2023-12-15 16:02:26
Using a unique 3D printing process, researchers at TU Delft have created hybrid connections from multiple materials that come remarkably close to the natural design of bone-tendon connections. The toughness value of the connection is 50% higher. The possible applications are countless. The team itself wants, among other things, to make connections with living cells in order to connect implants to surrounding soft tissue.
The results of the Delft researchers led by Professor Admir Zadpoor have been published in Nature Communication. The 3D printing process they developed has numerous potential applications, including in medical devices, soft robotics and flexible devices.
Inspiration from human body
Despite the large difference in hardness between bones and tendons, this connection normally never breaks in the human body. It is this bone-tendon connection that inspired the team of researchers from the Faculty of Mechanical Engineering, Maritime Technology and Applied Materials Sciences (3mE) to optimize the hard-soft transition of man-made materials. Because if there is a mismatch between the materials, tensions arise and the connection breaks down.
Gradual change
One of the things you see in nature is a gradual change in properties. “A hard material does not suddenly become a soft material,” says Professor of Biomaterials and Tissue Biomechanics, Amir Zadpoor. “It changes gradually and that levels off the tension concentration.” With that in mind, the researchers used different configurations and a multi-material 3D printing technique to increase the contact surface between hard and soft materials, mimicking the design found in nature. Another consideration is that the force a soft material can withstand before failure is lower than that of a hard material. “It is only relevant to make the transition as strong as the soft material, because if it is stronger, the soft material will fail,” says Mauricio Cruz Saldivar, the first author of the manuscript.
Toughness value 50% higher
The researchers managed to increase the toughness value of the compounds by 50% compared to the control group. Approaching the limits of what is theoretically possible is one of the most important contributions of this research, according to the team. But the research also led to design guidelines for improving the mechanical performance of soft-hard connections, and these principles are universally applicable.
Countless applications conceivable
Thanks to the development from Delft, more products can be 3D printed at once, which now often consist of glued or mechanically connected components. This means that it is now possible to combine very different materials. Potential applications include medical devices, soft robotics and flexible devices. But the team also wants to investigate how they can make connections with living cells, for example to connect implants to the surrounding soft tissue. “Ultimately, we want to regenerate bone and the connection between bone and muscle,” says Assistant Professor Mohammad J. Mirzaali. “That would mean that we would have to integrate living cells into this connection, which increases the complexity of the construction.”
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