Good Mechanical Robustness Research Articles

Highly Sensitive Torsion Sensor Based on Side-Hole-Fiber Sagnac Interferometer

A highly sensitive torsion sensor based on side-hole fiber (SHF) Sagnac interferometer is proposed and experimentally demonstrated in this paper. The theoretical analyses on sensing performances of the proposed interferometric sensor are in good accordance with their experimental measurement counterparts. Due to photo-elastic effect, the birefringence of SHF in the loop would vary with the torsional rate, giving rise to linear wavelength shift and sinusoidal power variation responses to torsion applied on the SHF. Based on the wavelength and intensity interrogations of transmission dips, the torsional sensitivities reach up to about 2.2 nm/(rad/m) and ±10 dB/(rad/m), respectively. Opposite wavelength shift responses for clockwise and counterclockwise torsion states equip the proposed sensor with good twisting direction distinguishability. Besides, the experimental results indicate that our proposed sensor has a low axial strain cross sensitivity of 4.3 pm/με. The side-hole-fiber-based interferometric torsion sensor possesses such desirable merits as high sensitivity, low axial strain cross sensitivity, good torsional direction distinguishability, and good mechanical robustness, ensuring its viability for practical use on torsion sensing occasions.

A Novel Icephobic Strategy: The Fabrication of Biomimetic Coupling Micropatterns of Superwetting Surface

AbstractThis work proposes a biphilic icephobic surface by combining the top‐down and bottom‐up methods. It is found that the impacting droplet on biphilic surface is divided into several parts during the recoiling process, which can significantly reduce the drop contact time before freezing. The anti‐icing test of the biphilic surface in the simulated environment also proves its excellent icephobic capacity. At one aspect, the freezing delay time on biphilic surface is positively correlated with the pillar diameters and negatively correlates with the distance of adjacent pillars. At another aspect, the stress concentrator at the edge between the superhydrophobic area and superhydrophilic area results in the dramatic reduction of ice adhesion strengths. In the real environment test, substantial particle ice is found on the biphilic surface. Different from the glaze ice and rime ice, the particle ice has a smaller contact area with the surface and is easier to be removed. Furthermore, the as‐prepared biphilic surface possesses good mechanical robustness and a long lifespan in the cyclic icing/melting test. It is shown that the new class of nonwetting surfaces presented here can be useful for anti/deicing applications in the future.

Crosslinked Hydrogel Capsules for Cell Encapsulation Formed Using Amino/Betaine Dual-Functional Semibatch Copolymers

Robust hydrogel capsules consisting of calcium alginate beads with shells reinforced via crosslinked amino/betaine copolymers of N-(3-aminopropyl) methacrylamide hydrochloride (APM) with 2-methacryloyloxyethyl phosphorylcholine (MPC) are described. These capsules are designed to support future use in immunoisolation of therapeutic cells for transplant purposes. The poly[APM-co-MPC] copolymers were prepared by semibatch free radical copolymerization to reduce the significant compositional drift and the resulting diffusional spread within alginate beads, observed for analogous batch copolymers. Fluorescent labeling was used to track copolymer distribution within the alginate hydrogels. Semibatch copolymers led to better shell confinement and lower cationic charge density on the capsule surface. Three reagents were used to covalently cross-link the resulting poly(amino/betaine) shells: cationic tetrakis(hydroxymethyl)phosphonium chloride (THPC), charge-neutral genipin and anionic partially hydrolyzed poly(methyl vinyl ether-alt-maleic anhydride) (PMM50). Genipin-crosslinked capsules were found to be remarkably robust in pipet aspiration tests. Selected capsules were exposed to FITC-labeled bovine serum albumin to assess the relative degree of protein adhesion, as a proxy for immune recognition; genipin crosslinked capsules were found to have very low levels of BSA binding and good mechanical robustness.

Biomimetic Turbinate-like Artificial Nose for Hydrogen Detection Based on 3D Porous Laser-Induced Graphene.

