The advent of 3D printing brought about the possibilities of microlattice metamaterials as advanced materials with the potentials to surpass the functionalities of traditional materials. Sound absorbing materials which are also tough and lightweight are of particular importance as practical engineering materials. There are however a lack of attempts on the study of metamaterials multifunctional for both purposes. Herein, we present four types of face‐centered cubic based plate and truss microlattices as novel metamaterials with simultaneous excellent sound and mechanical energy absorption performance. High sound absorption coefficients nearing 1 and high specific energy absorption of 50.3 J g−1 have been measured. Sound absorption mechanisms of microlattices are proposed to be based on a “cascading resonant cells theory”, an extension of the Helmholtz resonance principle that we have conceptualized herein. Characteristics of absorption coefficients are found to be essentially geometry limited by the pore and cavity morphologies. The excellent mechanical properties in turn derive from both the approximate membrane stress state of the plate architecture and the excellent ductility and strength of the base material. Overall, this work presents a new concept on the specific structural design and materials selection for architectured metamaterials with dual sound and mechanical energy absorption capabilities.

unattended to, prolonged exposure leads to acute and chronic health hazards and complications such as hearing loss, cardiovascular diseases, cognitive impairment, etc. [1] Sound absorbing materials hence find widespread adoption in a diverse range of applications. For reference, the market value for acoustic materials has been constantly increasing and it is projected to be 16 billion U.S. dollars in 2025, nearly doubling that in 2015. [2] Traditional and commercial sound absorbers in the market have always been focused on foams, fibrous materials, fabric, and perforated panels. [3] However, limitations of the traditional absorbers exist, for instance, such as non-optimal designs, lack of structural rigidity, and health hazards (from synthetic fibers), etc. As such, increasing research efforts have been placed on the investigations of new materials and new meta-structures for novel and better performing sound absorbers. [4] Several examples of new materials investigated as sound absorbers include graphene-based foams, [5] shape memory foams, [6] window foams, [7] and aerogels. [8] However, material-based absorbers compare generally pale in performance to structure-based ones under similar specifications (e.g., thickness, target frequency). Further, such materials also usually lack the rigidity of structures and some may also pose potential health hazards. In turn, structure-based absorbers are more robust and notable successes have been achieved with superior absorption capabilities and broadened absorption range shown. Examples of novel absorbing structures investigated include the Fabry-Perot channel assembly, [9] planar coiled tubes, [10] perforated composite resonators, [11] membrane structures, [12] and shrinking duct structures, [13] etc. Despite the success, the mentioned examples nonetheless are still limited to a structural level-they lack the design flexibilities for an overall system or product.As such, it would be of high research interests to design absorbers based on the principles of structural designs, but yet to down-scale them to a size domain in the range of materials. The advent of additive manufacturing (AM) in the recent years has brought about such possibilities. Apart from being an effective rapid-prototyping tool and a viable manufacturing Noise pollution is a highly detrimental daily health hazard. Sound absorbers, such as the traditionally used perforated panels, find widespread applications. Nonetheless, modern product designs call for material novelties with enhanced performance and multifunctionality. The advent of additive manufacturing has brought about the possibilities of functional materials design to be based on structures rather than chemistry. With this in mind, herein, the traditional concept of perforated panels is revisited and is incorporated with additive manufacturing for the development of a novel microlattice-based sound absorber with additional impact resistance multifunctionality. The structurally optimized microlattice presents excellent broadband absorption with a...

The aggregation behavior of a fluorinated surfactant (FC-4) was studied by surface tension measurements in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4]) and hexafluorophosphate ([bmim][PF 6]) at various temperatures. A series of surface properties, including adsorption efficiency (p C 20), effectiveness of surface tension reduction (Pi CAC), maximum surface excess concentration (Gamma max) and minimum surface area/molecule (A(min)) at the air-water interface were estimated. By comparing the fluorinated surfactant with traditional surfactants, we deduced that the surface activity of the fluorinated surfactant in ILs was superior to the activity of other surfactants. From the CAC values and their temperature dependence, we estimated the thermodynamic parameters of aggregate formation. The thermodynamic parameters indicate that the aggregate of FC-4 in [bmim][BF 4] is a traditional micelle, while the aggregate of FC-4 in [bmim][PF 6] is nanodroplets composed of FC-4 molecules segregated from the solution phase. These results were further confirmed by (1)H NMR measurements.

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 × 10 4 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.

Fine control of the self-assembly of silicon species to hierachical materials has attracted research attention for many years. The mesostructures produced by such processes under weak acidic-basic conditions mimic bioenvironments are the focus of current research. In this study, mesoporous silicas with various novel morphologies such as mesoporous spheres, nanotubes, and oligomeric nanotubes have been systematically synthesized by using boric acid in the system, which is the key reagent for the fine control of the assembly of the silica precursors. The as-prepared materials are characterized using transmission electron microscopy (TEM), small-angle X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and nitrogen sorption measurements. The results support the assembly process of the nanomicelle of silica and surfactant under the conditions of boric acid, from which the synergistic weak interactions cause the morphology evolution of silicas. The current research provides effective information for understanding the formation of mesoporous silica under conditions mimicking biosilification processes.