Press a piece of tape against glass: it holds firmly, but run a warm finger over it, and the film lifts off on its own, leaving no marks. That's exactly how the new material behaves, made from liquid crystal elastomers — polymers whose molecules are arranged like a liquid crystal.
Usually, such polymers are stiff and glassy at room temperature, so they don't stick well. The authors added tiny amounts of a catalyst to the mix — a substance that alters the polymer network structure during UV exposure. Just a few parts per million of catalyst were needed, but it made the network sparser and more flexible. As a result, the material became soft under normal conditions: its stiffness dropped to 0.3 MPa, about the same as a soft rubber band, and its glass transition temperature fell to nearly zero degrees.
The secret to easy release lies in the liquid crystal order. In its normal state, the molecules are aligned, and the material is sticky. But when heated above the transition to the isotropic state (where order disappears), it suddenly loses tack and peels away from the surface. This switch is reversible: as it cools, the material becomes sticky again. This behavior resembles a thermal switch, except instead of breaking an electrical circuit, it breaks the adhesive contact.
A warm touch, and the tape peels off by itself, ready for another use.
The cobalt-based catalyst used in this work is so active that it's added at concentrations of just a few parts per million. That's like one drop of ink in a bathtub of water.
In Andy Weir's novel The Martian, the protagonist uses duct tape to repair his spacesuit — with such a switchable adhesive, he could peel off patches without leaving residue and reuse them.