It has a soft polymer mesh body wrapped in nickel and titanium wire "which is essentialy compliant, exhibits large strains and enables the robot to traverse small openings and reconstitute shape, and survices from large impact on falling," say the researchers.
This method of soft-body construction, as opposed to using gears and pumps, makes the worm's operation very quiet which is a key part of its purpose because the project was funded by Darpa which wants to use the worm for military reconnaissance.
The worm can wriggle along at 5mm a second. The wire partitions the soft body into five segments which can be contracted by putting a charge through the wire on successive segments causing that segment to contract and push itself forward.
The worm, called by the researchers 'Meshworm', can survice being trodden on or hit with a hammer.