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The iron and nitrogen co-doped porous carbon supported Au nanoparticle catalysts (Au/FeNPC) are synthesized via a facile pyrolysis method. The morphology, crystal structure, surface composition, and chemical state of the Au/FeNPC catalysts are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The catalytic performances of the Au/FeNPC for BH4− oxidation reaction (BOR) are investigated by cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP), and linear voltammetric sweep (LSV). Among the as-prepared Au/FeNPC catalysts, Au/FeNPC-40 catalyst possesses the highest catalytic activity for BOR, and the BOR peak current density on the Au/FeNPC-40 electrode is up to 45.4 mA cm−2 with the high transferred electron number of 7.0.

The electromigration (EM) damage is becoming a severe problem in the printed flexible electronics as the printed circuits are fabricated thinner and thinner due to the development of printing technology. In this work, the EM behavior of printed silver wires was investigated by EM experiments and numerical simulations. The EM tests showed that voids are generated in the cathode area and hillocks are formed in the anode area for a wire with a small length. However, with the increase of wire length, hillocks tend to occur on the two sides of the silver wire middle part. The results of numerical simulations based on the atomic flux divergence (AFD) method revealed that the formation of the hillocks on the printed wire is caused by not only the mechanism of electron wind but also the strong temperature gradient along the wire length and width direction. Also, it can be concluded that the temperature gradient induced by Joule heating plays a more important role than electron wind in the atomic migration of the printed silver wire subjected to a high current density. The influence of the printed silver wire size on the EM behavior was also analyzed by numerical simulation, and the results demonstrated that the printed silver wires with a larger length and a smaller width-to-thickness ratio are more likely to develop hillocks on the two sides of silver wire middle part while subjected to a high current density.

Purpose Soft grippers have safer and more adaptable human–machine and environment–machine interactions than rigid grippers. However, most soft grippers with single gripping postures have a limited gripping range. Therefore, this paper aims to design a soft gripper with variable gripping posture to enhance the gripping adaptability. Design/methodology/approach This paper proposes a novel soft gripper consisting of a conversion mechanism and four spring-reinforced soft pneumatic actuators (SSPAs) as soft fingers. By adjusting the conversion mechanism, four gripping postures can be achieved to grip objects of different shapes, sizes and weights. Furthermore, a quasi-static model is established to predict the bending deformation of the finger. Finally, the bending angle of the finger is measured to validate the accuracy of the quasi-static model. The gripping force and gripping adaptability are tested to explore the gripping performance of the gripper. Findings Through experiments, the results have shown that the quasi-static model can accurately predict the deformation of the finger; the gripper has the most significant gripping force under the parallel posture, and the gripping adaptability of the gripper is highly enhanced by converting the four gripping postures. Originality/value By increasing the gripping posture, a novel soft gripper with enhanced gripping adaptability is proposed to enlarge the gripping range of the soft gripper with a single posture. Furthermore, a quasi-static model is established to analyze the deformation of SSPA.

Carbon-supported Au-doped N-C-coated CoFe alloy nanocomposite electrocatalysts (Au/CoFe@CN/C) are prepared and applied to BH4− electrooxidation. The physical and electrochemical properties of the catalysts are characterized and tested by X-ray diffraction, transmission electron microscopy, cyclic voltammetry, chronamperometry, chronopotentiometry, and rotating disk electrode voltammetry. The results show that Au(50)/CoFe@CN(50)/C has excellent catalytic performance for BH4− electrooxidation, high charge transfer number up to 6.4, and low precious metal content, making it a promising anode electrocatalyst of direct borohydride fuel cell.

