Published On Jan 18, 2017
Devices That Bloom
A new shape-shifting material would let surgical implants grow in place.
Some medical devices need to change shape once they’ve been implanted into the body. Stents, for instance, typically enter through a small incision, then expand to support a vein or another structure. But these adjustments all require an external trigger: a mechanical nudge, a chemical variation or even a shift in light or temperature.
What if a device changed form all on its own? A team of researchers at the University of North Carolina led by Sergei Sheiko has developed a material that can do just that. To show its range, the team created a synthetic flower, which they programmed to bloom over two hours, with each petal unfolding at a pre-determined time—producing one of the more picturesque studies to be published in Nature Communications.
The material is a hydrogel, the same material used to make contact lenses. Within it, two polymer networks overlap in different configurations to control the timing of the growth. One network, formed from stronger chemical bonds, provides rigidity to the shape and stores elastic energy—a tension that can be translated into movement later. The other network, formed from weaker bonds that break and re-form during the transformation, control the speed at which the energy is released. Sheiko and his team can distribute these networks in different concentrations to make the structure unfold as quickly or slowly as they need.
The material has not yet been tested in the human body, but applications might include new designs for implanted devices that need to be inserted through small incisions and then occupy a larger space inside the body. Drug-release systems offer another frontier; a device might be programmed to change shape and slowly release a medication, or a series of medications, over weeks or months.