Highly bendable yet unstretchable ultrathin sheets can wrap a liquid droplet to form an optimal non-spherical shape that minimizes the unwrapped interfacial area, regardless of interfacial energies and the sheet's mechanical properties.

Letter p1206

IMAGE: JOSEPH PAULSEN

COVER DESIGN: DAVID SHAND

Experiments and coarse-grained simulations show, in an active system based on microtubules, a system-spanning phase of motile defects with orientational order that persists over hours despite a defect lifetime of seconds.

Letter p1110; News & Views p1084

IMAGE: STEPHEN J. DECAMP

COVER DESIGN: DAVID SHAND

The use of a chromium oxide interlayer separating the perovskite film from the metal contacts improves the stability of perovskite solar cells in air. Deposited on thin plastic foils, these ultralight devices power model airplanes and dirigibles.

Article p1032; News & Views p964

IMAGE: MARTIN KALTENBRUNNER

COVER DESIGN: DAVID SHAND

Intraband optical spectroscopy — which uses an ultrashort mid-infrared probe pulse and a visible pump pulse — can image the bright and dark exciton dynamics simultaneously in a transition metal dichalcogenide monolayer.

Letter p889; News & Views p860

IMAGE: BRAD BAXLEY

COVER DESIGN: DAVID SHAND

Networks of notches in nanocomposite sheets prevent unpredictable local failure and increase the ultimate strain of the sheets from 4% to 370% without affecting their electrical conductance.

Letter p785

IMAGE: MATTHEW SHLIAN

COVER DESIGN: DAVID SHAND

Manipulating strain states to modulate ionic conduction in micro energy devices has proved difficult. Effective net strain is now used to control oxygen ionic transport kinetics in ceria-based electrolyte membranes.

Article p721

IMAGE: YANUO SHI, KAMILA KAWECKA AND ALEXANDER HANSEN BORK

COVER DESIGN: DAVID SHAND

The thermal conductivity of diamagnetic InSb decreases as a magnetic field is increased at low temperatures, and is attributed to local dynamic diamagnetism, providing evidence of the magnetic response of phonons.

Article p601

IMAGE: R. L. RIPLEY, WITH CONTRIBUTIONS FROM O. RESTREPO, N. ANTOLIN AND W. WINDL

COVER DESIGN: DAVID SHAND

Efficient in vivo cytosolic delivery of nucleic acids through cell-membrane puncturing by an array of biodegradable silicon nanoneedles induces sustained local neovascularization in muscle.

Article p532; News & Views p470

IMAGE: CIRO CHIAPPINI AND MATT LANDRY

COVER DESIGN: DAVID SHAND

Molecular beam epitaxy now enables the growth of nanowire heterostructures composed of a semiconducting core and a metallic epitaxial shell. This improved synthesis leads to the creation of a hard superconducting gap with no subgap states.

Article p400

IMAGE: CENTER FOR QUANTUM DEVICES, NIELS BOHR INSTITUTE

COVER DESIGN: DAVID SHAND

The lifting of valley degeneracy in the monolayer transition metal dichalcogenide WS2 is now demonstrated by the optical Stark effect, showing that each valley can be selectively tuned by up to 18 meV.

Letter p290

IMAGE: ELLA MARUSHCHENKO AND ALEX TOKAREV

COVER DESIGN: DAVID SHAND

The direction of the current photogenerated in organic–inorganic perovskite films can be switched by poling the material with low electric fields that induce a reversible ion drift. Hybrid perovskites may thus find application as memristor devices.

Letter p193; News & Views p140

IMAGE: ZHENGGUO XIAO

COVER DESIGN: DAVID SHAND

Single-particle-resolution video microscopy of films of colloidal particles shows that solid–solid transitions between square and triangular lattices occur through a two-step nucleation mechanism that involves liquid nuclei.

Article p101; News & Views p15

IMAGE: YI PENG

COVER DESIGN: DAVID SHAND