•3D printed bioinspired tapered tubes based on observations of barnacles are designed.•The mechanical properties of the tubes under quasi-static compression loads are studied experimentally, ...numerically and theoretically.•The effects of the number of corrugations and the corrugation amplitudes on the structural deformation and energy absorption performance are obtained.•The crashworthiness of the corrugated tapered tubes under oblique loads is investigated.
Thin-walled structures are widely used as energy absorption devices in vehicles. This paper designs bioinspired thin-walled structures based on observations of barnacles and studies the mechanical properties of these structures under quasi-static conditions. The effects of the number of corrugations and the corrugation amplitudes on the structural deformation and energy absorption performance of 3D printed bioinspired tapered tubes are studied experimentally, numerically, and theoretically. The results show that the corrugation amplitude and the number of corrugations have a significant influence on the energy absorption parameters, and the specific energy absorption (SEA) can be significantly improved when the number and amplitude of the corrugations are properly controlled. The highest SEA of the corrugated tapered tube can be improved by 15.75% compared with the traditional tapered tube. Furthermore, the crashworthiness of the corrugated tapered tubes under oblique loads is also investigated. The result shows that the SEA of the corrugated tapered tube is 41.56% higher than that of the cylindrical tube when the oblique loading angle is 20°. Finally, the energy absorption performance of the multicell structures is studied, and they perform much better than conventional structures. Especially, the SEA of the multicell tapered tube with 16 cells is approximately 1.97 times that of conventional tube.
High-resolution visuotactile sensors are often bulky and have flat contact shapes, making it difficult to integrate into dexterous multifinger fingertips and perform manipulation tasks smoothly. In ...this article, we present a soft, low-cost, biomimetic fingertip-sized visuotactile sensor, which can perceive high-precision 3-D surface deformation. This novel sensor, named GelStereo BioTip, adopts stereo vision system to robustly acquire 3-D deformation information on multicurvature contact surfaces. In particular, a self-calibrating refractive stereo ray tracing modeling method is proposed to solve the problem of ray refraction on multimedium and multicurvature refractive surfaces in the binocular reconstruction system. GelStereo BioTip has an overall spatial resolution of 1.2 mm, a shape measurement accuracy of less than 0.28 mm over a range of 0-5 mm for numerous distinct contacts with varying contact area. We integrate the bionic fingertips into a dexterous robotic hand for validation, and the proposed bionic fingertip concept can be seamlessly transferred to a variety of robotic manipulators.
Graphene reinforced copper matrix composites (Gr/Cu) were fabricated by electrostatic self-assembly and powder metallurgy. The morphology and structure of graphene oxide, graphene oxide-Cu powders ...and Gr/Cu composites were characterized by scanning electronic microscopy, transmission electronic microscopy, X-ray diffraction and Raman spectroscopy, respectively. The effects of graphene contents, applied loads and sliding speeds on the tribological behavior of the composites were investigated. The results indicate that the coefficient of friction of the composites decreases first and then increases with increasing the graphene content. The lowest friction coefficient is achieved in 0.3 wt% Gr/Cu composite, which decreases by 65% compared to that of pure copper. The coefficient of friction of the composite does not have significant change with increasing the applied load, however, it increases with increasing the sliding speed. The tribological mechanisms of the composite under different conditions were also investigated.
In this study, the quasi-static compression performance of tapered tubes was investigated using finite element simulations. Previous studies have shown that a thickness gradient can reduce the ...initial peak force and that lateral corrugation can increase the energy absorption performance. Therefore, two kinds of lateral corrugated tapered tubes with variable thicknesses were designed, and their deformation patterns, load displacement curves, and energy absorption performance were analyzed. The results showed that when the thickness variation factor (k) was 0.9, 1.2, and 1.5, the deformation mode of the single corrugated tapered tube (ST) changed from transverse expansion and contraction to axial progressive folding. In addition, the thickness gradient design improved the energy absorption performance of the ST. The energy absorption (EA) and specific energy absorption (SEA) of the model with k = 1.5 increased by 53.6% and 52.4%, respectively, compared with the ST model with k = 0. The EA and SEA of the double corrugated tapered tube (DT) increased by 373% and 95.7%, respectively, compared with the conical tube. The increase in the k value resulted in a significant decrease in the peak crushing force of the tubes and an increase in the crushing force efficiency.
Molybdenum diselenide (MoSe2) nanosheets thin film gas sensor was firstly fabricated and its sensing potential to ppm-level ethanol vapor at low operating temperature was investigated. Ultrathin ...MoSe2 nanosheets were prepared in large scale through a facile liquid-phase exfoliation method using low-boiling-temperature solvent. The exfoliated MoSe2 nanosheets exhibited high purity and crystallinity with few atomic layer thickness. Systematical gas sensing tests demonstrated that MoSe2 nanosheets based thin film could be utilized as ethanol gas sensor with linear response, quick recovery, and good repeatability at 90 °C. The sensing mechanism of MoSe2 toward ethanol was investigated based on first principle calculation. The adsorption behavior of ethanol molecules on MoSe2 surface was revealed in light of adsorption orientation, adsorption energy, charge transfer, projected electronic density of state, and molecular orbital. The calculation well matched with experimental results. It is found the quick and completed recovery of MoSe2 nanosheets sensor was benefited by the appropriate physical interaction between ethanol and MoSe2 surface. This finding offers a competitive option instead of conventional graphene sensor for ethanol gas detection at low temperature.