An N-doped carbon-coated Co2P-supported Au nanocomposite (Au/Co2P@NC/C) was synthesized via a facile pyrolysis procedure. The morphology and crystal structure of the Au/Co2P@NC/C catalyst were tested by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), and the electrocatalytic performances of Au/Co2P@NC/C for borohydride oxidation reaction (BOR) were evaluated by cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP), linear sweep voltammetry (LSV), and rotating disc electrode (RDE) voltammetry. Among the as-prepared Au/Co2P@NC/C catalysts, Au(50)Co2P@NC(50)/C exhibited the highest electrocatalytic activity for BOR. The BOR current density at −0.1 V on the Au(50)Co2P@NC(50)/C electrode was 48.4 mA cm−2, which is much higher than that on the Au/C electrode (24.8 mA cm−2).

ZIF-derived Co, N co-doped porous carbon-supported Au nanoparticles (Au/CoNPC) are synthesized via a novel facile pyrolysis method. The morphology, crystal structure, surface composition and chemical state of the Au/CoNPC composite catalysts are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The catalytic properties of Au/CoNPC for the borohydride oxidation reaction (BOR) are investigated by cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP), linear sweep voltammetry (LSV), and rotating disc electrode (RDE) voltammetry. Among the as-prepared catalysts, the Au/CoNPC-40 catalyst shows the highest catalytic activity for the BOR. The BOR peak current density on the Au/CoNPC-40 electrode is up to 48.4 mA cm−2 and the transferred electron number is up to 7.5.

Soft pneumatic actuators (SPAs) play an important role in leading the development of soft robotics. However, due to the inherent characteristics of soft materials, the low driving force limits the application of SPAs. This study presents a high-force soft pneumatic bending actuator (SPBA) that consists of a spring, an eccentric silicone cylinder, and a limiting fiber. Based on the Neo-Hookean model, a theoretical model is established to predict the relationship between the bending angle and the pressure of SPBA. Furthermore, we characterize the performance of SPBA in terms of the bending capability, tip force, as well as response time. The results demonstrate the effectiveness of the theoretical model, as well as the high tip force (10.2 N) and fast response capability of SPBA. Finally, SPBAs are used to construct a three-finger soft gripper. The load capacity of the gripper is proofed, which indicates that the gripping force of the gripper increases with the pressure of the fingers and the diameter of the object. The gripping test of the gripper is performed. The result shows that the gripper with the pinching mode can grip objects of various sizes and shapes in the air and underwater, and the gripper with enveloping mode can grip objects with weight up to 1.25 kg.

In this paper, carbon-supported nickel hydroxide-doped platinum (Pt/Ni(OH)2/C) nanocatalysts are synthesized by a two-step method, and the morphology and structure of Pt/Ni(OH)2/C are studied by transmission electron microscope and X-ray diffraction analysis. The electrocatalytic performance of the Pt/Ni(OH)2/C for borohydride oxidation reaction (BOR) is studied by using cyclic voltammetry, chronoamperometry, chronopotentiometry, and rotating disc electrode voltammetry. The Pt/Ni(OH)2/C catalysts show much better catalytic performance than Pt/C, and Pt(50)/Ni(OH)2(50)/C exhibits the best catalytic performance among all as-prepared Pt/Ni(OH)2/C catalysts. Moreover, the electron transfer number (n) related to BOR is evaluated, and n of 3.5 is achieved on Pt(50)/Ni(OH)2(50)/C electrode.

A new approach was put forward to identify the damage parameters of the shear modified GTN damage model proposed by Nahshon and Hutchinson (Eur J Mech Solid 27:10–17, 2008) by combining the artificial neural networks algorithm and small punch test. The factorial design method was used to analyze the influence of the parameters on the shape of load-displacement curve of small punch test. The less important parameters were set as empirical value and the significant factors were determined by an artificial neural networks model which was build up based on large amount of simulations of small punch tests with different levels of damage parameters values. The identified parameters were validated by small punch test simulations with different specimen thickness. The results show that the identified parameters of the shear modified GTN damage model are effective to characterize the mechanical behavior as well as the damage evolution and ductile failure of material during the process of small punch test. In addition, the applicability of the identified parameters in the tests with different stress condition were verified.