Inspired by the turbinate structure in the olfaction system of a dog, a biomimetic artificial nose based on 3D porous laser-induced graphene (LIG) decorated with palladium (Pd) nanoparticles (NPs) has been developed for room-temperature hydrogen (H2) detection. A 3D porous biomimetic turbinate-like network of graphene was synthesized by simply irradiating an infrared laser beam onto a polyimide substrate, which could further be transferred onto another flexible substrate such as polyethylene terephthalate (PET) to broaden its application. The sensing mechanism is based on the catalytic effect of the Pd NPs on the crystal defect of the biomimetic LIG turbinate-like microstructure, which allows facile adsorption and desorption of the nonpolar H2 molecules. The sensor demonstrated an approximately linear sensing response to H2 concentration. Compared to chemical vapor-deposited (CVD) graphene-based gas sensors, the biomimetic turbinate-like microstructure LIG-gas sensor showed ∼1 time higher sensing performance with much simpler and lower-cost fabrication. Furthermore, to expand the potential applications of the biomimetic sensor, we modulated the resistance of the biomimetic LIG sensor by varying laser sweeping gaps and also demonstrated a well-transferred LIG layer onto transparent substrates. Moreover, the LIG sensor showed good mechanical flexibility and robustness for potential wearable and flexible device applications.

Mechanically robust hydrophobic bio-based epoxy coatings for anti-corrosion application

Corrosion of aluminum and its alloys causes serious problems to our daily life. As a common method for corrosion protection, epoxy resin has been widely used as the coating material due to its easy processability and excellent properties. However, its high water absorption and brittleness, as well as the usage of volatile organic solvents during coating preparation, has limited its applications in some areas. In this study, we reported an environmentally friendly hydrophobic coating based on bio-epoxy using water as the only solvent during the preparation. The coating was fabricated by introducing superhydrophobic SiO2 nanoparticles, a hydrophobic curing agent, and hexadecyltrimethoxysilane into an isosorbide-based epoxy resin via a one-step spin coating process. The coating exhibits high hydrophobicity with a water contact angle (CA) of 134 ± 3°. This as-prepared coating is found to have good mechanical robustness against sands erosion: it maintained a high water repellence with the CA of 146 ± 2° after sands erosion for 30 s. In addition, the as-obtained coating shows a one-order of magnitude reduction in the corrosion current density (Jcorr), a positive shift of the corrosion potential (Ecorr) from −1.008 V to −0.747 V, and an inhibition efficiency of 92%.

Pd Nanoparticle Film on a Polymer Substrate for Transparent and Flexible Hydrogen Sensors.

Alongside the rise in fully automated equipment and wearable devices, there is currently a high demand for optically transparent and flexible gas sensors operating at room temperature. Nanoparticle films are ideal H2-sensing materials that can be coupled with flexible substrates because of their discrete nanogranular structure and unique interparticle electrical responsiveness. In this work, we present an optically transparent and flexible H2 sensor based on a Pd nanoparticle film, prepared on a polyethylene terephthalate sheet using a straightforward nanocluster deposition technique. Hundreds of bending cycles demonstrated that the sensor has good electrical stability and mechanical robustness without significant degradation in H2-sensing performance. The H2-sensing behaviors under bent state were systematically evaluated. The loading of tensile and compressive strains under bent state produced a positive and negative influence, respectively, on the sensing performances. The possible influence mechanism of the tensile and compressive strains on the H2-sensing performance was attributed to the changes in the percolation network topology and the interparticle space induced by the strains. The ability to detect a H2 concentration as low as 15 ppm, dynamic response range as wide as 0-10%, and sub-10 s response time was achieved. In addition, the sensor can be operated in the relative humidity range of 0-90% at room temperature. These results demonstrate that the sensor exhibits significant potential for next-generation transparent and flexible H2 detectors.

