Lotus Leaf-Inspired Breathable Membrane with Structured Microbeads and Nanofibers.

Electrospinning is a feasible technology to fabricate nanomaterials. However, the preparation of nanomaterials with controllable structures of microbeads and fine nanofibers is still a challenge, which hinders widespread applications of electrospun products. Herein, inspired by the micro/nanostructures of lotus leaves, we constructed a structured electrospun membrane with excellent comprehensive properties. First, micro/nanostructures of membranes with adjustable microbeads and nanofibers were fabricated on a large scale and quantitatively analyzed based on the controlling preparation, and their performances were systematically evaluated. The deformation of diverse polymeric solution droplets in the electrospinning process under varying electric fields was then simulated by molecular dynamic simulation. Finally, novel fibrous membranes with structured sublayers and controllable morphologies were designed, prepared, and compared. The achieved structured membranes demonstrate a high water vapor transmission rate (WVTR) > 17.5 kg/(m2 day), a good air permeability (AP) > 5 mL/s, a high water contact angle (WCA) up to 151°, and a high hydrostatic pressure of 623 mbar. The disclosed science and technology in this article can provide a feasible method to not only adjust micro/nanostructure fibers but also to design secondary multilayer structures. This research is believed to assist in promoting the diversified development of advanced fibrous membranes and intelligent protection.

Tunable Thermochromic Graphene Metamaterials with Iridescent Color.

Thermochromic materials have been widely applied in energy-efficient buildings, aerospace, textiles, and sensors. Conventional thermochromic materials rely on material phase or structure changes upon thermal stimuli, which only enable a few colors, greatly limiting their applicability. Here, we propose and demonstrate the concept of dynamically tunable thermochromic graphene metamaterials (TGMs), which can achieve continuous color tunability (380-800 nm) with fast (<100 ms) response times. The TGMs are composed of an ultrathin graphene oxide (GO) film on a flexible metal substrate. We demonstrated that external thermal energy can dynamically adjust the water contents in the GO film to manipulate the color of TGMs. An impressive thermochromic sensitivity of 1.11 nm/°C covering a large percentage of the color space has been achieved. Prototype applications for a cup and smartphone have been demonstrated. The reversible TGMs promise great potential for practical applications of temperature sensing in optoelectronic devices, environmental monitoring, and dynamic color modulation.

Evolving Strategies for Producing Multiscale Graphene-Enhanced Fiber-Reinforced Polymer Composites for Smart Structural Applications.

Graphene has become an important research focus in many current fields of science including composite manufacturing. Developmental work in the field of graphene-enhanced composites has revealed several functional and structural characteristics that promise great benefits for their use in a broad range of applications. There has been much interest in the production of multiscale high-performance, lightweight, yet robust, multifunctional graphene-enhanced fiber-reinforced polymer (gFRP) composites. Although there are many reports that document performance enhancement in materials through the inclusion of graphene nanomaterials into a matrix, or its integration onto the reinforcing fiber component, only a few graphene-based products have actually made the transition to the marketplace. The primary focus of this work concerns the structural gFRPs and discussion on the corresponding manufacturing methodologies for the effective incorporation of graphene into these systems. Another important aspect of this work is to present recent results and highlight the excellent functional and structural properties of the resulting gFRP materials with a view to their future applications. Development of clear standards for the assessment of graphene material properties, improvement of existing materials and scalable manufacturing technologies, and specific regulations concerning human health and environmental safety are key factors to accelerate the successful commercialization of gFRPs.

A Field Study Into Hong Kong's Wet Markets: Raised Questions Into the Hygienic Maintenance of Meat Contact Surfaces and the Dissemination of Microorganisms Associated With Nosocomial Infections.

Millions every day purchase their raw meat in wet markets around the globe, especially in Hong Kong city, where modern and a traditional way of living is made possible. While food hygiene standards in Hong Kong have more recently focused on the safety of meat sold in these wet markets, the hygienic surface level of wooden cutting boards used for processing meats is seldom observed. This original study performed microbial community profiling, as well as isolating and identifying various strains multiple wooden cutting boards from nine wet markets located on Hong Kong Island. Our study also investigated the efficiency of scraping the surface of cutting boards as a traditional cleaning technique in Hong Kong. Results indicate that these hygienic practices are inefficient for guarantying proper surface hygiene as some most tested cutting boards were found to harbor microbial species typically associated with hospital nosocomial infections, such as Klebsiella pneumoniae. Further analysis also led to discovering the presence of antibiotic-resistant genes (ARGs) among isolated strains. Our results showcase the significance and effects of cross-contamination in Hong Kong wet markets, especially with regards to the potential spreading of clinically-relevant strains and ARGs on food processing surfaces. This study should, therefore, serve as a basis to review current hygienic practices in Hong Kong's wet market on a larger scale, thereby improving food safety and ultimately, public health.