Carbon-supported Au modified N-doped carbon-coated FeMn alloy nanoparticle composites (Au/FeMn@CN/C) are prepared and used as electrocatalysts for BH4− electrooxidation. The surface morphology of the Au/FeMn@CN/C is observed using a transmission electron microscope and their composition is analyzed by X-ray diffraction. The results show that the prepared Au/FeMn@CN/C is a three-layer core–shell structure and the FeMn@CN nanosphere is coated with Au nanoparticles. The electrochemical performance of the prepared Au/FeMn@CN/C is studied by electrochemical tests, and the results show that Au(50)/FeMn@CN(50)/C shows the most excellent performance for direct BH4− electrooxidation which has more negative overpotential and an electrooxidation current density of up to 46.46 mA cm−2 with an electron-transfer number of 5.3.

Carbon supported Pd–Sn (Pd–Sn/C) nanoparticle electrocatalysts are prepared via a facile and environmentally friendly method and successfully applied in BH4− electrooxidation. Transmission electron microscopy results and X-ray diffraction results show that Pd–Sn nanocatalysts with a particle size of about 4 nm are uniformly distributed on the surface of a carbon black support without obvious agglomeration. Electrochemical results show that the catalytic activity of the Pd–Sn/C catalysts for BH4− electrooxidation is significantly higher than that of Pd/C. In particular, the Pd50Sn50/C catalyst has the highest electrocatalytic activity for BH4− electrooxidation among the four as-prepared catalysts. In addition, the BH4− electrooxidation reaction electron transfer number (n) of 3.9 was evaluated on the Pd50Sn50/C electrode.

A nitrogen-doped carbon-supported Au-modified NiFe alloy nanoparticle composite catalyst (Au/NiFe/N–C) has been prepared by a simple method and used as an electrocatalyst for the BH4− oxidation reaction (BOR). The physical and electrochemical properties of the as-prepared Au/NiFe/N–C catalyst have been tested by transmission electron microscopy, X-ray diffraction, cyclic voltammetry, chronoamperometry, chronopotentiometry, and rotating disk electrode voltammetry. The results showed that the catalytic activity of Au/NiFe/N–C for BOR was much higher than that of a carbon-supported Au nanocatalyst (Au/C); in particular, the Au(50)NiFe(50)/N–C catalyst demonstrated much higher catalytic activity with 2-fold higher peak current density than Au/C for BOR.

Flexible strain sensors that are currently available are mainly used in human motion recognition and medical health detection applications, and there is still an urgent need for sensors to realize real-time monitoring of the 3D deformation of industrial and agricultural products. In this work, a flexible strain sensor with a hat-shaped structure was fabricated using a molding technique to perform in situ measurement of 3D deformation. An algorithm for resistance change detection and linear calibration equations were proposed to enable analysis of the deformation data and calculation of local shape changes. The sensor was applied to monitor the growth deformation of a kumquat fruit, and the results were highly consistent with the algorithm. The proposed technique has great potential for application to 3D deformation detection of flexible objects.

A universal soft gripper for fruit grasping is challenging to develop. In this study, a modular and reconfigurable soft pneumatic gripper was designed. The designed gripper was inspired by the dexterous grasping of the human hand for fruits of different shapes and sizes. It comprised three soft extension actuators (SEAs), two soft rotation actuators (SRAs), and three soft bending actuators (SBAs). By adjusting SRAs, two grasping poses (claw and clenching pose) could be made to hold fruits of different shapes. The grasping size under each pose could be continuously adjusted by SEAs to grasp fruits of different sizes. SBAs were used to mimic soft fingers for grasping. Theoretical and simulation models were established to predict the relationships between deformations and pressures of SEAs, SRAs, and SBAs. The deformation characteristics of these actuators were experimentally investigated. It was shown that, by inflating SEAs, the grasping sizes under the claw and clenching poses could be increased by 87.5% and 94.5%, respectively. Furthermore, a visual recognition system was designed for automatically controlling the grasping pose and size. Grasping tests showed that, by reconfiguring the grasping pose and size, various fruits, vegetables, and foods with weights from 32 to 786 g (24.6 folds) and diameters from 30 to 141 mm (4.7 folds) could be successfully grasped, indicating the broad applicability of our all-pneumatic soft gripper.

