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The safety issue of robot becomes a key challenge in modern manufacturing industry, especially in the scenario of frequent human-robot collaboration. This paper presents a flexible ultrasonic proximity sensing skin which can be integrated on the surface of robot arm to ensure the safe human-robot collaboration. The sensing skin is composed of three pieces of aluminum nitride based piezoelectric micromachined ultrasonic transducers (PMUTs) arrays at the resonance frequency of 115 kHz and chip size of 4 mm × 4 mm × 0.5 mm. The three pieces of PMUTs arrays are evenly integrated on the flexible printed circuit board (FPCB) with a device size of 8.8 mm × 60 mm × 1.7 mm. The proximity sensing skin can detect obstacles within 300 mm and 60 degrees in front, and shows a large sensing coverage in comparison with capacitive/infrared devices. Besides, it is capable of sensing transparent materials like glass. Finally, since the small size and good scalability of micro-electro-mechanical system (MEMS), the PMUTs are easy to install onto robots and to integrate with other ultrasonic transducers in the future. This PMUTs based sensing skin will greatly enhance the sensing capability of robots and human safety during collaborative work.

This paper presents a novel flexible triaxial force sensor based on the capacitive pressure sensor array. The main structures of the sensor consist of the triangular pyramid microstructure electrode and the orthogonal triangular pyramid microstructure with the spacing of $20\ \mu\ \mathrm{m}$ , which makes the sensor have a large pressure detection range and high sensitivity at the same time. The triaxial force sensor based on the sensor array can measure the triaxial force in real time, and the ranges of normal force and tangential force are 0–3 N and 0–0.5 N, respectively. The proposed flexible triaxial force sensor is expected to have a good application prospect in the field of human-computer interaction.

This paper proposed a high-performance magnetic-coupled nonlinear electromagnetic generator (MNL-EMG). A high-permeability iron core is incorporated to the coil. The strong coupling between the iron core and the vibrating magnets lead to significantly improved output power and a broadened operating bandwidth. The magnetic force of the iron core to the permanent magnets and the magnetic flux density inside the iron core are simulated, and the dimension parameters of the MNL-EMG are optimized. Under acceleration of 1.5 g, the MNL-EMG can maintain high output performance in a wide frequency range of 17~30 Hz, which is 4.3 times wider than that of linear electromagnetic generator (EMG) without an iron core. The maximum output power of MNL-EMG reaches 174 mW under the optimal load of 35 Ω, which is higher than those of most vibration generators with frequency less than 30 Hz. The maximum 360 parallel-connected LEDs were successfully lit by the prototype. Moreover, the prototype has an excellent charging performance such that a 1.2 V, 900 mAh Ni-MH battery was charged from 0.95 V to 0.98 V in 240 s. Both the simulation and experiments verify that the proposed bistable EMG device based on magnetic coupling has advantages of wide operating bandwidth and high output power, which could be sufficient to power micro electronic devices.

This paper proposes a wide range 3 dimensional (3D) tactile sensor with variable sensitivity by using the robust bridge, array pyramid structure, and different Young's modulus and thickness of replaceable elastic layers on the assembled sensor's surface. In the structure of the sensor, the forces acting on the surface of the elastomer were transmitted to the bridges and silicon chip through the pyramids. Moreover, add one softer elastic layer on the surface of the PDMS cap, the hollow area will be compressed larger under the action of pressure since the hollow structure of the PDMS cap and different modulus between the elastic layer and PDMS cap. The sensitivities of this developed sensor increased three times compared to this sensor without an elastic layer in the measurement range of 100kPa (normal force).

Human-machine interface (HMI), as a medium for human to interact with machine, has gained more and more attention. Here, a glove-based HMI was proposed, integrated with ultra-stretchable strain sensors (USSs) based on functional liquid metal (FLM) and three-axis force sensors (TFSs) based on PDMS/MWCNT, to record bending angles and contact force of fingers, separately. The TFS endowed manipulator the ability of force perception so that it could better mimic the operations of skilled-workman. The USS and TFS have the advantages of high sensitivity, good linearity and low hysteresis, which enable the HMI with the capability of teleoperation and three-axis force perception.

Carbon-based CsPbI3 perovskite solar cells (CsPbI3 C-PSCs) without hole-transporting materials have been attracting much attention because of their high stability. However, the electron transport l...

