Elastomeric materials display a complicated set of stretchability and fracture properties that strongly depend on the flaw size, which has long been of interest to engineers and material scientists. Here, we combine experiments and numerical simulations for a comprehensive understanding of the nonlocal, size-dependent features of fracture in elastomers. We quantitatively describe the size-dependent fracture behavior using a nonlocal continuum model. The key ingredient of the nonlocal model is the use of an intrinsic length scale associated with a finite fracture process zone, which is inferred from experiments. Of particular importance, our experimental and theoretical approach passes the critical set of capturing the key aspects of the size-dependent fracture in elastomers. Applications to a wide range of synthetic elastomers that exhibit moderate (∼100%) to extreme stretchability (∼1000%) are presented, which is also used to demonstrate the applicability of our approach in elastomeric specimens with complex geometries.

Herein, a mild thermal annealing (MTA) process is presented for additive-free gelation of graphene oxide (GO) dispersions. This process transitions the GO from a nematic liquid crystal phase to a random network structure, significantly enhancing its rheological properties by order of magnitude. This transition is facilitated by the diffusion of functional groups on the GO surface, which induces hydrophobic attractions, leading to a stable network structure. Employing rheo-SAXS experiments, detailed insights are provided into the microstructural changes of GO gel under shear stress, establishing a direct correlation between its rheological behavior and microstructure. The distinctive properties of MTA-processed inks are illustrated, seamlessly integrating with 3D printing, to yield a highly porous lattice structure that demonstrates promising potential as a supercapacitor electrode. The MTA process, an additive-free approach to gelation, maintains the inherent dispersion properties of GO while offering scalability. Thus, this method brings significant economic and environmental advantages compared to conventional gelation techniques. The findings not only advance the fundamental understanding of 2D colloidal network gels but also increase the potential of GO for a wide range of applications, from gas and liquid absorbers to electrodes for energy storage and conversion, and biomedical fields. 

 The energy devices for generation, conversion, and storage of electricity are widely used across diverse aspects of human life and various industry. Three-dimensional (3D) printing has emerged as a promising technology for the fabrication of energy devices due to its unique capability of manufacturing complex shapes across different length scales. 3D-printed energy devices can have intricate 3D structures for significant performance enhancement, which are otherwise impossible to achieve through conventional manufacturing methods. Furthermore, recent progress has witnessed that 3D-printed energy devices with micro-lattice structures surpass their bulk counterparts in terms of mechanical properties as well as electrical performances. While existing literature focuses mostly on specific aspects of individual printed energy devices, a brief overview collectively covering the wide landscape of energy applications is lacking. This review provides a concise summary of recent advancements of 3D-printed energy devices. We classify these devices into three functional categories; generation, conversion, and storage of energy, offering insight on the recent progress within each category. Furthermore, current challenges and future prospects associated with 3D-printed energy devices are discussed, emphasizing their potential to advance sustainable energy solutions. 

  Additive manufacturing, or 3D printing attracts growing attention as a promising method for creating functionally graded materials. Fused deposition modeling (FDM) is widely available, but due to its simple process, creating spatial gradation of diverse properties using FDM is challenging. Here, we present a 3D printed digital material filament that is structured towards 3D printing of functional gradients, utilizing only a readily available FDM printer and filaments. The DM filament consists of multiple base materials combined with specific concentrations and distributions, which are FDM printed. When the DM filament is supplied to the same printer, its constituent materials are homogeneously blended during extrusion, resulting in the desired properties in the final structure. This enables spatial programming of material properties in extreme variations, including mechanical strength, electrical conductivity, and color, which are otherwise impossible to achieve with traditional FDMs. Our approach can be readily adopted to any standard FDM printer, enabling low-cost production of functional gradients. 

 This paper presents a material-efficient multimaterial projection micro-stereolithography (PμSL), a digital light processing (DLP) additive manufacturing process for printing microstructures. We present a droplet-based resin supply system to address the issue of excessive material waste of the multimaterial PμSL. By depositing droplets of different liquid resins, 3D printing of a microstructure can still be performed without the need for a traditional vat while printing materials can be switched with minimal material consumption. Precise control of small droplet volume is obtained by pressure control of the resin injection nozzles, exact opening times of fluid valves, and appropriate surface coatings in order to portion droplets so that just enough material is brought to the build area. Since PμSL enables micro 3D printing (in-plane resolution of 76 μm), PμSL using droplet-based resin supply module provides multimaterial micro 3D printing with low material consumption. Also reported is that material bleeding, which degrades the printing resolution during multimaterial printing, can be minimized by using a cleaning droplet system. We present 3D printing of highly complex multimaterial 3D microstructures using three different photocurable polymers, demonstrating a material efficiency of 11.4%, which is 500 times higher than that of a previously reported PμSL process using dynamic fluidic control.