Electronic skin devices capable of monitoring physiological signals and displaying feedback information through closed-loop communication between the user and electronics are being considered for next-generation wearables and the 'Internet of Things'. Such devices need to be ultrathin to achieve seamless and conformal contact with the human body, to accommodate strains from repeated movement and to be comfortable to wear. Recently, self-healing chemistry has driven important advances in deformable and reconfigurable electronics, particularly with self-healable electrodes as the key enabler. Unlike polymer substrates with self-healable dynamic nature, the disrupted conducting network is unable to recover its stretchability after damage. Here, we report the observation of self-reconstruction of conducting nanostructures when in contact with a dynamically crosslinked polymer network. This, combined with the self-bonding property of self-healing polymer, allowed subsequent heterogeneous multi-component device integration of interconnects, sensors and light-emitting devices into a single multi-functional system. This first autonomous self-healable and stretchable multi-component electronic skin paves the way for future robust electronics.

Sensing the force digitally Our skin provides us with a flexible waterproof barrier, but it also contains a sensor array that feels the world around us. This array provides feedback and helps us to avoid a hot object or increase the strength of our grip on an object that may be slipping away. Tee et al. describe an approach to simulate the mechanoreceptors of human skin, using pressure-sensitive foils and printed ring oscillators (see the Perspective by Anikeeva and Koppes). The sensor successfully converted pressure into a digital response in a pressure range comparable to that found in a human grip. Science , this issue p. 313 ; see also p. 274

Increasing performance demands and shorter use lifetimes of consumer electronics have resulted in the rapid growth of electronic waste. Currently, consumer electronics are typically made with nondecomposable, nonbiocompatible, and sometimes even toxic materials, leading to serious ecological challenges worldwide. Here, we report an example of totally disintegrable and biocompatible semiconducting polymers for thin-film transistors. The polymer consists of reversible imine bonds and building blocks that can be easily decomposed under mild acidic conditions. In addition, an ultrathin (800-nm) biodegradable cellulose substrate with high chemical and thermal stability is developed. Coupled with iron electrodes, we have successfully fabricated fully disintegrable and biocompatible polymer transistors. Furthermore, disintegrable and biocompatible pseudo-complementary metal-oxide-semiconductor (CMOS) flexible circuits are demonstrated. These flexible circuits are ultrathin (<1 μm) and ultralightweight (∼2 g/m) with low operating voltage (4 V), yielding potential applications of these disintegrable semiconducting polymers in low-cost, biocompatible, and ultralightweight transient electronics.

For molecules to be used as components in molecular machines, methods that couple individual molecules to external energy sources and that selectively excite motion in a given direction are required. Significant progress has been made in the construction of molecular motors powered by light and by chemical reactions, but electrically driven motors have not yet been built, despite several theoretical proposals for such motors. Here we report that a butyl methyl sulphide molecule adsorbed on a copper surface can be operated as a single-molecule electric motor. Electrons from a scanning tunnelling microscope are used to drive the directional motion of the molecule in a two-terminal setup. Moreover, the temperature and electron flux can be adjusted to allow each rotational event to be monitored at the molecular scale in real time. The direction and rate of the rotation are related to the chiralities of both the molecule and the tip of the microscope (which serves as the electrode), illustrating the importance of the symmetry of the metal contacts in atomic-scale electrical devices.

Surface topography profoundly influences cell adhesion, differentiation, and stem cell fate control. Numerous studies using a variety of materials demonstrate that nanoscale topographies change the intracellular organization of actin cytoskeleton and therefore a broad range of cellular dynamics in live cells. However, the underlying molecular mechanism is not well understood, leaving why actin cytoskeleton responds to topographical features unexplained and therefore preventing researchers from predicting optimal topographic features for desired cell behavior. Here we demonstrate that topography-induced membrane curvature plays a crucial role in modulating intracellular actin organization. By inducing precisely controlled membrane curvatures using engineered vertical nanostructures as topographies, we find that actin fibers form at the sites of nanostructures in a curvature-dependent manner with an upper limit for the diameter of curvature at ∼400 nm. Nanotopography-induced actin fibers are branched actin nucleated by the Arp2/3 complex and are mediated by a curvature-sensing protein FBP17. Our study reveals that the formation of nanotopography-induced actin fibers drastically reduces the amount of stress fibers and mature focal adhesions to result in the reorganization of actin cytoskeleton in the entire cell. These findings establish the membrane curvature as a key linkage between surface topography and topography-induced cell signaling and behavior.

The introduction of microstructure to the metal-free graphitic carbon nitride (g-CN) photocatalyst holds promise in enhancing its catalytic performance. However, producing such microstructured g-CN remains technically challenging due to a complicated synthetic process and high cost. In this study, we develop a facile and in-air chemical vapor deposition (CVD) method that produces onion-ring-like g-CN microstructures in a simple, reliable, and economical manner. This method involves the use of randomly packed 350 nm SiO microspheres as a hard template and melamine as a CVD precursor for the deposition of a thin layer of g-CN in the narrow space between the SiO microspheres. After dissolution of the microsphere template, the resultant g-CN exhibits uniquely uniform onion-ring-like microstructures. Unlike previously reported g-CN powder morphologies that show various degrees of agglomeration and irregularity, the onion-ring-like g-CN is highly dispersed and uniform. The calculated band gap for onion-ring-like g-CN is 2.58 eV, which is significantly narrower than that of bulk g-CN at 2.70 eV. Experimental characterization and testing suggest that, in comparison with bulk g-CN, onion-ring-like g-CN facilitates charge separation, extends the lifetime of photoinduced carriers, exhibits 5-fold higher photocatalytic hydrogen evolution, and shows great potential for photocatalytic applications.

Membrane curvature participates in a wide range of cellular processes, and acts as a hotspot for protein interactions and intracellular signalling. Curvature also occurs at the interface between cells and nanotopography of biomaterials and biomedical devices, which could influence the performance of tissue engineering scaffolds and implantable devices. Precisely manipulating membrane curvature is thus of great interest in probing intracellular activities involved with curved membranes. Here we present a detailed protocol to design, fabricate, and characterize nanoscale structures for manipulating membrane curvature and probing curvature-induced phenomena in live cells. This protocol first describes a detailed procedure for the design and fabrication of nanoscale structures using electron-beam lithography. Then, the protocol describes how to use these nanostructures to manipulate local membrane curvature and probe intracellular protein responses. Finally, the protocol describes a procedure to characterize the nanostructure-cell membrane interface using focused ion beam and scanning electron microscopy.

Multielectrode arrays (MEAs) are essential tools in neural and cardiac research as they provide a means for noninvasive, multiplexed recording of extracellular field potentials with high temporal resolution. To date, the mechanical properties of the electrode material, e.g., its Young’s modulus, have not been taken into consideration in most MEA designs leaving hard materials as the default choice due to their established fabrication processes. However, the cell–electrode interface is known to significantly affect some aspects of the cell’s behavior. In this paper, we describe the fabrication of a soft 3D micropillar electrode array. Using this array, we proceed to successfully record action potentials from monolayer cell cultures. Specifically, our conductive hydrogel micropillar electrode showed improved signal amplitude and signal-to-noise ratio, compared with conventional hard iridium oxide micropillar electrodes of the same diameter. Taken together, our fabricated soft micropillar electrode array will provide a tissue-like Young’s modulus and thus a relevant mechanical microenvironment to fundamental cardiac and neural studies.