Sensors based on triboelectric nanogenerators have been widely used for energy harvesting and sensing applications, however, the applications of multidimensional information perception and interactive control are insufficient. In this paper, we present an ultra-stretchable triboelectric strip sensor (TSS) using triboelectric mechanism for controlling the objects in three-dimensional space. This facile and low-cost TSS is mainly composed of a parallel structure including three symmetric sensor strips fixed on the base and a mobile stage connected with them. Based on the coupling effect of triboelectrification and electrostatic induction, the length changes of each strip with the same finger contacting point generate different signal output ratios from two terminal electrodes, functioning as the interactive interface for multi-dimensional sensing and controlling. Hence, the parallel sensor strips structure can realize the sensing and controlling in three degrees of freedom of linear motion and two degrees of freedom of rotational motion, and resultant sensing ranges are X, Y, Z, α and β (20 mm, 20 mm, 30 mm, 36°, and 36°). In terms of manipulation, this is simpler than the conventional controller with rigid structure and includes additional space dimensions. Furthermore, demonstration of the TSS as human-nanomachine terminal to control the nanomanipulator in scanning electron microscope (SEM) is successfully realized with the accuracy of 10 nm. The proposed TSS shows great potential for the applications in automated control, robotics control, and Internet of Things (IoT).

Summary: The CsPbI3 inorganic perovskite is a potential candidate for fabricating long-term operational photovoltaic devices owing to its intrinsic superb thermal stability. However, the carbon-based CsPbI3 perovskite solar cells (C-PSCs) without hole transport material (HTM) are currently disadvantaged by their relatively low power conversion efficiency resulting from the poor grain quality and mismatched energy band levels of the as-made CsPbI3 films. Herein we demonstrate that by doping Na into the CsPbI3 lattice, the grain quality is significantly improved with low defect density, and also, the energy band levels are better matched to the contact electrodes, affording a higher built-in potential. Consequently, the Voc of the C-PSCs is drastically increased from 0.77 to 0.92 V, and the efficiency from 8.6% to 10.7%, a record value for the CsPbI3 PSCs without HTM. Moreover, the non-encapsulated device showed virtually no performance degradation after 70 days of storage in air atmosphere. : Energy Sustainability; Materials Characterization; Energy Materials Subject Areas: Energy Sustainability, Materials Characterization, Energy Materials

Directly dispersing graphene into an electrolyte still remains a crucial difficulty in electrodepositing a graphene enhanced composite coating onto electrical contact materials. Herein, graphene was synthesized via electrochemical exfoliation in an N,N-dimethylformamide (DMF)/H2O solution containing (NH4)2SO4. The electrochemically exfoliated graphene nanosheets (GNs) were directly dispersed by sonication. In comparison with graphene synthesized from aqueous solution, the GNs electrochemically exfoliated in the DMF/H2O–(NH4)2SO4 solution exhibit a lower degree of oxidation. Cu/graphene composite coatings were subsequently electrodeposited onto Cu foils by adding Cu2+ into the as-fabricated graphene solution. The surface nanostructure of the Cu/graphene composite coatings was transformed from loose pine needles to a uniform and compact structure with an increase in the concentration of Cu2+, which indicated that the controllable synthesis of Cu/graphene composite coatings with different performances could be achieved in graphene dispersions after adding Cu2+. In order to synthesize graphene via electrochemical exfoliation and directly electrodeposit a Cu/graphene composite coating without adding CuSO4 or any other additive, an attempt was made to directly electrodeposit a Cu/graphene composite coating in CuSO4/DMF/H2O solution after electrochemical exfoliation.

More versatile and effective strategies are needed to prepare high-quality perovskites and their precursors for promoting the efficiency of perovskite solar cells (PSCs). Herein, the strategy of amine (CH3NH2, MA) gas treatment is successfully exploited to synthesize high-quality MAI precursors and MAPbI3 perovskites. During MA gas treatment, ethylammonium (EA) cations in EAI are completely substituted with the MA cations from MA gas to generate pure MAI. Furthermore, cation substitution induced by MA gas treatment is further extended to convert 1D EAPbI3 perovskites to 3D MAPbI3 perovskites. Compared with traditional perovskites, 1D-to-3D perovskites show a much smoother surface and lower defect density. Consequently, the performance and stability of carbon-based PSCs without hole transport materials are considerably enhanced. Therefore, amine gas treatment has been proved to be a versatile and promising strategy for preparing high-quality perovskites and their precursors.

