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A mechanical crack-based sensor inspired by the mechanism spiders use to sense minute variations in stress offers ultrahigh sensitivity to pressure and vibration and can easily be mounted on human skin for the purposes of speech recognition and the monitoring of physiological signals.

Measuring cardiac contractility is challenging. Here, the authors encapsulated a crack-based sensor with polydimethylsiloxane, thereby endowing the sensor with the stability to measure cardiac contractility for up to 26 days as well as monitoring drug-induced cardiac toxicity in cell culture.

Two-dimensional structures introduced into perovskite solar cells improve performance yet their morphological and dimensional control remains challenging. Jang et al. devise a solid-phase approach to grow phase-pure two-dimensional perovskites over bulk perovskite, which affords greater device efficiency and stability.

A 3D-printing strategy involving jets of charged aerosol particles guided by electric-field lines allows direct deposition of various metal nanostructures, including helices, letters and vertical split-ring resonator structures.

The grain boundaries in thin-film perovskite solar cells are responsible for non-radiative carrier recombination, which is deleterious for the optoelectronic performance. Son et al. show how to passivate the grain boundaries by using excess CH₃NH₃I in the precursor solution, achieving efficiencies of 20.4%.

A discrepancy exists between the low diffusion coefficients and near-unity charge collection efficiencies achieved in practical halide perovskite solar cells. Here, the authors explain this through the discovery of strong heterogeneity in vertical charge diffusivities in a 3D perovskite film.

Improving the stability of perovskite solar cells remains crucial. Here, Ahn et al. show that trapped charges at grain boundaries induce the dissociation of the perovskite compound in the presence of moisture, and explain why degradation is irreversible under illumination and reversible in the dark.

Graphene’s exotic properties make it suitable for many different optoelectronic devices. Brar et al. show that graphene plasmonic resonators can be exploited to produce narrow spectral emission in the mid-infrared, whose frequency and intensity can be modulated by electrostatic gating.

Free-standing membranes are widely used as device templates, but their fabrication is limited to silicon-based materials nowadays. Cho et al. introduce a hierarchical mould-based dewetting approach to generate soft polymeric membranes with controllable multiple levels of nano-apertures over large areas.

Multiplex lithography is a technique that can be used to fabricate complex soft materials. Here, the authors develop a method to prepare multilevel multiscale structures and demonstrate its application on polymer electrolyte membrane fuel cells which display decreased membrane resistance and increased electrochemical active surface area.

Inspired by the rolling mechanism of the proboscis of a butterfly, a rollable electronics which can be rolled and unrolled on demand is developed. The rollable platform provides sufficient force which grips onto the entire target surface without destroying the target. Micro bio-objects are gripped by using the rollable platform and their tiny motions are successfully detected with the sensor on the platform. Furthermore, detecting pulse wave signals of the swine is successfully conducted by rolling up the rollable system around the blood vessel of swine, which result proves the feasibility of rollable platform as a biomedical device.

The capability of fabricating lightweight, small and flexible power sources is a key to cope with the increasing demand for smart and ubiquitous energy sources for current and future flexible electronics. We herein report a portable, lightweight and rollable polymer electrolyte membrane fuel cell. Because of its highly thin and flexible design, the device exhibited excellent durability against repetitive bending and easily deformed to any desired shape such as rolled-up or S-shape geometries. In addition, we introduced a portable flexible planar stack that demonstrates real practical applications of these devices.