Three-dimensional (3D) structures capable of reversible transformations in their geometrical layouts have important applications across a broad range of areas. Most morphable 3D systems rely on concepts inspired by origami/kirigami or techniques of 3D printing with responsive materials. The development of schemes that can simultaneously apply across a wide range of size scales and with classes of advanced materials found in state-of-the-art microsystem technologies remains challenging. Here, we introduce a set of concepts for morphable 3D mesostructures in diverse materials and fully formed planar devices spanning length scales from micrometers to millimeters. The approaches rely on elastomer platforms deformed in different time sequences to elastically alter the 3D geometries of supported mesostructures via non-linear mechanical buckling. Over 20 examples have been experimentally and theoretically investigated, including mesostructures that can be reshaped between different geometries as well as those that can morph into three or more distinct states. An adaptive radio frequency circuit and a concealable electromagnetic device provide examples of functionally reconfigurable microelectronic devices.

Recent progress in stretchable forms of inorganic electronic systems has established a route to new classes of devices, with particularly unique capabilities in functional biointerfaces, because of their mechanical and geometrical compatibility with human tissues and organs. A reliable approach to physically and chemically protect the electronic components and interconnects is indispensable for practical applications. Although recent reports describe various options in soft, solid encapsulation, the development of approaches that do not significantly reduce the stretchability remains an area of continued focus. Herein, a generic, soft encapsulation strategy is reported, which is applicable to a wide range of stretchable interconnect designs, including those based on twodimensional (2D) serpentine configurations, 2D fractal-inspired patterns, and 3D helical configurations. This strategy forms the encapsulation while the system is in a prestrained state, in contrast to the traditional approach that involves the strain-free configuration. A systematic comparison reveals that substantial enhancements (e.g., ≈6.0 times for 2D serpentine, ≈4.0 times for 2D fractal, and ≈2.6 times for 3D helical) in the stretchability can be achieved through use of the proposed strategy. Demonstrated applications in highly stretchable lightemitting diodes systems that can be mounted onto complex curvilinear surfaces illustrate the general capabilities in functional device systems.

Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.

The miniaturization of electronics has been an important topic of study for several decades. The established roadmaps following Moore's Law have encountered bottlenecks in recent years, as planar processing techniques are already close to their physical limits. To bypass some of the intrinsic challenges of planar technologies, more and more efforts have been devoted to the development of 3D electronics, through either direct 3D fabrication or indirect 3D assembly. Recent research efforts into direct 3D fabrication have focused on the development of 3D transistor technologies and 3D heterogeneous integration schemes, but these technologies are typically constrained by the accessible range of sophisticated 3D geometries and the complexity of the fabrication processes. As an alternative route, 3D assembly methods make full use of mature planar technologies to form predefined 2D precursor structures in the desired materials and sizes, which are then transformed into targeted 3D mesostructures by mechanical deformation. The latest progress in the area of micro/nanoscale 3D assembly, covering the various classes of methods through rolling, folding, curving, and buckling assembly, is discussed, focusing on the design concepts, principles, and applications of different methods, followed by an outlook on the remaining challenges and open opportunities.

Elastic stretchability and function density represent two key figures of merits for stretchable inorganic electronics. Various design strategies have been reported to provide both high levels of stretchability and function density, but the function densities are mostly below 80%. While the stacked device layout can overcome this limitation, the soft elastomers used in previous studies could highly restrict the deformation of stretchable interconnects. Here, we introduce stacked multilayer network materials as a general platform to incorporate individual components and stretchable interconnects, without posing any essential constraint to their deformations. Quantitative analyses show a substantial enhancement (e.g., by ~7.5 times) of elastic stretchability of serpentine interconnects as compared to that based on stacked soft elastomers. The proposed strategy allows demonstration of a miniaturized electronic system (11 mm by 10 mm), with a moderate elastic stretchability (~20%) and an unprecedented areal coverage (~110%), which can serve as compass display, somatosensory mouse, and physiological-signal monitor.

Dielectric ceramics are crucial for high-temperature, pulse-power energy storage applications. However, the mutual restriction between the polarization and breakdown strength has been a significant challenge. Here, multiphase engineering controlled by the two-step sintering heating rate is adopted to simultaneously obtain a high polarization and breakdown strength in 0.8(0.95Bi 0.5 Na 0.5 TiO 3 − 0.05SrZrO 3 )−0.2NaNbO 3 (BNTSZNN) ceramic systems. The coexistence of tetragonal (T) and rhombohedral (R) phases benefits the temperature stability of BNTSZNN ceramics. Increasing the heating rate during sintering reduces the diffusion of SrZrO 3 and NaNbO 3 into Bi 0.5 Na 0.5 TiO 3 , which results in a high proportion of the R phase and a finer grain size. The overall polarization is enhanced by increasing the proportion of the high-polarization R phase, which is demonstrated using a first-principles method. Meanwhile, the finer grain size enhances the breakdown strength. Following this design philosophy, an ultrahigh W dis of 5.55 J/cm 3 and η above 85% is achieved in BNTSZNN ceramics as prepared with a fast heating rate of 60 °C/min given a simultaneously high polarization of 43 μC/cm 2 and high breakdown strength of 350 kV/cm. Variations in the discharge energy density from room temperature to 160 °C are less than 10%. Additionally, such BNTSZNN ceramics exhibit an ultrafast discharge speed with τ 0.9 at approximately 60 ns, which shows great potential in pulse-power system applications.

Abstract3D structures that incorporate high‐performance electronic materials and allow for remote, on‐demand 3D shape reconfiguration are of interest for applications that range from ingestible medical devices and microrobotics to tunable optoelectronics. Here, materials and design approaches are introduced for assembly of such systems via controlled mechanical buckling of 2D precursors built on shape‐memory polymer (SMP) substrates. The temporary shape fixing and recovery of SMPs, governed by thermomechanical loading, provide deterministic control over the assembly and reconfiguration processes, including a range of mechanical manipulations facilitated by the elastic and highly stretchable properties of the materials. Experimental demonstrations include 3D mesostructures of various geometries and length scales, as well as 3D aquatic platforms that can change trajectories and release small objects on demand. The results create many opportunities for advanced, programmable 3D microsystem technologies.

In article number 1901895, Yihui Zhang and Xu Cheng discuss the latest progress and new perspectives of micro‐/nanoscale 3D assembly, highlighting the various methods, through rolling, folding, curving, and buckling assembly. Owing to their broad‐ranging applicability to different material systems, the resulting 3D micro‐/nanostructures have compelling applications in widespread areas, from electronics/optoelectronics, and microelectromechanical systems (MEMS), to medical devices and cell scaffolds.