Large-Scale, Abrasion-Resistant, and Solvent-Free Superhydrophobic Objects Fabricated by a Selective Laser Sintering 3D Printing Strategy.

Manufacturing abrasion-resistant superhydrophobic matters is challenging due to the fragile feature of the introduced micro-/nanoscale surface roughness. Besides the long-term durability, large scale at meter level, and 3D complex structures are of great importance for the superhydrophobic objects used across diverse industries. Here it is shown that abrasion-resistant, half-a-meter scaled superhydrophobic objects can be one-step realized by the selective laser sintering (SLS) 3D printing technology using hydrophobic-fumed-silica (HFS)/polymer composite grains. The HFS grains serve as the hydrophobic guests while the sintered polymeric network provides the mechanical strength, leading to low-adhesion, intrinsic superhydrophobic objects with desired 3D structures. It is found that as-printed structures remained anti-wetting capabilities even after undergoing different abrasion tests, including knife cutting test, rude file grinding test, 1000 cycles of sandpaper friction test, tape test and quicksand impacting test, illustrating their abrasion-resistant superhydrophobic stability. This strategy is applied to manufacture a shell of the unmanned aerial vehicle and an abrasion-resistant superhydrophobic shoe, showing the industrial customization of large-scale superhydrophobic objects. The findings thus provide insight for designing intrinsic superhydrophobic objects via the SLS 3D printing strategy that might find use in drag-reduce, anti-fouling, or other industrial fields in harsh operating environments.

Neuron-Inspired Soft Robot Teams and Their Non-Contact Electric Signal Transmission Based on Electromagnetic Induction.

Transmission of electric signal among robots enables them to construct a team to behave beyond capabilities of the individuals. However, such a signal transmission is elusive so far for soft robots due to the employment of soft materials, rather than traditionally rigid electronic units. In this study, we demonstrate neuron-inspired soft robots (NISRs) with an electromagnetic induced signal transmission system. The prototype 15-cm-long NISRs can not only be moved driven by a manually moving magnet but also transmit signals to others in a noncontact type based on the electromagnetic induction through their tentacle units. Owing to the motion and special signal transmission mode, three NISRs can form diverse signal transport pathways to light up light emitting diodes in different positions. Furthermore, an alternative current (AC) signal can be generated when applying an interval loading/unloading compressive force with the velocity of 800 mm·min-1 on the head of NISR integrated a magnet and a coil (named it NISR-plus). Such an AC signal can be immediately sensed by neighboring NISRs, indicating the construction of a signal transmission network among the NISR team. Our results open perspectives to realize signal transmission of soft robots via wireless electromagnetic induction and favor the development of soft robot teams.

Active Perception in Non-Visual Recognition Environments by Stretchable Tentacle Sensor Arrays.

Smoke fog or other light-interference environments have intrinsic obstruction for visual recognition techniques to explore objects and surroundings. Alternatively, tactile perceptions, rather than visual observations, are commonly used by burrowing or deep-sea animals to communicate with environments. Bio-inspired by this natural wisdom, here, we demonstrate stretchable tentacle sensor arrays, which can recognize surrounding objects located in non-visual conditions such as smoke fog or dark environment. Each tentacle sensor is composed of two functional parts: a retractable tentacle with a magnetic top and an elastomer bottom containing copper coils. Different from traditionally passive tactile sensors, these tentacle sensors can actively stretch under the control of a syringe pump, yielding different electrical signals when in contact with the objects. Analyzing collected sensing signals of those tactile sensor arrays by the feature analysis model, complex morphological information of irregular objects in the smoke fog can be recognized. Our study reveals a fundamental connection between stretchable tactile sensors and feature analysis and demonstrates its practical potential for active perception in a non-visual recognition environment.

Efficient degradation of tetracycline in wide pH range using MgNCN/MgO nanocomposites as novel H2O2 activator.

