Self-assembly of graphene oxide flakes for smart and multifunctional coating with reversible formation of wrinkling patterns.

One of the main purposes of smart and multifunctional coatings is to have the versatility to be applied in a wide range of applications. However, the functions of smart materials are often highly limited. In particular, the stimuli-responsive lateral expansion of coatings based on 2D materials has not been reported before. This manuscript describes small two-dimensional graphene oxide (GO) flakes (e.g., thin sheets with a thickness of a few nanometers and much larger lateral dimensions) that act as elementary agents for the formation of smart and multifunctional coatings. The coating can be self-assembled from the GO flakes and disassembled flexibly when required. The coating is stimuli-responsive: upon localized contact with water, it expands and forms wrinkling patterns throughout its whole surface. Evaporating the water allows the wrinkles to disappear; hence, the process is reversible. This stimuli-responsiveness can be controlled to be reduced or completely switched off by temperature or pressure. These features are fundamentally due to the reversible intermolecular interactions among the flakes and favorable packing structure of the coating. The smart coating is shown to be useful for patterned fluidic systems of the desired shapes and the development of channels between fluidic reservoirs via the shortest path. Importantly, these results showed that a simple collection of uniquely 2D elementary agents with small nanoscale thickness can self-assemble into macroscopic materials that perform interactive and multifunctional operations.

Ultracompact and multifunctional integrated photonic platform.

Realizing a multifunctional integrated photonic platform is one of the goals for future optical information processing, which usually requires large size to realize due to multiple integration challenges. Here, we realize a multifunctional integrated photonic platform with ultracompact footprint based on inverse design. The photonic platform is compact with 86 inverse designed-fixed couplers and 91 phase shifters. The footprint of each coupler is 4 µm by 2 µm, while the whole photonic platform is 3 mm by 0.2 mm-one order of magnitude smaller than previous designs. One-dimensional Floquet Su-Schrieffer-Heeger model and Aubry-André-Harper model are performed with measured fidelities of 97.90 (±0.52) % and 99.34 (±0.44) %, respectively. We also demonstrate a handwritten digits classification task with the test accuracy of 87% using on-chip training. Moreover, the scalability of this platform has been proved by demonstrating more complex computing tasks. This work provides an effective method to realize an ultrasmall integrated photonic platform.

Metallization of 3D Printed Polymers and Their Application as a Fully Functional Water-Splitting System.

In this work, the plating of high-quality amorphous nickel-phosphorous coating with low resistivity of 0.45 µΩ m (298 K) on complex 3D printed polymeric structures with high uniformity is reported. Such a polymer metallization results in an effective conductivity of 4.7 × 104 S m-1. This process also allows flexible structures to maintain their flexibility along with the conductivity. Octet-truss structures with nickel-iron-(oxo) hydroxide nanosheets electrodeposited onto further displays excellent water-splitting performance as catalytic electrodes, i.e., in KOH (1 m, aq), a low oxygen evolution reaction (OER) overpotential of 197 mV at 10 mA cm-2 and Tafel slope of 51 mV dec-1. Using this light-weight electrode with high specific area, strength, and corrosion resistance properties, a fully functional water-splitting system is designed and fabricated through the concentric integration of 3D printed components. A dense polymeric mesh implemented is also demonstrated as an effective separator of hydrogen and oxygen bubbles in this system.