CsPbBr3 with a large band gap (∼2.3 eV) is a promising material for fabricating perovskite solar cells (PSCs) with a high open-circuit voltage (Voc) and high stability. However, a suitable method is still lacking for depositing high-quality CsPbBr3 films. Herein, we develop a novel strategy to deposit high-quality CsPbBr3 films by employing a porous CsPb2Br5 film as an intermediate layer. Highly porous CsPb2Br5 films composed of lamellar crystals were obtained by immersing Pb–Br precursor layers in a low-concentration CsBr IPA solution. The low CsBr concentration helped to widen the processing window of CsPb2Br5, while the low-polarity IPA solvent served to keep the film structure stable during the reaction. High-quality CsPbBr3 films with full coverage, high purity and low defect density were obtained by further converting the CsPb2Br5 films in a high-concentration CsBr solution. After introducing the optimized CsPbBr3 film into a carbon-based PSC without a hole transporting material (C-PSC), a power conversion efficiency (PCE) of 6.1% and a Voc of 1.38 V were achieved. Moreover, the devices without encapsulation show almost no PCE decay after 200 days of storage in ambient air (25–85% relative humidity, 20–30 °C) and at 80 °C (10–20% relative humidity) for over 1080 h.

Thin protective films have been widely used for metal anticorrosion application. However, previous films either negatively influence the photoelectric property of metal surfaces or exhibit poor corrosion resistance. In this paper, an ultrathin adsorption film is built up through the effective use of linear/stereoscopic organosilicon. This kind of film is formed by the good 3-D shielding structure of a silicon resin and a linear oxosilane. Small molecule corrosion inhibitors fill the interstitial sites, leading to a compact composite structure. This film has little effect on the photoelectric property of the metal surface. Copper covered with this film achieves a contact angle of 118°and a protective efficiency of 99.34%, both of which are much higher than the previously reported for protective thin films. Moreover, such films could be adapted for various metal materials.

This paper reports a sensorized forcep with a minimized force sensing chip to facilitate Robotic-assisted Minimally Invasive Surgery (RMIS). A piezoresistive triaxial force sensor chip ( $2\ \text{mm}\times 2\ \text{mm}$ ) is developed and integrated in the grasping head of a continuum robot to provide additional tactile to the RMIS. Biocompatible hemisphere cap enhances the sensor's capability of triaxial force detection. A 3-dimensioanl (3D) force test is performed on the sensorized forcep. This simple strategy of configuration and sensing makes it possible in miniaturization of the forceps (outside diameter is less than 4 mm) for RMIS in the strictest operating space.

Traditional 3D printing technology is difficult to fabricate soft robots with complex structures and functions. However, embedded 3D printing technology has the ability to fabricate complex structures, including sensors, actuators, control system and power system integrated with soft robots. In this paper, based on the developed embedded direct inkjet 3D printing system, the magnetic slurry is printed inside Ecoflex materials to fabricate magnetically driven soft robots. Firstly, Comsol was used to study the rheological properties and viscosity properties of printing materials. Secondly, the optimal printing parameters are determined by the material ratio, mechanical stretching and 3D printing parameter experiments; Finally, the magnetic inchworm and gecko soft robots were printed by the determined optimal parameter, and bionic experiments were performed to verify the feasibility of integrated manufacturing of embedded 3D printing soft robots.

This paper proposed a hybridized energy harvester combining electromagnetic, piezoelectric, and triboelectric transduction mechanisms for ocean wave energy harvesting. Two energy harvesting mechanisms of wave shaking and heaving are contained in this device. The shaking energy harvesting mechanism (S-EHM) consists of a compound pendulum mechanism and a gear mechanism. Together with an electromagnetic generator (EMG) and a piezoelectric generator (PEG) are used to harvest the shaking energy of ocean waves. The heaving energy harvesting mechanism (H-EHM) consists of a sliding sub, mass slider and springs. Meanwhile, the triboelectric nanogenerator (TENG) is used to harvest the undulations energy of ocean waves. They all supply energy to the electrical appliances inside the marine buoy, which can extend its working life. The diameter of the harvester is 140 mm and the height is 185 mm. The tested maximum output voltages of the electromagnetic, piezoelectric and triboelectric parts are 12V, 18V, and 55 V, respectively. Moreover, the device can light up at least 90 LEDs and can power the temperature and humidity sensor to display the ambient temperature.