Fabrication of superhydrophobic coatings on cotton fabric using ultrasound-assisted in-situ growth method

A highly durable superhydrophobic cotton fabric was fabricated via an ultrasound-assisted in situ growth method. The morphology and the component of the superhydrophobic coating on cotton fabric were characterized by SEM and FT-IR, respectively. The as-prepared superhydrophobic cotton fabric shows liquid repellency for common household liquids, outstanding stability in deionized water, various solvents, strong acidic/alkali solution, and boiling water, and good mechanical robustness after sandpaper abrasion test. Furthermore, the fabric coating shows both superhydrophobic and superoleophilic properties simultaneously with a high water contact angle of 154 ± 0.5°. Thus, the as-prepared superhydrophobic cotton fabric can be used to separate the oil/water mixtures (e.g., n-hexane, n-heptane, dodecane, and kerosene) and the separation efficiency was more than 96%. In addition, the obtained fabric maintains good reusability after 50 separation cycles with above 97% of the separation efficiency for the both dodecane/water and n-heptane/water mixture. The as-prepared fabric coating shows high separation efficiency, stable recyclability, and better durability, which can be used in oil spill accidents for oil/water separation.

Superhydrophobic modified-polyurethane coatings for bushing of power transformers: From material to fabrication, mechanical and electrical properties

The presence of dust and coastal salt water found in a high moisture content environment can affect the stability of bushings in power transformers. This problem leads to transformer shut down and in severe conditions it can cause transformer expulsion. To eliminate this problem, a superhydrophobic modified-polyurethane coating was fabricated that contained easy cleaning property. Final coating had contact angles higher than 150° and CAH (Contact Angle Hysteresis) less than 10 degrees. The coating indicated good UV durability and mechanical robustness which was investigated by an abrasion test. It could pass acid rain and dry lightning impulse voltage tests. The best results were attained with the formulation containing 8 wt% nanosilica.

Robust, self-cleaning, amphiphobic coating with flower-like nanostructure on micro-patterned polymer substrate

Many superhydrophobic surfaces lose their repellency to water owing to the contamination of organic liquids or mechanical damage. Though amphiphobic coatings can repel both water and organic liquids, the poor mechanical and chemical stabilities significantly restrict their practical applications. Herein, we demonstrated a hydrothermal method to synthesize micro-patterned substrates bearing NiAl layered double hydroxide with flower-like nanostructures, which resemble the surface morphology of a lotus leaf. The surface was further modified by a low-surface-energy material of perfluorooctanoic acid through a solution immersion method. The binder-free coating formed in-situ on the substrate showed a good adhesion quality of 5B (ASTM D-3359). The coating possessed high repellency to different liquid droplets, including water, diiodomethane, ethylene glycol, soybean oil, etc., with surface tensions ranging from 72.7 to 22.4 mN m−1. Due to the excellent self-cleaning property, the contaminant on the surface was easily cleaned as the water droplet rolled off. Moreover, the coating exhibited good mechanical and chemical robustness in some extreme conditions, such as gas blowing, sea sand abrasion, and chemical immersion tests. These good performances made the coating possible to be applied widely in various practical applications.

Solid-state yet flexible supercapacitors made by inkjet-printing hybrid ink of carbon quantum dots/graphene oxide platelets on paper

Paper-based flexible supercapacitors (SCs) show advantages due to the improved adhesion between paper and active materials, the simplified printing process and the lower cost, compared to other substrates such as plastics. Here we report the fabrication of solid-state yet flexible SCs by inkjet-printing a hybrid ink consisting of carbon quantum dots (CQDs) and graphene oxide (GO) platelets, followed by casting of polyvinyl alcohol (PVA)/sulfuric acid (H2SO4) gel electrolyte. The SC obtained from 100-time-printing of the hybrid ink shows a specific capacitance of ~1.0 mF cm−2 at a scan rate of 100 mV s−1, which is enhanced by nearly 150%; the whole device including paper substrate, gel electrolyte and active material demonstrates an energy density of 0.078 mW h cm−3 at a power density of 0.28 mW cm−3. In addition, the excellent mechanical strength of GO platelets ensures the good flexibility and mechanical robustness of the printed SCs, which show a retention of 98% in capacitance after being bended for 1,000 cycles at a bending radius of 7.6 mm. This study demonstrates a promising strategy for the large-scale preparation of low-cost, lightweight, and flexible/wearable energy storage devices based on carbon-based ink and paper substrate.