A microwave-assisted two-steps method was proposed for the facile and fast preparation of silver nanoparticle conductive ink. The nanoparticles in the ink are of multi-sized, which is beneficial to getting higher packing density and better conductivity of the printed/written pattern. The effects of the reaction parameters of microwave and additives on the written pattern resistivity were studied on the basis of scanning electron microscope, X-ray diffraction and surface porosity results. Both of the microwave energy and the addition of PVP as the capping agent were found to be critical for the formation of face-centered cubic silver nanoparticles in the conductive ink. The surface porosity and the pore distribution form were also demonstrated to affect the pattern conductivity. The electrical resistivity or the pattern written with the ink prepared at microwave irradiation time of 90 s was calculated to be 364 μΩ cm. The second step of simple centrifugation process could improve the pattern conductivity effectively. After concentrated the conductive ink for two times, the electrical resistivity of the written pattern reduced from 364 to 77 μΩ cm. The proposed two-steps of microwave combined with centrifugation method is a simple and useful way for the preparation of silver nanoparticle conductive ink that can be used in printed electronics.

Various techniques have been developed to fabricate flexible sensors for applications in human-computer interaction and health monitoring. However, the accurate detection of 3D deformation using flexible sensors remains a challenge. In this study, a stretchable strain sensor with a hollow structure was developed for the dual-channel detection of 3D deformation. The sensor was fabricated using a molding technique and a mixture of graphene and Ecoflex and then coated with a layer of thermochromic material. The sensor was applied to detect the volume change of a sphere, and changes in the resistance and color of the sensor from Joule heating were simultaneously observed. The sensor has high detection accuracy and operational reliability and can be applied for the visual detection of 3D deformation.

A facile one-step microwave approach was employed to synthesize silver nanoparticle (AgNP) conductive ink. The conductive ink contained multi-sized silver nanoparticles. Different particle size distribution can be obtained by adding different amounts of the silver source. The relationship between the conductivity of the direct written pattern using the as-prepared silver conductive ink, the particle packing morphology and the particle size distribution standard deviation was investigated. Among all the samples, conductive ink with a silver weight percentage of 10% can have an optimal electrical resistance of 98 μΩ cm after post-hot/pressure treatment at 100°C and 20 MPa for 10 min. The as-prepared conductive ink is of potential application in printed electronics because the sintering condition of low temperatures is feasible for most kinds of flexible substrate materials.

Silver micro/nanomaterials have attracted a great deal of attention due to their superior physicochemical properties. The atomic migration driven by electromigration or stress-induced migration has been demonstrated to be a promising method for the fabrication of metallic micro-/nanomaterials because of the advantage of simple processing. However, how to realize the controllable fabrication and mass production is still the critical technical problem for the method to be used in large-scale industrial applications. In this paper, the multilayered samples consisted of copper foil substrate, Ti adhesive layer, Ag film, and TiN passivation layer and with arrays of artificial holes on the passivation layer were applied to prepare arrays of Ag micro-particles. For the purpose of controllable fabrication, stress-induced migration experiments combined with finite element simulation were applied to analyze the influence of the passivation layer thickness and the heating temperature on the atom migration and Ag particles growing behavior. And the relationship between size of the fabricated Ag particles and the processing parameters of stress-induced migration experiments were also investigated. As a result, a proper structure size of the multilayered samples and heating temperature were recommended, which can be used for the Ag micro-particles controllable fabrication and mass production.