A Janus membrane/mesh is a type of functional membrane/mesh composed of opposing wetting properties formed into a single layer in order to achieve novel properties. Janus membranes/meshes have attracted increasing attention from materials scientists due to their promising applications in the fields of microfluid transportation, water–oil separation and cleaning energy applications. Herein, we report a simple method to fabricate a Janus mesh by combining opposite wettability functions into one copper mesh substrate. The superhydrophilicity is achieved by chemical etching and the superhydrophobicity is fabricated by hydrophobic SiO2 nanoparticle spraying. Due to its special composition and structure, the prepared mesh demonstrates distinct wetting properties on its two sides. Meanwhile, aqueous fluids can pass through the mesh from the hydrophobic side to the hydrophilic side spontaneously, whilst being blocked by the mesh when coming from the other direction. This unique property can realize unidirectional transportation of water fluids. The mechanism of the unique property based on Janus wettability is proposed and the stability of the prepared Janus mesh was also tested. The prepared Janus mesh can be used in the fields of microtidal energy, the chemical industry and in astronautics, demonstrating promising practical prospects.

We propose a glove based Human Machine Interface (HMI) designed for Virtual Reality (VR) and Augmented Reality (AR) applications. The proposed sensory glove uses facile designed triboelectric sensors to realize multi-dimensional motion recognition of gestures, and piezoelectric mechanical stimulators are also equipped for achieving the haptic feedback to user regarding the interactive events from virtual world. The developed HMI leverages machine learning technology to achieve real time object recognition, hence, we can manipulate virtual objects in VR/AR space by projecting sensory information from glove.

Carbon-based perovskite solar cells (PSCs) without hole transport material have attracted much attention due to their high stability. However, their power conversion efficiency (PCE) is still low because of the lack of suitable perovskite deposition methods. In this work, a facile solid-gas reaction method was explored to prepare high quality perovskite and the effects of precursor composition (PbI2, PbI2 + HI, HPbI3 and PbI2 + NH4I) on the CH3NH2 (MA) gas-induced perovskite were systematically investigated. The lack of H+/I− and/or HI suppressed the conversion of PbI2 precursor to MAPbI3, while rapid and complete conversion was achieved for (PbI2 + HI), HPbI3 and (PbI2 + NH4I) precursors. Compared with HPbI3 precursor, the presence of H2O molecules in (PbI2 + HI) precursor lowered the perovskite crystallinity, while the release of NH3 from (PbI2 + NH4I) precursor slower the interaction of MA molecules with MAPbI3 for achieving the highest quality MAPbI3 layer. The application of an anti-solvent treatment during precursor deposition further improved the quality of HPbI3 and (PbI2 + NH4I)-processed perovskite layers, which as a result, significantly promoted the photovoltaic performance of C-PSCs. Both devices exhibited considerably high stability, especially for the (PbI2 + NH4I)-processed C-PSCs, who did not show any PCE degradation after storage in air atmosphere at room temperature for 120 days.

Triboelectric nanogenerators and sensors have been widely adopted for diversified energy harvesting and sensing applications, but the demonstrations of 3D information sensing and controlling are very limited. In this paper, we present a novel self-powered virtual reality 3D-control sensor (VR-3D-CS) based on triboelectric mechanism for controlling the attitude (both the position and rotation) of object in 3D virtual space. This innovative, cost-effective, simple-designed sensor has a symmetric 3D structure with eight separated sensing electrodes and two touching spheres as the interactive interface with human fingers for 3D force information sensing and VR controlling. Based on the coupling effect of triboelectrification and electrostatic induction, the VR-3D-CS generates different electric output signals in response to different operation manner that can be used to control the attitude of objects in 3D virtual space. The symmetrical 3D configuration design of the sensor enables the detection of 3D force from both the normal direction and shear direction. By employing vector properties of force and signal analysis from the eight sensing electrodes, detection of six-axis directions in 3D space is achieved by triboelectric mechanism for the first time. The VR-3D-CS has been demonstrated to be able to detect normal force in the range of 0–18 N. It can resolve the shear force direction with step resolution of at least 15°. Besides, due to the positive output voltage and low internal impedance, the VR-3D-CS is readily compatible with commercial portable signal processing system for signal analysis and controlling. Demonstration of the VR-3D-CS as interactive interface for Augmented Reality (AR) control is successfully realized. The robust structure, stable output performance and self-powered sensing property enable the device as an ideal human machine interface towards AR interface, batteryless and energy saving applications.