The effects of morpholine pre-treated and carboxymethylated cellulose nanofibrils on the properties of alginate-based hydrogels

The effects of varying percentage loadings of morpholine pre-treated cellulose nanofibrils (MCNF) and carboxymethylated cellulose nanofibrils (CMCNF) on the aqueous swelling, compressive modulus and viscoelastic properties of calcium-ion-crosslinked alginate hydrogels were investigated. In addition, the pore structures of hydrogels with the highest compressive modulus were studied. The incorporation of 5 wt. % MCNF resulted in a slightly reduced aqueous swelling, a 36% increase in compressive modulus and a layered pore structure when compared with the neat alginate hydrogel. On the other hand, the addition of CMCNF at the same loading led to a slightly improved aqueous swelling, an increase in compressive modulus (17%) and high porosity. Further increases in CNF loadings did not result in significant increase in material properties. The alginate/CNF composite materials have potentials to be used in applications where good swelling and mechanical robustness are required.

Ru2P Nanoparticle Decorated P/N-Doped Carbon Nanofibers on Carbon Cloth as a Robust Hierarchical Electrocatalyst with Platinum-Comparable Activity toward Hydrogen Evolution

It is desirable yet challenging to develop highly active and durable hydrogen evolution reaction (HER) electrocatalysts with Pt-comparable activity for future energy devices. In this work, we report Ru2P nanoparticle decorated P/N dual-doped carbon nanofibers on carbon cloth (Ru2P@PNC/CC-900) as a highly efficient and durable hierarchical HER electrocatalyst in both acidic and alkaline media. Electrochemical tests show that this Ru2P@PNC/CC-900 possesses Pt-comparable HER activity to support 10 mA cm–2 HER current density at low overpotential of 15 and 50 mV in acidic and alkaline condition, respectively. Density functional theory calculations reveal that coupling Ru2P nanoparticles with heteroatom-doped carbon fibers leads to enhanced intrinsic HER activity. The integrative hierarchical architecture further endows high surface areas with good mechanical robustness to support abundant catalytically active sites and possesses excellent electrical conductivity and efficient access for mass transportation to...

Crosslinkable deoxidizing hybrid adhesive of epoxy–diacid for electrical interconnections in semiconductor packaging

AbstractFor electrical interconnections in semiconductor packaging, epoxy‐based pastes have recently attracted considerable interest due to their excellent adhesion to various substrates and their reasonable electrical and mechanical properties, especially when combined with deoxidizing agents (to remove metallic oxides). Here, epoxy–diacid‐based hybrid pastes were examined to achieve a deoxidizing capability for eliminating Sn‐based solder oxides and adhesion between microchip and substrate as a one‐step process. Onset, exothermic peak and end temperatures of the reaction between epoxy and diacids were systematically probed using DSC, rheometry and Fourier transform infrared (FTIR) spectroscopy. The last moment of the adhesive reaction during heating substantially enhanced the thermal and mechanical properties of the epoxy–diacid adhesive despite the absence of exothermic enthalpy detected by DSC. The glass transition temperature (Tg) and Young's modulus gradually decreased as a function of aliphatic chain length of diacids except when the length was extremely short and voids were produced. Soldering (wetting) and deoxidizing capabilities of the hybrid adhesive were observed via optical microscopy and FTIR. The correlation between the reaction, Tg, conversion and viscosity was also investigated. Lastly, complete wetting and electrical interconnection with good mechanical robustness were achieved for a commercial chip/substrate set by flip‐chip bonding. © 2018 Society of Chemical Industry

All-organic superhydrophobic coatings with mechanochemical robustness and liquid impalement resistance.

