Implantable optoelectronic devices, which are based on microscale light-emitting diodes (micro-LEDs) and are capable of wireless power harvesting, offer precise control over their optical output for use in complex optogenetic experiments. The cover shows a photograph of one of these flexible devices balanced on a finger.

See Gutruf et al. and News & Views by Sohal

An electronic-skin compass, which is fabricated on 6-μm-thick polymeric foils and accommodates magnetic field sensors based on the anisotropic magnetoresistance effect, allows a person to orient with respect to Earth’s magnetic field and to manipulate objects in virtual reality. The cover shows a scanning electron microscopy image of the compass under a bending radius of 200 μm.

See Makarov et al. and News & Views by Heidari

High-performance microthermoelectric coolers, which are composed of pairs of thermoelectric ‘legs’ and convert electricity into cooling, can be fabricated using methods compatible with the modern semiconductor industry. The cover shows a scanning electron microscopy image of the integrated microthermoelectric device, which has a packing density of around 5,000 leg pairs per cm2.

See Li et al. and News & Views by Vaughan

Developing laboratory equipment that is affordable and accessible to many could encourage a greater diversity of scientific thinking – an endeavour that the field of soft electronics can help lead. The cover shows a photograph of a radial stretching system that is made from laser-cut acrylic parts and 3D-printed components, and is powered by an Arduino single-board computer. It is being used to test a stretchable micro-LED array with serpentine interconnects.

See Comment by Drack et al.

By stacking, and electrically connecting, layers of stretchable circuits, three-dimensional integrated devices can be built that are capable of wirelessly monitoring a person’s vital signs and creating human–machine interfaces. The cover shows an optical microscopy image of a four-layer stretchable device that is equipped with Bluetooth data communication capabilities and can simultaneously sense electrophysiological signals, strain, temperature, acceleration, and orientation.

See Huang et al. and News & Views by Kim et al.

The sub-terahertz rotational transitions of polar gas molecules can be used as a frequency base to create chip-scale molecular clocks. The cover shows a photograph of the CMOS transmitter chip that is used, together with a receiver chip, to create the low-cost, low-power miniaturized clocks.

See Wang et al. and News & Views by Kitching

Electrons that tunnel through a thin ferromagnetic chromium tribromide barrier, sandwiched between graphene electrodes, are forced to emit magnons in order to fulfil momentum conservation conditions, which suggests that such tunnel barriers could be used for spin injection. The cover shows an optical microscopy image of the trilayer heterostructure, which is encapsulated by hexagonal boron nitride and placed on a silicon/silica substrate.

See Ghazaryan et al. and News & Views by Valenzuela et al.

Individual magnetic skyrmions — topologically protected spin textures — can be created and destroyed at room temperature in ferrimagnetic films using current pulses, a process that can be directly observed with time-resolved X-ray microscopy. The schematic illustration on the cover highlights the whirl-like magnetic configuration of the ferrimagnetic skyrmions.

See Woo et al. and News & Views by Everschor-Sitte et al.

Specially designed computing boards, which combine eight field-programmable gate arrays, can generate holograms with a video frame rate. The cover shows a 100-million-pixel hologram of a planetary exploration satellite created using the holography computing board.

See Sugie et al. and News & Views by Chu

The analogue tuning properties of memristors can be used to create physically unclonable functions, a type of hardware security primitive that draws its cryptographic keys from physical variations created during device fabrication. The schematic illustration on the cover highlights the experimental implementation of these ‘digital fingerprints’, which rely on vertically integrated metal-oxide memristive crossbar circuits.

See Nili et al.

Efficient and magnet-free isolators can be built by coupling two nonlinear resonators through a suitable delay line. The schematic illustration on the cover highlights the combination of a Fano and a Lorentzian nonlinear resonator circuit, where the tailored dispersion of the two resonators enables full transmission when excited from one side, but zero transmission when excited from the opposite side.

See Sounas et al. and News & Views by Krishnaswamy et al.

Large memristor arrays have been shown to be capable of analogue vector-matrix multiplication, illustrating their potential for use in Internet of Things (IoT) and edge computing applications. The cover shows a photograph of an integrated chip containing memristor crossbar arrays of various sizes.

See Li et al. and News & Views by Wu et al.