Flexible electronic devices are developing rapidly, especially in medical applications. This paper reports an arrayed flexible piezoelectric micromachined ultrasonic transducer (FPMUT) with a sandwich structure for adjuvant treatment of bone injury. To make the device conformable and stretchable for attaching to the skin surface, the flexible substrate of polydimethylsiloxane (PDMS) was combined with the flexible metal line interconnection between the bulk lead zirconate titanate (PZT) arrays. Simulations and experiments were carried out to verify the resonant frequency and tensile property of the reported FPMUT device. The device had a resonant frequency of 321.15 KHz and a maximum sound pressure level (SPL) of 180.19 dB at the distance of 5 cm in water. In addition, detailed experiments were carried out to test its acoustic performance with different pork tissues, and the results indicated good ultrasound penetration. These findings confirm that the FPMUT shows unique advantages for adjuvant treatment of bone injury.

Inorganic cesium lead halide perovskites with superb thermal stability show promise to fabricate long-term operational photovoltaic devices. However, the cubic phase (α) of CsPbI3 with an appropriate band gap is unstable in air. We discover that highly stable α-CsPbI3 can be obtained in dry air (temperature: 20–30 °C; humidity: 10–20%) by replacing PbI2 with HPbI3 in a one-step deposition solution. Furthermore, the band gap of HPbI3-processed α-CsPbI3 is advantageously reduced from 1.72 to 1.68 eV due to the existence of tensile lattice strain. By employing such an α-CsPbI3 film in carbon-based perovskite solar cells (C-PSCs), a power conversion efficiency (PCE) of 9.5% is achieved, which is a record value for the α-CsPbI3 PSCs without hole transport material. Most importantly, over 90% of the initial PCE is retained for nonencapsulated devices after 3000 h of storage in dry air. Therefore, HPbI3-based one-step deposition presents a promising strategy to prepare high-performance and air-stable α-CsPbI3 PSCs.

Images with resolution beyond the diffraction limit (superresolution) were obtained by combining conventional microscopy with microscale microsphere, which provides a new possibility for real-time optical superresolution imaging. Here, we propose a method to manipulate the microsphere by attaching it to a probe with optical glue. The optical simulation has been performed to demonstrate the influence of probe on superresolution image. The probe was fixed on a translation stage which was regarded as a robotic manipulator with four degrees of freedom. The kinematic analysis of the robotic manipulator was studied for manipulation strategy of microsphere. The force analysis has been carried out to analyze the possibility of microsphere detach from probe. To improve imaging quality, the microsphere was immersed in liquid medium and the resolution of 130 nm (∼λ/4.5) was achieved. In addition, by scanning the microsphere at the speed of 5 μm/s over the sample surface and stitching the recorded images, the superresolution image of large continuous area was achieved. This work had important practical significance for manipulating microsphere and optical superresolution imaging.

During the process of preparing coal tar pitch and petroleum asphalt, it is technically difficult to remove adhered asphalt through heating, chemical solvents, mechanical methods, etc. In this pape...

Gradient wetting surfaces are getting increasing attention due to their wide application in multiple fields such as droplet movement and biosorption. However, the fabrication processes of full gradient wetting surfaces are still complex and costly. In present work, a facile and low-cost chemical immersion method was used to create a full gradient wetting surface. By controlling the displacement time in Ni2+ solution, the prepared surfaces perform hydrophilic to superhydrophilic. After being modified by stearic acid, the gradient hydrophilic surfaces convert into hydrophobic. The surface morphology, composition, and wetting behaviors of the as-prepared surfaces were systematically studied and discussed. The gradient wetting property could be attributed to the change in microroughness and surface energy. In addition, these surfaces also exhibited excellent self-cleaning and wax prevention properties. Furthermore, high stability and corrosion resistance were also found for these surfaces, which further highlight their promising practical applications in many fields.

α-CsPbI3 with the most suitable band gap for all-inorganic perovskite solar cell (PSC) application faces an issue of phase instability at low temperature in an air atmosphere. Herein, through stoichiometric investigation, α-CsPbI3 is successfully obtained with excess CsI at 110 °C in an air atmosphere. By doping α-CsPbI3 with Sb, phase stability is further enhanced and the film morphology is also improved. Carbon-based perovskite solar cells (C-PSCs) based on CsPb0.96Sb0.04I3 achieve a promising power conversion efficiency (PCE) of 5.18%, a record value for α-CsPbI3-based PSCs without hole transport materials. Significantly, the CsPb0.96Sb0.04I3 C-PSCs retain 93% of the initial PCE after 37 days of storage in an air atmosphere. Therefore, the synergistic effect of non-stoichiometry and Sb-doping presents a promising strategy to design all-inorganic lead halide PSCs with high performance and stability.