Superhydrophobicity is a remarkable evolutionary adaption manifested by several natural surfaces. Artificial superhydrophobic coatings with good mechanical robustness, substrate adhesion and chemical robustness have been achieved separately. However, a simultaneous demonstration of these features along with resistance to liquid impalement via high-speed drop/jet impact is challenging. Here, we describe all-organic, flexible superhydrophobic nanocomposite coatings that demonstrate strong mechanical robustness under cyclic tape peels and Taber abrasion, sustain exposure to highly corrosive media, namely aqua regia and sodium hydroxide solutions, and can be applied to surfaces through scalable techniques such as spraying and brushing. In addition, the mechanical flexibility of our coatings enables impalement resistance to high-speed drops and turbulent jets at least up to ~35 m s-1 and a Weber number of ~43,000. With multifaceted robustness and scalability, these coatings should find potential usage in harsh chemical engineering as well as infrastructure, transport vehicles and communication equipment.

Highly Sensitive and Wearable In2O3 Nanoribbon Transistor Biosensors with Integrated On-Chip Gate for Glucose Monitoring in Body Fluids.

Nanoribbon- and nanowire-based field-effect transistor (FET) biosensors have stimulated a lot of interest. However, most FET biosensors were achieved by using bulky Ag/AgCl electrodes or metal wire gates, which have prevented the biosensors from becoming truly wearable. Here, we demonstrate highly sensitive and conformal In2O3 nanoribbon FET biosensors with a fully integrated on-chip gold side gate, which have been laminated onto various surfaces, such as artificial arms and watches, and have enabled glucose detection in various body fluids, such as sweat and saliva. The shadow-mask-fabricated devices show good electrical performance with gate voltage applied using a gold side gate electrode and through an aqueous electrolyte. The resulting transistors show mobilities of ∼22 cm2 V-1 s-1 in 0.1× phosphate-buffered saline, a high on-off ratio (105), and good mechanical robustness. With the electrodes functionalized with glucose oxidase, chitosan, and single-walled carbon nanotubes, the glucose sensors show a very wide detection range spanning at least 5 orders of magnitude and a detection limit down to 10 nM. Therefore, our high-performance In2O3 nanoribbon sensing platform has great potential to work as indispensable components for wearable healthcare electronics.

Directional torsion and temperature discrimination based on a multicore fiber with a helical structure.

We propose and experimentally demonstrate a directional torsion sensor based on a Mach-Zehnder interferometer formed in a multicore fiber (MCF) with a ~570-μm-long helical structure (HS). The HS was fabricated into the MCF by simply pre-twisting and then heating with a CO2 laser splicing system. This device shows the capability of directional torsion measurement from -17.094 rad/m to 15.669 rad/m with the sensitivity of ~0.118 nm/(rad/m). Moreover, since the multiple interferences respond differently to torsion and temperature simultaneously, the temperature cross-sensitivity of the proposed sensor can be eliminated effectively. Besides, the sensor owns other merits such as easy fabrication and good mechanical robustness.

Structurally colored polymer films with narrow stop band, high angle-dependence and good mechanical robustness for trademark anti-counterfeiting.

The photonic stop bands of colloidal crystals appear as structural colors, which are potentially useful for display devices, colorimetric sensors, optical filters, paints, and photonic papers. However, low durability and pale colors caused by the undesired scattering of light seriously limit their practical applications. In this article, a polydimethylsiloxane (PDMS)/photonic crystal (PC)/PDMS sandwich structure was designed as a free standing structural colored film with good durability and brilliant color. The monodispersed polystyrene (PS) spheres were self-assembled on the hydrophobic PDMS surface to facilitate the integrity of the assembled structure and then, PDMS with a refractive index of 1.41 was filled in the gaps between the PS spheres (nPS = 1.59), replacing air (nair = 1). The surface was finally covered with a thin layer of PS PCs, forming a continuous and free standing PC film. The continuous feature of the composite PC can greatly improve their mechanical properties. At the same time, the lower index contrast results in narrow reflection peaks for the composite films, which indicates that higher color purity and brightness could be achieved. Clearly distinguished, vivid structural colors can be observed between red to green or green to blue by tuning the viewing angle from 5° to 50° for films composed of PS spheres with diameters of 247 nm or 209 nm, respectively. They can also be easily patterned by spraying methods and embedded as a trademark on clothes. Patterns with different structural colors at different angle can be clearly be observed under sunlight, which makes them potentially useful as security materials.