Large dynamic range pressure sensor based on two semicircle-holes microstructured fiber.

This paper presents a sensitive and large dynamic range pressure sensor based on a novel birefringence microstructured optical fiber (MOF) deployed in a Sagnac interferometer configuration. The MOF has two large semicircle holes in the cladding and a rectangular strut with germanium-doped core in the center. The fiber structure permits surrounding pressure to induce large effective index difference between the two polarized modes. The calculated and measured group birefringence of the fiber are 1.49 × 10-4, 1.23 × 10-4, respectively, at the wavelength of 1550 nm. Experimental results shown that the pressure sensitivity of the sensor varied from 45,000 pm/MPa to 50,000 pm/MPa, and minimum detectable pressure of 80 Pa and dynamic range of better than 116 dB could be achieved with the novel fiber sensor. The proposed sensor could be used in harsh environment and is an ideal candidate for downhole applications where high pressure measurement at elevated temperature up to 250 °C is needed.

Characterisation of recycled mixed plastic solid wastes: Coupon and full-scale investigation.

In Australia, the plastic solid waste (PSW) comprises 16% by weight of municipal solid waste but only about one-fourth are recycled. One of the best options to increase the recycling rate of mixed PSW is to convert them into products suitable for construction. However, a comprehensive understanding on the mechanical behaviour of mixed PSW under different loading conditions is important for their widespread use as a construction material. This study focuses on investigating the mechanical behaviour of recycled mixed PSW containing HDPE, LDPE and PP using coupon and full-scale specimens. From coupon test, the strength values were found to be 14.8, 19.8, 20, 5.6MPa in tension, compression, flexure and shear respectively, while the modulus of elasticity are 0.91, 1.03, 0.72GPa in tension, compression and flexure respectively. The coefficient of variance of the measured properties for coupon and fullscale specimens was less than 10% indicating that consistent material properties can be obtained for mixed PSW. More importantly, the strength properties of mixed PSW are comparable to softwood structural timber. The flexural behaviour of full-scale specimens was also predicted using fibre model analysis and finite element modelling. Comparison showed that using coupon specimen's properties, the flexural behaviour of the full-scale specimens can be predicted reliably which can eliminate the costly and time consuming arrangements for full-scale experimental tests.

Electrochemical performance of a graphene-polypyrrole nanocomposite as a supercapacitor electrode.

A unique nanoarchitecture has been established involving polypyrrole (PPy) and graphene nanosheets by in situ polymerization. The structural aspect of the nanocomposite has been determined by Raman spectroscopy. Atomic force microscopy reveals that the thickness of the synthesized graphene is ∼ 2 nm. The dispersion of the nanometer-sized PPy has been demonstrated through transmission electron microscopy and the electrochemical performance of the nanocomposite has been illustrated by cyclic voltammetry measurements. Graphene nanosheet serves as a support material for the electrochemical utilization of PPy and also provides the path for electron transfer. The specific capacitance value of the nanocomposite has been determined to be 267 F g(-1) at a scan rate of 100 mV s(-1) compared to 137 mV s(-1) for PPy, suggesting the possible use of the nanocomposite as a supercapacitor electrode. After 500 cycles, only 10% decrease in specific capacitance as compared to initial value justifies the improved electrochemical cyclic stability of the nanocomposite.

Extraction of mechanical properties of foot plantar tissues using ultrasound indentation associated with genetic algorithm.

This paper demonstrates the use of ultrasound indentation technique for estimating the mechanical properties of foot plantar tissues in virtue of the reconstruction of the force response using genetic algorithm (GA) from an indentation test based on a quasi-linear viscoelastic (QLV) model. The indentation test on the plantar tissues covering the right first metatarsal head of a normal subject was carried out to verify the feasibility of the GA for the extraction of the tissue properties. The QLV properties of the plantar tissues were determined by the GA with a fixed Poisson's ratio. Such results were then compared with those obtained using a classical optimization method. Moreover, the GA was further employed to simultaneously determine the QLV properties as well as the Poisson's ratio of the plantar tissues. The correlations between the QLV properties and the Poisson's ratio are discussed.

Formation and growth mechanism of dissimilar coiled carbon nanotubes by reduced-pressure catalytic chemical vapor deposition.

Dissimilar coiled carbon nanotubes were prepared by catalytic chemical vapor deposition (CCVD) on finely divided Co nanoparticles supported on silica gel under reduced pressure and at lower gas flow rates. The morphology of the regular coiled carbon nanotubes were examined by TEM, while the polygonization characteristics of the helix were examined by SAED. Observations were made on other forms of irregular coils with various shapes by TEM. On the basis of the heptagon-pentagon construction theory, we proposed a helix formation mechanism, which involves a carbon core formation centering on a catalytic particle followed by carbon helices growth controlled by kinetics.