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Abstract Recently, many studies have investigated additive manufacturing (AM) of hierarchical surfaces with high surface area/volume (SA/V) ratios, and their performance has been characterized for applications in next-generation functional devices. Despite recent advances, it remains challenging to design and manufacture high SA/V ratio structures with desired functionalities. In this study, we established the complex correlations among the SA/V ratio, surface structure geometry, functionality, and manufacturability in the two-photon polymerization (TPP) process. Inspired by numerous natural structures, we proposed a 3-level hierarchical structure design along with the mathematical modeling of the SA/V ratio. Geometric and manufacturing constraints were modeled to create well-defined three-dimensional hierarchically structured surfaces with a high accuracy. A process flowchart was developed to design the proposed surface structures to achieve the target functionality, SA/V ratio, and geometric accuracy. Surfaces with varied SA/V ratios and hierarchy levels were designed and printed. The wettability and antireflection properties of the fabricated surfaces were characterized. It was observed that the wetting and antireflection properties of the 3-level design could be easily tailored by adjusting the design parameter settings and hierarchy levels. Furthermore, the proposed surface structure could change a naturally hydrophilic surface to near-superhydrophobic. Geometrical light trapping effects were enabled and the antireflection property could be significantly enhanced (> 80% less reflection) by the proposed hierarchical surface structures. Experimental results implied the great potential of the proposed surface structures for various applications such as microfluidics, optics, energy, and interfaces. 

Developing intelligent wearable energy storage devices that can endure harsh conditions is of interest for emerging applications in next‐generation electronics. Despite recent success in exploring functional materials for sophisticated self‐adaptivity in energy storage devices, it remains challenging to obtain both high reliability and superior performance. Herein, a novel method for fabricating micropatterned wearable thermoresponsive supercapacitors via direct ink writing (DIW) technique is reported. Thermal runaway of typical electrochemical storage devices with high power delivery capability can cause serious safety problems. The proposed temperature‐dependent structure works as self‐protection against the common thermal runaway issues of electrochemical energy storage devices. Such construction provides an automatic adjustment as high as 8 F g⁻¹in specific capacitance, resulting in an overall heat reduction by up to 40%. The printing resolution of the electrodes (175 µm) is among the best in recently reported planar carbon‐based energy storage devices by DIW technique. Manufacturing‐related parameters such as time‐dependent printing speed and curing temperature are also investigated to fabricate this integrated design with varied materials and accuracy. This strategy shows tremendous promise for future intelligent energy storage devices.

 

Proper distribution of thermally conductive nanomaterials in polymer batteries offers new opportunities to mitigate performance degradations associated with local hot spots and safety concerns in batteries. Herein, a direct ink writing (DIW) method is utilized to fabricate polyethylene oxide (PEO) composite polymers electrolytes (CPE) embedded with silane‐treated hexagonal boron nitride (S‐hBN) platelets and free of any volatile organic solvents. It is observed that the S‐hBN platelets are well aligned in the printed CPE during the DIW process. The in‐plane thermal conductivity of the printed CPE with the aligned S‐hBN platelets is 1.031 W⁻¹K⁻¹, which is about 1.7 times that of the pristine CPE with the randomly dispersed S‐hBN platelets (0.612 W⁻¹K⁻¹). Thermal imaging shows that the peak temperature (°C) of the printed electrolytes is 24.2% lower than that of the CPE without S‐hBN, and 10.6% lower than that of the CPE with the randomly dispersed S‐hBN, indicating a superior thermal transport property. Lithium‐ion half‐cells made with the printed CPE and LiFePO₄cathode displayed high specific discharge capacity of 146.0 mAh g⁻¹and stable Coulombic efficiency of 91% for 100 cycles at room temperature. This work facilitates the development of printable thermally‐conductive polymers for safer battery operations.

 

While 3D printing of rechargeable batteries has received immense interest in advancing the next generation of 3D energy storage devices, challenges with the 3D printing of electrolytes still remain. Additional processing steps such as solvent evaporation were required for earlier studies of electrolyte fabrication, which hindered the simultaneous production of electrode and electrolyte in an all‐3D‐printed battery. Here, a novel method is demonstrated to fabricate hybrid solid‐state electrolytes using an elevated‐temperature direct ink writing technique without any additional processing steps. The hybrid solid‐state electrolyte consists of solid poly(vinylidene fluoride‐hexafluoropropylene) matrices and a Li⁺‐conducting ionic‐liquid electrolyte. The ink is modified by adding nanosized ceramic fillers to achieve the desired rheological properties. The ionic conductivity of the inks is 0.78  × 10⁻³S cm⁻¹. Interestingly, a continuous, thin, and dense layer is discovered to form between the porous electrolyte layer and the electrode, which effectively reduces the interfacial resistance of the solid‐state battery. Compared to the traditional methods of solid‐state battery assembly, the directly printed electrolyte helps to achieve higher capacities and a better rate performance. The direct fabrication of electrolyte from printable inks at an elevated temperature will shed new light on the design of all‐3D‐printed batteries for next‐generation electronic devices.