In this work, we present a simple technique to prevent electromigration damage in printed Ag thin wires. The Ag thin wire can be protected by a silicone rubber layer during current supply. A comparison between protected Ag wires and unprotected Ag wires in the electromigration testing was made. Under same experimental conditions, electromigration induced damage including voids, hillocks and open circuit can be avoided by using the protection layer. It was found that the silicone rubber layer caused a resistance to prevent electromigration damage, the resistance increased with increasing the thickness of protection layer. This technique can provide great potential applications for improving reliability in electronic devices on both rigid and flexible substrate.

Current-induced changes of surface morphology in printed Ag thin wires were investigated by current stressing tests and numerical simulation. The samples were printed Ag thin wires on a flexible substrate with input and output pads. Different experimentalresults were obtainedthroughchangingthe current density after current supply and the mechanism of those phenomena were investigated by numerical simulations based on the method of atomic flux divergence. Good agreement between the simulations and experimental results was reached. It was found that electromigration was the main factor that caused the change of the surface morphology. The contribution of thermal migration can be ignored, and the Joule heating lead by the supplied current had a very significant accelerating effect on electromigration. Guidelines for effectively changing the Ag thin wire surface through providing predetermined current density was proposed, which were expected to be useful for improving the electrical reliability and lifetime of printed Ag thin wires in flexible electronic devices.

Recently, organic thermoelectric (TE) materials have attracted increasing attention in green energy conversion. However, researches on polymer nanostructured TE materials are still scarce, especially for the 1 D nanostructured polymer materials. In this work, 1D poly(3,4-ethylenedioxythiophene) (PEDOT) nanofiber was synthesized by a self-assembled micellar soft-template approach using anionic surfactant sodium dodecyl sulfate (SDS). Then, a flexible and free-standing PEDOT nanofiber film was prepared through a simple vacuum-assisted filtration method. FE-SEM and TEM characteristics real 1D configuration for all the PEDOT nanostructures. Through adjusting the molar ratio of SDS, oxidizing agent FeCl3 and EDOT monomer (nSDS: nFeCl3: nEDOT), nanofiber with different diameter (10–200 nm) and microtopography can be obtained. Electrical conductivity and Seebeck coefficient measurement indicates that the TE properties of PEDOT can be effectively tuned by adjusting its nanostructure, and a variation range as high as three orders of magnitude for the power factors (10-2–101 μW/mK2) can be realized. Due to a more ordered structure caused by the edge-on packing mode of PEDOT chain, the sample prepared with nSDS: nFeCl3: nEDOT = 30:15:7 shows the highest power factor of 7.2 μW/mK2. This value can be further enhanced to 14.4 μW/mK2 by constructing PEDOT nanofiber/SWCNTs composite.

A multilayered metallic structure, consisting of Cu foil and subsequently deposited Ag thin film covered with a passivation layer, was proposed to fabricate Ag micro/nanoparticles by stress migration. With employing a ductile Pt or brittle TiN thin film as passivation, Ag micro/nanoparticles were successfully fabricated by annealing the corresponding multilayered structure. The relationship between characteristics (average diameter, number and volume) of the formed Ag micro/nanoparticles and the annealing temperature was discussed. On this basis, the growth mechanism was developed, which indicates that the dimension of Ag particles was mainly dominated by the different pathways for the migration of diffused Ag atoms in the passivation layers of Pt and TiN and the annealing temperature.

Ag thin wires in the 1–2 µm diameter range with lengths of up to ~680 µm were fabricated in a metallic multilayer sample using stress migration. The sample, which was heated under atmospheric conditions, was a thin Ag film deposited on a Cu foil with an adhesion film of Ti and covered with a TiN passivation film. A compressive stress gradient, formed in the Ag film during the heating treatment, was the driving force for atomic diffusion. A tensile stress was produced in the TiN film, and brittle fracture occurred to cause cracks after the tensile stress exceeded the fracture strength of TiN. The cracks provided pathways for atomic discharge to generate long Ag thin wires. It was noted that a thick TiN passivation film was indispensable for wire formation. The long Ag thin wires may provide great potential applications as component materials in flexible transparent electrodes, integrated circuits and electromagnetic systems.

