Researchers have developed a way to 3D-print tough, fiber-reinforced hydrogels that mimic the strength and suppleness of human cartilage.

Thanks to their composition (mostly water), hydrogels hold much promise for use in medical bionic applications, their softness being more readily acceptable to the body than hard materials. However, despite naturally occurring hydrogels (like cartilage) being mechanically robust, conventional synthetic hydrogels tend to be too structurally weak for many medical applications.

Shannon Bakarich (pictured above), a PhD candidate at the ARC Centre of Excellence for Electromaterials Science based at UOW, has come up with a solution in the form of 3D printed, fiber-reinforced hydrogels.

To create his toughened hydrogel, Shannon simultaneously prints with two inks on a 3D printer customized with a UV curing system. One ink cures into a soft and wet hydrogel and the other, to a hard and stiff plastic which forms the reinforcing ‘fibers’ within the structure.

“Using computer aided design software, I can make a digital model of the fibers and hydrogel matrix, tuning the mechanical properties by carefully controlling the distribution of the fibers within our structures,” Shannon said.

“The printed fibers give strength to the hydrogel in the same way fiber glass gives strength to a surfboard.”

The key to Shannon’s success was carefully balancing the properties of the two inks so that they could be printed side by side in the same print job.

While scientists have previously used 3D printing to create fiber-reinforced hydrogels, a two-step process has been used to combine the two variations in materials. This new method uses a one-step printing process, giving greater control over the 3D distribution of the fibers in a faster and simpler process.

To demonstrate the potential of his 3D printed, fiber-toughened hydrogels, Shannon produced a knee cartilage prototype, mimicking the hydrogel and fiber structure of a real cartilage. Despite being an early prototype, the cartilage model demonstrates the potential of the process for use in developing multi-component hydrogel structures for soft robotics and medical bionics.