Alumina-silica particles contained zinc coatings on NdFeB are prepared by an in-situ electro-deposition method from alumina-silica sols contained plating bath. Alumina-silica sols with varied Si:Al ratio are prepared through the two step hydrolysis and condensation of aluminium isopropoxide (AIP) and tetraethyl orthosilicate(TEOS) with acid catalyst. As negative potential applied to NdFeB substrates promotes the deposition of zinc, it also causes the increase of hydroxyl ions concentration, which promotes the particle condensation and gel of alumina-silica sols. The effect of alumina-silica sols on the surface morphology, composition and performance of the electro deposited zinc coatings are studied for NdFeB substrate. The results show that the adsorption and gel of alumina-silica particles are along with the electro-deposition of zinc coating. As the Si:Al ratio increases in added sols, there are more alumina particles get embedded during electro-deposition, which affect the surface morphology and uniformity of zinc coating. Electrochemical and mechanical tests demonstrate that the embedded alumina-silica particles in zinc coatings may serve as inhibitors and help to improve the corrosion resistance and mechanical performance of the zinc coatings on NdFeB magnets.

Due to the extensive application of tin coatings, the electrodeposition mechanism, corrosion resistance and anti-discoloration performance have attracted attention in the past decades. In this paper, tin coatings containing sol particles were successfully prepared using the stable tin (IV) sols as the plating bath, based on the water-ethanol electrolytes. The particle size of the tin sols was largely in the range between 4 and 10 nm. When the sol contained 0.475 mol L − 1 SnCl 4 ·5H 2 O (Sol 2), the sol particles were uniformly deposited on tin coatings. The concentration of tin sol had a significant effect on the surface microstructure and preferred orientation of the electrodeposited tin coatings. The differences in nucleation process of the electrodeposition between tin sols and the aqueous acidic sulfate plating bath (sulfate bath) were revealed by electrochemical analysis. Compared with tin coatings deposited from sulfate bath, tin coatings deposited from Sol 2 had enhanced corrosion resistance and anti-discoloration performance.

Directly dispersing graphene in aqueous solutions, without chemical treatment or adding surfactants, remains an obstacle for plating metal-graphene composite coatings. In this study, graphene was prepared by electrochemical exfoliation of a graphite anode and directly dispersed in N, N-dimethylformamide (DMF)/H2O solutions containing CuSO4 (40, 80, and 120 g/L) without adding a surfactant. Cu/graphene composite coatings were electrodeposited in graphene dispersions. The Cu/graphene composite coating with the highest graphene content was obtained in a solution with 80 g/L CuSO4. The co-deposited graphene affected the preferred orientation and led to a different oxidation reaction rate between the Cu/graphene composite coatings. After thermal treatment, the Cu/graphene composite coating plated in the solution with 80 g/L CuSO4 exhibited the lowest oxidation degree. This indicates that co-deposited graphene reduces the oxidation degree of Cu/graphene composite coatings.

The application of CsPbI3 inorganic perovskite in carbon-based perovskite solar cells without hole transporter (C-PSCs) is expected to enhance device stability. However, due to the lower hole selectivity of carbon electrode than that of hole transporter, the efficiency of CsPbI3 C-PSCs is significantly suppressed. Herein, size mismatch-induced cation segregation in CsPbI3 is studied and employed to solve the problem. After treating CsPbI3 with CsX (X Br, Cl and F) ethanol solutions, the larger size mismatch between X- and I- ions would induce the more obvious cation segregation. The moderate size mismatch between I- and Cl- ions allows a partial substitution of I- ions with Cl- ions in CsPbI3 to form energy level gradient, and the CsCl residue on the surface tends to react with CsPbI3 to generate 2D Cs2PbI2Cl2 nanosheets, serving as an electron blocking layer. The synergistic effect of the energy level gradient and the electron blocking layer well improves hole selectivity at CsPbI3/carbon interface to reduce carrier recombination loss. As a result, the C-PSCs based on the CsCl-treated CsPbI3 achieve an efficiency of 15.23%, a record value for inorganic C-PSCs.

