If you had to grasp a tiny delicate object such as a blood vessel, doing so with traditional tweezers would be a very painstaking process – just a little too much pressure, and the object could be crushed. Instead, scientists from Iowa State University have developed miniature coiling tentacles for doing the job. They're even capable of holding an ant without harming it.
The tentacles are actually microtubes measuring just 8 mm long by about a quarter of a millimeter across, that are composed of polydimethylsiloxane (PDMS) elastomer.
To make the tubes, the researchers start by dipping a rod-shaped cylindrical template in a bath of liquid PDMS. After being pulled out of the bath, the PDMS-coated template is left to cure in a horizontal orientation. As it does so, gravity pulls much of the gelling elastomer down to the underside of the template, making the coating thinner on top and thicker on the bottom.
Once the PDMS has set to a soft rubbery consistency, it's peeled off of the template, resulting in a hollow microtube. One end of that tube is then plugged, while air is pumped in through the other end. Because the tube's wall is thicker on one side than the other, the tube as a whole coils towards the thinner side as it stiffens with the higher air pressure.
In order to accentuate the coil, a lump of PDMS is added to the base of the microtube on the outside of its thin side – this adds structural support to that area, stopping it from curling and concentrating the coiling action in the "downstream" section of the tube.
A paper on the research was recently published in the journal Scientific Reports.
Source: Iowa State University
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