Injectable "Microrobots" Can Wrap Around Your Bones — and Grow Their Own Bones, Too
Inspired by how fontanelle tissue turns to bone in newborn children, these novel robots could one day heal breaks from the inside.
An international team of researchers at the universities of Linköping in Sweden and Okayama in Japan have created a novel technology for "microrobots" inspired by the conversion of fontanelle tissue to bone in children — and which are capable of building their own artificial bones.
"We want to use this [growth process] for applications where materials need to have different properties at different points in time," explains Edwin Jager, associate professor and corresponding author of the work. "Firstly, the material is soft and flexible, and it is then locked into place when it hardens. This material could be used in, for example, complicated bone fractures. It could also be used in microrobots – these soft microrobots could be injected into the body through a thin syringe, and then they would unfold and develop their own rigid bones."
The system works by growing an electroactive polymer in alginate, then applying a low voltage to alter its volume - causing it to bend in a specified direction. Biomolecules known as plasma membrane nanofragments (PMNFs), taken from cells responsible for bone growth, are attached to the other side and allow the gel to harden — inspired by how the soft fontanelle tissues found in newborn children are gradually replaced by hard bone.
The team believes the microrobots could be used medically, potentially as a way of treating broken bones. In testing, they successfully had the material wrap itself around chicken bones and begin growing its artificial bone material — which grew together with the natural bone beneath.
"By controlling how the material turns, we can make the microrobot move in different ways, and also affect how the material unfurls in broken bones," Jager claims. "We can embed these movements into the material's structure, making complex programs for steering these robots unnecessary."
The concept could stretch further, too — including in the assistance of implanting or protecting electronic devices. "PMNF-based biohybrid materials could be used in new tools for tissue engineering, including robot-assisted surgical interventions, such as morphing bioadhesives, to adhere (electronic) components to bone, or to create a hard protective shell around such electronic components that integrates into the body," the team concludes in the paper.
The work has been published in the journal Advanced Materials under open-access terms.