Hybrid organic switch-inorganic semiconductor systems have important applications in both photo-responsive intelligent surfaces and microfluidic devices. In this context, herein, we performed ...first-principles calculations to investigate a series of organic switches of trans/cis-azobenzene fluoride and pristine/oxidized trimethoxysilane adsorbed on low-index anatase slabs. The trends in the surface–adsorbate interplay were examined in terms of the electronic structures and potential distributions. Consequently, it was found that the cis-azobenzene fluoride (oxidized trimethoxysilane)-terminated anatase surface attains a lower ionization potential than the trans-azobenzene fluoride (pristine trimethoxysilane)-terminated anatase surface due to its smaller induced (larger intrinsic) dipole moment, whose direction points inwards (outwards) from the substrate, which originates from the electron charge redistribution at the interface (polarity of attached hydroxyl groups). By combining the induced polar interaction analysis and the experimental measurements in the literature, we demonstrate that the ionization potential is an important predictor of the surface wetting properties of adsorbed systems. The anisotropic absorbance spectra of anatase grafted with azobenzene fluoride and trimethoxysilane are also related to the photoisomerization and oxidization process under UV irradiation, respectively.
Hybrid organic switch-inorganic semiconductor systems have important applications in both photo-responsive intelligent surfaces and microfluidic devices. In this context, herein, we performed ...first-principles calculations to investigate a series of organic switches of
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-azobenzene fluoride and pristine/oxidized trimethoxysilane adsorbed on low-index anatase slabs. The trends in the surface-adsorbate interplay were examined in terms of the electronic structures and potential distributions. Consequently, it was found that the
-azobenzene fluoride (oxidized trimethoxysilane)-terminated anatase surface attains a lower ionization potential than the
-azobenzene fluoride (pristine trimethoxysilane)-terminated anatase surface due to its smaller induced (larger intrinsic) dipole moment, whose direction points inwards (outwards) from the substrate, which originates from the electron charge redistribution at the interface (polarity of attached hydroxyl groups). By combining the induced polar interaction analysis and the experimental measurements in the literature, we demonstrate that the ionization potential is an important predictor of the surface wetting properties of adsorbed systems. The anisotropic absorbance spectra of anatase grafted with azobenzene fluoride and trimethoxysilane are also related to the photoisomerization and oxidization process under UV irradiation, respectively.
The humid adhesive of the concrete protecting coatings has been a common problem and faces challenges in underground, ocean, bridge and tunnel engineering, and its adhesive mechanisms of humid ...interface with cementitious materials have little scientific backing. In this study, the bionic composite coatings based on biomass polyurethane were fabricated by utilizing catechol chemistry of mussels and coordination crosslinking strategy for enhancing the humid adhesive properties. The environmentally benign biomass polyurethane (PU) derived from epoxidized soybean oil were synthesized by the prepolymerization method through hydroxylation and stepwise polymerization. The chemical grafting of dopamine (DA) combined with coordination crosslinking of Mn2+ strategy was employed for the composite modification of the Biomass PU. The effect of molar ratios of DA and Mn2+ on the tensile and thermal properties, water resistance, crystallinity, UV aging, molecular structure, morphology of the Biomass PU and its adhesive strength with cementitious materials were investigated. The pull-off testing results show that the optimum dry and humid adhesive strength between the coating and cementitious materials are 9.08 MPa and 9.47 MPa respectively when the molar ratio of DA/Mn2+ is 2:1, which increases by 29.34 % and 90.93 % compared with pristine biomass PU. The synergistic effect of catechol moieties and Mn2+ in enhancing the cross-linking and promoting the hydration film drainage combined with interfacial interaction has been demonstrated. These insights can be feasible for designing high performance polymer coatings with excellent humid adhesive properties and also can boost the development of biomimetic science in concrete protecting and repairing.
•A novel Mussel-bionic and biomass polyurethane coating•Catechol chemistry and coordination crosslinking strategy for enhancing humid adhesive properties•Synergistic effect of catechol and Mn2+ was demonstrated.•This strategy boosts the development of biomimetic science in concrete protecting and repairing.
We obtained mono- or few-layer Ti2VC2Tx nanosheets by etching (top). The Ti2VC2Tx sensors exhibited excellent gas-sensitive performance for ammonia at room temperature, with remarkable responsivity ...(bottom left), and excellent selectivity (bottom right).
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•First study on NH3 detection capability of Ti2VC2Tx at room temperature.•Demonstrated Ti2VC2Tx sensor's excellent sensing performance to NH3.•Elucidated Ti2VC2Tx's selectiveness of NH3 via first-principles calculations.
Double-transition-metal (DTM) MXenes are potentially multifunctional materials with greater compositional and structural tunability than mono-transition-metal (MTM) MXenes, enabling controllable formation of defects and controllable tuning of material properties. Herein, we investigate Ti2VC2Tx's ammonia gas sensing via experiments and theoretical calculations. Ti2VC2Tx exhibited a notable response, exceeding 25 %, to 100 ppm ammonia at room temperature with rapid response/recovery times of 4 s/16.2 s. Furthermore, the Ti2VC2Tx sensor shows exceptional ammonia selectivity, attributed to closer adsorption distances and higher adsorption energies of ammonia molecules. This study broadens the application area of DTM MXenes and further demonstrates the potential of MXene materials for gas sensing.
