the bottom of which is fixed, while the top one moves. They found that under these forces, the fibres bent, looped, and interlocked and tangled together. Water was trapped within the fibres, creating the hydrogel. The precise properties of the hydrogel can be altered by changing the diameter and length of the microfibres.
“Studying the flow of matter in suspensions containing such highly flexible fibres had never really been attempted before,” said postdoctoral researcher Antonio Perazzo. “Pursuing novel research has given us this unprecedented result of flow-induced gelation with flexible fibres.”
The next stage of the research will be to understand the mechanics of the thickening process in order to optimise it, as well as to add other substances such as antibiotics or nutrients for a number of biomedical purposes.
“We can envision these easily-injectable hydrogels being made to include different kinds of drugs beneficial to wound healing, for example,” said Stone. “There is considerable multifunctionality you can get out of a material with these properties.”
Proceedings of the National Academy of Sciences doi.org/cg79
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