Non particle nano Ag conductive ink is a promising material for the patterning of flexible circuits by using the electrohydrodynamic micro printing technology. The pulse voltage control mold has been mainly used in the on demand droplet control in the patterning process. In this paper, the effect of pulse voltage amplitude on cone jetting behavior of this ink in one pulse period has been investigated by using the sequential images technology. Results indicated that under the same base direct current voltage applied on the nozzle, the pulse voltage applied on the substrate induced pulsant cone jetting rather than stable cone jetting in a pulse period if the value is under a critical value. When the voltage amplitude above this critical value was used, the stable cone jetting was obtained for each ejection. The increasing voltage amplitude resulted in the shortening of jetting starting time and also the ending time, and the jetting duration was decreased with the increasing of pulse voltage amplitude. There...

A comparison between stress migration (SM) and electromigration (EM) in the fabrication of thin Al wires was made. The samples used in each case had the same structure and were manufactured by depositing a thin Al film on a SiO2 layer, a native oxide layer covering the Al film. Al microwires were formed by SM by wide-area atomic migration, meanwhile, nanowires were formed by EM through local accumulation of atoms. It was found that the mechanisms of wire formation were same in both SM and EM tests except the ability of accumulating atoms. Al micro/nanowires with controlled geometry can be fabricated by SM or EM.

To understand morphological evolution and migration behavior caused by stress migration and thermal fatigue of silver thin films on flexible substrates, bending tests were conducted with different bending angles for two types of thermal tests. Furthermore, the effect of stress migration and thermal fatigue on the electrical conductivity of the silver thin films was discussed. The experimental samples were silver thin films printed on flexible paper for these tests. In an ultra-low cycle thermal test, the electrical conductivity of a silver film decreased with increasing bending angle because of the occurrence of voids caused by stress migration. Meanwhile, a high-cycle thermal test caused cracks to form and caused further deterioration of the electrical conductivity owing to a combination of stress migration and thermal fatigue.

The effect of purity on the fabrication of Al micro/thin-materials (MTMs) by utilizing electromigration (EM) has been investigated. The samples that were used to fabricate the Al MTMs were passivated polycrystalline Al lines incorporating a slit and small holes at the anode end of each sample. Al materials of different purity, 99% (2 N) and 99.99% (4 N), were used, and it was found that the atomic flux of the 2 N sample was significantly larger than that of the 4 N sample, leading to the enhanced fabrication of Al MTMs due to EM under the same experimental conditions, which turned out to be related to a decrease in the activation energy for grain boundary diffusion.

The fabrication of electromigration induced micro-belts in passivated aluminum films was investigated. The experimental sample was a passivated polycrystalline Al line with a slit and a rectangular hole at the anode end. The micro-belts could be formed at predetermined positions, with their length dependent on the current stress time, and their widths and thicknesses controlled by the size of the hole. It was found that the growth of the micro-belt is affected by the purity of Al, the current density and the current stress time. The experimental results are explained in the discussion.

We present a mechanism for controlling the accumulation and discharge of Al atoms using electromigration, by which long thin Al wires of lengths up to 336 µm and diameters ranging from 0.8 to 4 µm were fabricated. The experimental samples were Al lines formed on a TiN layer and covered with a SiO2 passivation layer. A slit in the Al film and a hole through the oxide or through the oxide and the Al film at the anode end of the line were used to control the accumulation and discharge processes. It was found that the position of the bottom of the hole, which was either at the SiO2/Al or Al/TiN interface, significantly affected these processes. A hole introduced down to the Al/TiN interface prevented cracks from forming in the line by relieving the compressive stress caused by accumulating atoms, and helped to extend the lifetime of the line. Guidelines for effectively controlling the accumulation and discharge of Al atoms were drawn, and based on these guidelines, other Al microstructures requiring the accumulation of a large number of atoms were fabricated after several tens of minutes of current supply.