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Chemistry In Pictures

Chemistry in Pictures: Expand

by Craig Bettenhausen
June 21, 2023


A tube made of wire and white fabric compressed, partially expanded, and expanded sit on a table.
Credit: Craig Bettenhausen/C&EN

This medical device serves as a scaffold for compromised structures in the human heart, and it is a cornucopia of interesting materials. The wavy wires are nitinol, an alloy of nickel and titanium that has excellent shape memory. It can bend, twist, and otherwise take abuse and it will still spring back into its manufactured shape inside the blood vessel the device will support. A number of gold rings that aren’t visible in this photo, but do show up well in ultrasound and x-ray images, help doctors place the tubes in just the right spot. And the white fabric is actually multiple layers of fluorinated ethylene propylene polymer and expanded polytetrafluoroethylene, the marquee inert material of its maker, W.L. Gore. Put it all together, and you have a stent-like device that comes compressed on a laparoscopic wire, which doctors insert into a patient’s artery through a small incision, often in the leg. The clinician then snakes the wire up to a structurally compromised blood vessel near the heart, gets it in a position, and pulls a rip-cord to let the tube pop into its expanded shape. Wire and rip-cord then sneak back out the way they came, leaving the synthetic support permanently installed to keep blood flowing smoothly.

Credit: Craig Bettenhausen/C&EN

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