Currently existing Fenton-like catalysts were limited in wastewater treatment owing to their potential transition-metal poisoning, narrow applicable pH range and high dependence on external energy excitation. In this work, the MgNCN/MgO nanocomposites were firstly synthesized by a facile one-pot calcination of melamine and basic magnesium carbonate, and used as novel H2O2 activator for antibiotic removal. It was found that the MgNCN/MgO composite calcined at 550°C with the mass ratio of melamine to basic magnesium carbonate at 2:1, exhibited an excellent catalytic ability to tetracycline (TC) degradation in a wide pH range of 4-10 without any external energy input. More than 90% of TC (100 mL, 50 mg/L) could be degraded within 30 min by 10 mg of the nanocomposite in the presence of 0.2 mL of 30 wt% H2O2. Based on the experimental results, it was concluded that the Mg-N coordination between MgNCN and MgO in MgNCN/MgO nanocomposites activated H2O2 to produce primary singlet oxygen (1O2) and minor hydroxyl radicals (·OH), responding for TC degradation. In addition, the degradation pathways of TC were deduced by determining the generated intermediates during the degradation process. This work provided a novel idea for designing transition-metal-free catalysts for nonradical activation of H2O2 in the absence of external energy excitation.

Facile one-step synthesis of 3D hierarchical flower-like magnesium peroxide for efficient and fast removal of tetracycline from aqueous solution.

Hierarchically three dimensional (3D) flower-like magnesium peroxide (MgO2) nanostructures were synthesized through a facile one-step precipitation method. The effects of magnesium salt, reaction temperature, precipitant and surfactant on the morphology and structure of MgO2 were systematically investigated. The as-obtained samples using magnesium sulfate, ammonia and trisodium citrate were composed of 3D flowers assembled by numerous nanosheets, and SO42- played a vital role in the formation of flower-like nanostructures. The 3D flower-like MgO2 possessed high active oxygen content of 24.10 wt% and large specific surface area of 385 m2/g. Ten mg of flower-like MgO2 could efficiently degrade 90 % of tetracycline (TC) within 60 min under stirring condition. ESR tests and radical quenching experiments suggested that hydroxyl radicals were crucial for TC degradation. Moreover, the column filled with flower-like MgO2 could quickly and efficiently eliminate TC with the assistance of air flow, and the degradation efficiency almost had no decrease even after twenty consecutive runs. Significantly, the concentrations of magnesium and iron ions dissolved in the filtrate from the column were far below the limits of drinking water standards. Additionally, the possible degradation pathways of TC were also proposed according to the determination of generated intermediates during the degradation process.

Enhanced dark adsorption and visible-light-driven photocatalytic properties of narrower-band-gap Cu2S decorated Cu2O nanocomposites for efficient removal of organic pollutants.

The Cu2S-decorated Cu2O nanocomposites were synthesized by a facile co-precipitation and calcination method, and used as adsorbent and photocatalyst to remove organic pollutants from wastewater. Batch adsorption experiments were conducted to investigate the influences of molar ratio of Cu2O to Cu2S, initial solution pH, coexisting anion and temperature on the adsorption performances. As-obtained Cu2O/Cu2S-9/1 nanocomposite with high specific surface area (45.88 m2/g) exhibited superior adsorption ability towards Congo red, methyl orange and tetracycline in aqueous solution. The adsorption of organics onto the nanocomposite was a spontaneous and exothermic process, and the adsorption processes could be well described by the Freundlich isothermic and Pseudo-second-order kinetic models. The Cu2O/Cu2S-9/1 nanocomposite also showed excellent photocatalytic degradation activities for organic pollutants. Optical properties characterization suggested that the decoration of Cu2S could effectively enhance visible-light absorption and inhibit the recombination of photo-generated electron-hole pairs. ESR tests and trapping experiments of reactive species indicated that both superoxide radicals (O2-) and holes (h+) were crucial for the photocatalytic degradation of organic pollutants. Moreover, the photocatalytic efficiency of Cu2O/Cu2S-9/1 nanocomposite had no significant decrease even after four consecutive runs. The bifunctional nanocomposite as adsorbent and photocatalyst presents a great potential in treating organic-contaminated wastewater.