Hierarchically Porous Graphene/ZIF-8 Hybrid Aerogel: Preparation, CO2 Uptake Capacity, and Mechanical Property.

A hierarchical zeolitic imidazole framework (ZIF) combining a micropore with a mesoporous structure is desirable to enhance mass transport and gives rise to novel applications. Here, hierarchically porous graphene/ZIF-8 hybrid aerogel (GZAn) materials were successfully prepared by a two-step reduction strategy and a layer-by-layer assembly method. To avoid a tedious dry step and the use of an energy-consuming freeze-drying technology, a reduced graphene oxide hydrogel with different reduction degrees was chosen as a template to grow ZIF-8 crystals in situ. The parameter of density and elemental analysis was adopted to calculate the amount of ZIF-8 in GZAn materials for different assembly cycles. The distribution of micropores and mesopores of GZAn materials was controlled by changing the loading of ZIFs in GZAn materials. Furthermore, GZA8 materials showed enhanced CO2 uptake capacity (0.99 mmol g-1, 298 K, 1 bar) than pure ZIF-s crystals and pure graphene aerogels, showing an excellent synergistic effect of hierarchical pore structures. Meanwhile, with the increase of ZIF-8 loading, the mechanical robustness of GZAn was uplifted obviously. This work provides an efficient method to prepare hierarchically porous ZIFs-based materials with good CO2 uptake capacity and tunable mechanical robustness.

Synthesis of three-dimensional porous reduced graphene oxide hydrogel/carbon dots for high-performance supercapacitor

A composite composed of reduced graphene oxide hydrogel/carbon dots (rGH/CDs) is prepared hydrothermally. The composite has a three-dimensional (3D) interconnected network structure and exhibits good electrical conductivity and mechanical robustness, making it ideal electrode materials in supercapacitors. The carbon dots (CDs) in the reduced graphene oxide hydrogel promotes electron transport and reduces the internal resistance and charge transfer resistance in addition to providing a large surface area. The flexible solid-state supercapacitor comprising the 130μm thick rGH/CDs electrode delivers excellent performance including high gravimetric specific capacitance of 264Fg−1 (up to 301Fg−1 for a 40μm thick electrode), areal specific capacitance of 394mFcm−2 (up to 432Fcm−2 for a 200μm thick electrode), excellent cycling stability (9.1% deterioration after 5000cycles), larger energy density (35.3Whkg−1), as well as high power density (516Wkg−1). This study demonstrates the tremendous potential of rGH/CDs in high-performance flexible energy storage devices.

Superhydrophobic coating with multiscale structure based on crosslinked silanized polyacrylate and nanoparticles

To obtain a superhydrophobic surface with hierarchical micro/nanostructures, two kinds of SiO2 nanoparticles with different sizes were embedded into crosslinked silanized polyacrylate (CPSA). The silanized polyacrylate (PSA) was first synthesized via free radical copolymerization of acrylate monomers and vinyltrimethoxysilane (VTMS). Then, the silicone methoxyls of the VTMS units were subsequently crosslinked by a condensation reaction with hydroxy terminated polydimethylsiloxane (HTPDMS) to form CPSA. The structure of PSA and CPSA were characterized by Fourier transform infrared spectroscopy. The surface wetting property, surface morphology, mechanical robustness and anticorrosion performance of the CPSA/SiO2 coatings were systematically studied. The results demonstrated that the obtained coatings could be expediently sprayed onto substrates to create a water-repellent surface, and possessed good mechanical robustness and high corrosion resistance against NaCl solutions.