Additive manufacturing, i.e., 3D printing, is being increasingly utilized to fabricate a variety of complex-shaped electronics and energy devices (e.g., batteries, supercapacitors, and solar cells) due to its excellent process flexibility, good geometry controllability, as well as cost and material waste reduction. In this review, the recent advances in 3D printing of emerging batteries are emphasized and discussed. The recent progress in fabricating 3D-printed batteries through the major 3D-printing methods, including lithographybased 3D printing, template-assisted electrodeposition-based 3D printing, inkjet printing, direct ink writing, fused deposition modeling, and aerosol jet printing, are first summarized. Then, the significant achievements made in the development and printing of battery electrodes and electrolytes are highlighted. Finally, major challenges are discussed and potential research frontiers in developing 3D-printed batteries are proposed. It is expected that with the continuous development of printing techniques and materials, 3D-printed batteries with long-term durability, favorable safety as well as high energy and power density will eventually be widely used in many fields.

Silk is a natural fiber renowned for its outstanding mechanical properties that have enabled the manufacturing of ultralight and ultrastrong textiles. Recent advances in silk processing and manufacturing have underpinned a re-interpretation of silk from textiles to technological materials. Here, it is argued that silk materials-optimized by selective pressure to work in the environment at the biotic-abiotic interface-can be harnessed by human micro- and nanomanufacturing technology to impart new functionalities and opportunities. A critical overview of recent progress in silk technology is presented with emphasis on high-tech applications enabled by recent innovations in multilevel modifications, multiscale manufacturing, and multimodal characterization of silk materials. These advances have enabled successful demonstrations of silk materials across several disciplines, including tissue engineering, drug delivery, implantable medical devices, and biodissolvable/degradable devices.

a compelling need to utilize advanced technologies in the agriculture sector to increase agricultural productivity and reduce food losses to guarantee food security. [2] In this regard, "smart agriculture" or "precision agriculture" has been attracting increasing attention due to its capability for using less to grow more compared to traditional agricultural practices. In addition, it improves the quality of the work environment and social aspects of farming, ranching, and other relevant professions. [4] Smart agriculture comprises a set of technologies that combines sensors, information systems, enhanced machinery, and informed management to optimize production by accounting for variabilities and uncertainties within sustainable agricultural systems. [3][4][5] Among the set of technologies, advanced sensing systems that monitor soil health and conditions and crop developments are of paramount importance because they collect and evaluate critical data for decision making and management, especially when crop growth conditions vary considerably over space and time. Spatial variation may result from soil properties, diseases, weeds, pests, and previous land management. In particular, some soil properties (e.g., moisture, pH, nutrients) and plant diseases may form long-term spatial patterns. Temporal variability arises from weather patterns and management practices. In summary, the soil properties relevant to crop growth include a range of soil conditions including soil gas, moisture, temperature, nutrients, pH, and pollutants in the soil (Figure 1). [6,7] Monitoring the soil conditions will provide key information not only to improve resource utilization to maximize farming outputs and minimize environmental side effects but also to build site-specific databases of relationships between soil conditions and plant growth for intelligent and sustainable agriculture systems. Traditionally, soil properties are measured by soil sampling and offsite laboratory analysis or by on-site measurement to provide an extensive knowledge of soil information. [8] Seasonally varying crop growth conditions, such as water stress, lack of nutrients, diseases, weeds, and insects, are evaluated by visual inspection and laboratory analysis of plant tissues. The relatively periodically coarse sampling/measurement rate of these conventional strategies may not be sufficient to reveal variation at the appropriate spatial and temporal resolution. Novel technologies for collecting soil information with sufficient spatiotemporal resolutions are in demand to build efficient smart or precision agriculture systems. With the Soil sensors and plant wearables play a critical role in smart and precision agriculture via monitoring real-time physical and chemical signals in the soil, such as temperature, moisture, pH, and pollutants and providing key information to optimize crop growth circumstances, fight against biotic and abiotic stresses, and enhance crop yields. Herein, the recent advances of the important soil sensors in agricultural applications, in...

Soft crawling robots have attracted great attention due to their anticipated effective interactions with humans and uncertain environments, as well as their potential capabilities of completing a variety of tasks encompassing search and rescue, infrastructure inspection, surveillance, drug delivery, and human assistance. Herein, a comprehensive survey on recent advances of soft crawling robots categorized by their major actuation mechanisms is provided, including pneumatic/hydraulic pressure, chemical reaction, and soft active material‐based actuations, which include dielectric elastomers, shape memory alloys, magnetoactive elastomers, liquid crystalline elastomers, piezoelectric materials, ionic polymer–metal composites, and twisted and coiled polymers. For each type of actuation, the prevalent modes of locomotion adopted in representative robots, the design, working principle and performance of their soft actuators, and the performance of each locomotion approach, as well as the advantages and drawbacks of each design are discussed. This review summarizes the state‐of‐the‐art progresses and the critical knowledge in designing soft crawling robots and offers a guidance and insightful outlook for the future development of soft robots.

