Tokyo University of Agriculture and Technology (TUAT) researchers have devised innovative methods for creating hydrogels—precisely fabricated, pliable, and stretchable materials.
The research builds on the new topic of "Kirigami hydrogels," which involves cutting patterns into thin film that then swells to create complex hydrogel structures. The findings are released in the Science and Technology of Advanced Materials journal.
Hydrogels have water-attracting molecules that make their structures swell when water enters the network. Researchers Itsuo Hanasaki and Daisuke Nakagawa experimented with an initially dry film made of cellulose nanofibers, a natural substance that makes up a large portion of the structure of plant cell walls.
They used laser processing to cut structures into the film before adding water to make it swell. The auxetic property refers to the specific method in which the Kirigami pattern's design causes the width to grow when stretched longitudinally. When the initial thin coating becomes sufficiently thick, this auxetic feature manifests itself as long as it remains moist.
According to Hanasaki, Kirigami was initially meant for thin sheet structures. However, when the sheet is thick enough, their two-dimensional auxetic process becomes apparent, and when the hydrogel structure is applied, its three-dimensionality is revealed by swelling. It is more convenient to store it dry before using it as opposed to maintaining the hydrogel's same water content.
Adaptive hydrogels can be used in soft robotic components to provide flexibility when the robots interact with objects. They may also be included in sensor and soft switch components.
Hydrogels have various medical applications. They can adapt to movement and growth, deliver drugs, aid in tissue engineering, and be used for wound dressings. The TUAT team's advancement in kirigami hydrogels greatly expands the possibilities for hydrogel uses in the future.
