Nature Commun. 6, 7590 (2015)

Research on metamaterials has recently shifted towards the dynamic tunability of their properties in an effort to overcome limitations in, for example, bandwidth, fabrication and tolerance. Now, Wiktor Lewandowski, Martin Fruhnert and colleagues have demonstrated a metamaterial whose properties can be actively tuned with temperature. The silver nanoparticles coated with a thermally switchable ligand showed a different arrangement at high and low temperatures. At 120 °C, the particles had a separation distance of 7.2 nm, whereas when the temperature was lowered, they moved closer (6 nm) and formed distinct layers; the plasmon band blueshifted by 20 nm and the metamaterials exhibited epsilon-near-zero properties at both extremes. The process is fully reversible, albeit slow (about 60 min is required to lower the temperature). Although the tunability range and reconfiguration timescales need to be improved, these findings underline the potential of self-assembly techniques based on liquid-crystalline surface ligands for reconfigurable metamaterials.