temperature sensors, [10] light emitting diodes, [11] radio frequency devices, [12] field effect transistors, [13] epidermal electronics, [2] and integrated circuits. [4] To integrate these stretchable electronics into a power-independent stretchable system in an elegant way, stretchable energy conversion/storage devices become of paramount importance. [14][15][16][17] Although over the decades, stretchable energy conversion devices like organic solar cells, [6] triboelectric nanogenerators, [18] and various piezoelectric devices [19] have been of great interest, energy storage devices such as electrochemical supercapacitors (SCs) have also been intensively explored for various applications. Their unique features of fast chargedischarge rate, high power density, long operation life, and modest energy excellently complement batteries. [17,20] However, most of the existing stretchable supercapacitors can only be stretched in one direction, whereas retaining functionality during multidirectional stretching is essential for many applications. Moreover, many of the stretchable SCs are affected by the applied strains, and are easily damaged if unexpected stretching happens to be larger than the predefined stretchability of the device in fabrication. [21] Among the available materials, carbon-based nanomaterials have been extensively utilized for stretchable SC electrodes due to their high specific surface area, structural integrity, and low cost. [14,17,22] For example, Yu et al. presented stretchable Stretchable supercapacitors have received increasing attention due to their broad applications in developing self-powered stretchable electronics for wearable electronics, epidermal and implantable electronics, and biomedical devices that are capable of sustaining large deformations and conforming to complicated surfaces. In this work, a new type of highly stretchable and reliable supercapacitor is developed based on crumpled vertically aligned carbon nanotube (CNT) forests transferred onto an elastomer substrate with the assistance of a thermal annealing process in atmosphere environment. The crumpled CNT-forest electrodes demonstrated good electrochemical performance and stability under either uniaxial (300%) or biaxial strains (300% × 300%) for thousands of stretching-relaxing cycles. The resulting supercapacitors can sustain a stretchability of 800% and possess a specific capacitance of 5 mF cm −2 at the scan rate of 50 mV s −1 . Furthermore, the crumpled CNT-forest electrodes can be easily decorated with impregnated metal oxide nanoparticles to improve the specific capacitance and energy density of the supercapacitors. The approach developed in this work offers an alternative strategy for developing novel stretchable energy devices with vertically aligned nanotubes or nanowires for advanced applications in stretchable, flexible, and wearable electronic systems.

Food quality monitoring, particularly, the detection of bacterial pathogens and spoilage throughout the food supply chain, is critical to ensure global food safety and minimize food loss. Incorporating sensors into packaging is promising, but it is challenging to achieve the required sampling volume while using food‐safe sensor materials. Here, by leveraging water‐based processing of silk fibroin, a platform for the detection of pathogenic bacteria in food is realized using a porous silk microneedle array; the microneedle array samples fluid from the interior of the food by capillary action, presenting the fluid to polydiacetylene‐based bioinks printed on the backside of the array. Through the colorimetric response of bioink patterns, Escherichia coli contamination in fish fillets is identified within 16 h of needle injection. This response is distinct from spoilage measured via the increase in sample pH. It is also shown that the microneedles can pierce commercial food packaging, and subsequently sample fluid and present it to the sensor, enabling the adaptation of the technology downstream in food supply chains such as in stores or at home. This study highlights that regenerated structural biopolymers can serve as safe materials for food contact and sensing with robust mechanical properties and tailored chemistry.

The precise deployment of functional payloads to plant tissues is a new approach to help advance the fundamental understanding of plant biology and accelerate plant engineering. Here, the design of a silk‐based biomaterial is reported to fabricate a microneedle‐like device, dubbed “phytoinjector,” capable of delivering a variety of payloads ranging from small molecules to large proteins into specific loci of various plant tissues. It is shown that phytoinjector can be used to deliver payloads into plant vasculature to study material transport in xylem and phloem and to perform complex biochemical reactions in situ. In another application, it is demonstrated Agrobacterium ‐mediated gene transfer to shoot apical meristem (SAM) and leaves at various stages of growth. Tuning of the material composition enables the fabrication of another device, dubbed “phytosampler,” which is used to precisely sample plant sap. The design of plant‐specific biomaterials to fabricate devices for drug delivery in planta opens new avenues to enhance plant resistance to biotic and abiotic stresses, provides new tools for diagnostics, and enables new opportunities in plant engineering.

Bistable mechanical systems having two local minima of potential energy can rest in either of the two stable equilibrium states in the absence of external loadings. A snap-through action may occur under suitable stimuli and/or loading, during which such systems exhibit distinct properties from linear structures. Such kinds of structures have been widely exploited for designing advanced functional systems for a variety of applications. Here, the advances of bistable structures are summarized for novel advanced functional systems, including actuators, energy harvesters, microelectromechanical systems (MEMS), robotics, energy absorbers, and programmable devices as well as metamaterials. The controllable snap-through motions are highlighted in the nonlinear structures of bistability/multistability. Finally, the major principles, structures, pros and cons, and the future research directions along with its challenges are discussed.