Soft robots have significant advantages in terms of flexibility and adaptability, leading to potential applications in the bionics field. Inspired by the caterpillars in nature, this work proposed a soft caterpillar robot (SCR) by integrating two types of ultra-stretchable bionic sensors on a dual air-chamber pneumatic network structure. In order to realize self-powered tactile sensing, four triboelectric nanogenerator tactile sensors (TTSs) based on functional liquid metal (FLM) with thorny-structured bionic whiskers are developed and attached on the SCR. Meanwhile, two ultra-stretchable resistive strain sensors (RSSs) by using FLM are covered as the bionic skin to sense self-body deformation of the SCR. The TTS has a fast response time of 0.03 s and a minimum perception of 0.05 kPa, which can be very sensitive to the unknown stimulus of various materials. The RSS with a relatively high sensitivity of 2.94 and small hysteresis of 1.42% possess the ultra-stretchable ability of 180% strain, which helps to adapt and adjust its own body bending and crawling. The biological perception capabilities of the SCR play a crucial role in mimicking bionic actions and response in an unknown environment, such as escaping from unexpected attacks as well as adaptive crawling through an unknown tunnel environment.

The inorganic CsPbI3 perovskite obtained from dimethylammonium iodide (DMAI)-related strategies have greatly promoted the development of CsPbI3 perovskite solar cells (PSCs). However, deeper understandings are urgently needed to further enhance device performance. Herein, the crystallization processes of DMAI-based strategy are systematically studied and some new understandings are proposed. During annealing, β-phase-like CsPbI3 is first formed and then gradually transits to γ-phase-like structure. DMA ions tend more to form DMAPbI3 in the system, implying the amount of alloyed DMA ions in CsPbI3 would be very limited. In addition, the pre-generated Cs4PbI6 plays an important role in stabilizing CsPbI3 perovskite phase at low temperature. These findings help us to finely manipulate film composition, and the quality of CsPbI3 film is substantially improved after simultaneously suppressing the formation of δ-CsPbI3, minimizing DMAPbI3 residual and generating PbI2 passivator. More promisingly, the carbon-based CsPbI3 PSCs without hole transporter achieve a record efficiency of 14.6%.

Tremendous effort has been devoted to develop CeO2/polymer nanocomposites due to their excellent ultraviolet radiation absorption properties. However, there still exists many challenges in the successful incorporation of CeO2 nanoparticles into the polymer matrix because the ease aggregation of CeO2 nanoparticles. Here, we addressed the above issue by anchoring CeO2 nanoparticles on functionalized SiO2 spheres before their introduction into polymeric matrix, in which monodispersed vinyl group coated SiO2 spheres were synthesized by co-condensing tetraethoxysilane and 3-methacryloxypropyltrimethoxysilane, followed by coating with small size CeO2 nanoparticles (CeO2@M-SiO2) through chemical precipitation. The polymer composite film prepared by importing CeO2@M-SiO2 into fluorinated polyacrylate through miniemulsion polymerization exhibited enhanced UV absorption capacity, accompanied with an obvious improvement in hydrophobicity due to the increase in the surface roughness and fluorine content. Furthermore, the formation mechanism of the nanocomposite film was proposed: a polymer layer would form around the nanoparticles after film formation. This fluorinated polyacrylate/CeO2@M-SiO2 composite film is anticipated to be practically applied as outdoor coatings.

Iron sulfide has been proved to be a promising material for counter electrode (CE) of QDSCs in our previous work. However, the fill factor is still much below expectation, owing to the poor catalytic activity. Herein, iron sulfide nanosheets are embedded into porous carbon. This structure exhibits good interfacial contact between iron sulfide and carbon. As a result, it improves the stability of the CE, promotes the interfacial electron transfer rate between iron sulfide and carbon, and increases active sites leading to superior catalytic activity. Consequently, the QDSC based on this optimal structure obtains a power conversion efficiency of 5.61% with higher FF (0.64) compared with those with Pt or other conventional sulfide based CEs. Besides, we developed a novel facile, reproducible and printable preparation process: compositing and chemical conversion (3C).

