From artificial organs to advanced batteries: A breakthrough 3D-printable polymer

A new type of 3D-printable material that gets along with the body’s immune system, pioneered by a University of Virginia research team, could lead to safer medical technology for organ transplants and drug delivery systems. It could also improve battery technologies.

The breakthrough is the subject of a new article in the journal Advanced Materials, based on work done by the University of Virginia’s Soft Biomatter Laboratory, led by Liheng Cai, an associate professor of materials science and engineering and chemical engineering. 

The paper’s first author is Baiqiang Huang, a Ph.D. student in the School of Engineering and Applied Science.

Their research shows a way to change the properties of polyethylene glycol to make stretchable networks. PEG, as it’s known, is a material already used in many biomedical technologies such as tissue engineering, but the way PEG networks are currently produced — created in water by crosslinking linear PEG polymers, with the water removed afterward — leaves a brittle, crystallized structure that can’t stretch without losing its integrity. 

The breakthrough in elasticity is an important feature, because stretchiness would allow PEG networks’ use in larger structures, or in structures that require some flexibility and movement, such as the scaffolding needed someday for synthetic human organs. 

Stretch Lies in Foldable Design

To create this stretchiness, the team built upon existing work from Cai’s lab, which had already developed a way to create very strong synthetic polymers. The approach took a page from the methods used to create stretchy, strong rubber: store length in internal structures at the molecular level. 

These internal structures, called a “foldable bottlebrush” design, make for a material that can be both very strong and very stretchy. The polymeric molecules have many flexible side chains radiating out from a central backbone that can collapse like an accordion — storing extra length that can be unfolded.

“Our group discovered this polymer and used this architecture to show any materials made this way are very stretchable.” Cai said.

To create the new material described in Advanced Materials, Huang applied the foldable bottlebrush polymer concept to PEG. He exposed the precursor mixture to ultraviolet light for a few seconds, which initiates polymerization to form a bottlebrush-architecture network. This resulted in 3D-printable, highly stretchable PEG-based hydrogels and solvent-free elastomers. 

“We can change the shape of the UV lights to create so many complicated structures,” Huang said, including structures that are either soft or stiff but remain stretchy by design. This type of versatility in design could one day allow for the creation of new techniques for creating artificial organs or delivery medicines. 

The paper also shows that the stretchy 3D-printable PEG materials are biologically friendly. The researchers cultured cells alongside the materials, to make sure they can live side-by-side, and they were compatible, Huang said. This is good news for its potential use for materials that would go inside the body, such as scaffolding for an organ. 

Future Applications

In a future application, it might also be possible to combine PEG with other materials to create 3D-printable materials with different chemical compositions, opening the door to many possible uses. 

For example, compared to existing materials for solid-state polymer electrolytes, the new materials show greater electrical conductivity and much higher stretchability at room temperature. 

“This property highlights the new material as a promising high-performance solid-state electrolyte for advanced battery technologies,” Cai said. “Our team continues to explore potential extensions of the research in solid-state battery technologies.” 

The paper’s other authors include UVA Engineering colleagues Myoeum Kim, Pu Zhang, Emmanuel Oduro and Daniel A. Rau. The work was funded by the National Science Foundation, National Institutes of Health, UVA LaunchPad for Diabetes and Virginia Innovation Partnership Corporation’s Commonwealth Commercialization fund. 

The paper, “Additive Manufacturing of Molecular Architecture Encoded Stretchable Polyethylene Glycol Hydrogels and Elastomers,” was published in Advanced Materials on Oct. 29.