Photopolymer film has been widely used in optical devices. However, the low initiator efficiency limits its wider development. In this study, Methylene blue (MB)/N-methyldiethanolamine (MDEA) and MB/1,4-diazabicyclo [2.2.2]octane (DABCO) were first adopted as initiator system in photopolymer film and compared their initiator system efficiencies with the common initiator system MB/triethanolamine (TEA) by a self-established single-beam exposure setup. The MB/MDEA showed the highest performance, while the MB/DABCO was the poorest. The quantum yield, bleaching rate and saturated exposure of the MB/MDEA were 3.31 times, 2.62 times and 2.49 times, respectively, higher than those of the MB/TEA. This order of initiator system efficiencies (MB/MDEA > MB/TEA > MB/DABCO) is exactly consistent with the order of proton transfer efficiencies of the electron donors (MDEA > TEA > DABCO). Furthermore, high proton transfer efficiency and excellent migration of electron donors are helpful to improve initiator system efficiency via surface micromorphology analysis. Keywords: Photopolymer films, Initiator system efficiency, Electron donor

Alumina film is effective for improving the corrosion resistance and protecting the magnetic properties of NdFeB magnets, but the complicated preparation method limits its application. In this study, we prepare alumina sol (AS) film on NdFeB magnets with an electric chemistry method from modified alumina sol. And a hydrothermal treatment (HTT) improves the combination and protection ability of AS film on NdFeB. Microstructural investigation suggests that the uniform AS film can be prepared on NdFeB under optimized electric conditions and the hydrothermal treatment helps to repair defects on the AS film. With the formation of electro-deposited AS film, the corrosion current density value reduces more than an order of magnitude and the intergranular corrosion of NdFeB is obviously suppressed in corrosive environments. The thermal stability of NdFeB magnets is also improved by the AS film. The morphology, composition and phase transition of the AS film are systematically investigated. In addition, the underlying formation mechanisms for electro-deposited AS film have been analyzed by zeta potential measurement and cathode polarization measurement at the sol–metal interface. These results have important implications for the preparation of protection film to prevent magnetic loss on sintered NdFeB magnets.

Superhydrophobic coatings have attracted significant attention due to their wide potential applications. However, the practical applications of the present artificial superhydrophobic coatings are not only hindered by their environmentally hazardous components, containing fluorinated materials and pungent organic solvents, but also by their poor material stabilities. Herein, a robust water-repellent organic–inorganic composite coating based on an aqueous dispersion was developed using a non-fluorinated material system consisting of a waterborne silicone–acrylic copolymer (SAC) and silica sol. Uniquely, the as-prepared SAC containing acid functional groups was first ionized in an alkaline environment, followed by introduction of the silica precursor into the SAC to generate the silica sol in situ. The abovementioned non-fluorinated material system favors the application of the simple spray technique for the superhydrophobic coating (157.7°) deposition, which can be flexibly employed on various substrates. The resulting composite coating, in which strong micro- and nano-scale roughness structures are embedded in the layer matrix, can withstand at least 200 abrasion cycles while retaining its superhydrophobicity. Moreover, the composite coating also shows significantly high resistance to acid/base, organic solvent, UV photodegradation (UVA light illumination for 96 h) and high-temperature heating (400 °C for 80 h). Furthermore, this environmentally friendly coating can be easily applied in the self-cleaning (in either air or oil environments) and oil/water separation fields.

Superhydrophobic coatings have drawn much attention in recent years for their wide potential applications. However, a simple, cost-effective, and environmentally friendly approach is still lacked. Herein, a promising approach using nonhazardous chemicals was proposed, in which multiple hydrophobic functionalized silica nanoparticles (SiO2 NPs) were first prepared as core component, through the efficient reaction between amino group containing SiO2 NPs and the isocyanate containing hydrophobic surface modifiers synthesized by normal alcohols, followed by simply spraying onto various substrates for superhydrophobic functionalization. Furthermore, to further improve the mechanical durability, an organic–inorganic composite superhydrophobic coating was fabricated by incorporating cross-linking agent (polyisocyanate) into the mixture of hydrophobic-functionalized SiO2 NPs and hydroxyl acrylic resin. The hybrid coating with cross-linked network structures is very stable with excellent mechanical durability, sel...

The device instability has been an important issue for hybrid organic–inorganic halide perovskite solar cells (PSCs). This work intends to address this issue by exploiting inorganic perovskite (CsPbBr3) as light absorber, accompanied by replacing organic hole transport materials (HTM) and the metal electrode with a carbon electrode. All the fabrication processes (including those for CsPbBr3 and the carbon electrode) in the PSCs are conducted in ambient atmosphere. Through a systematical optimization on the fabrication processes of CsPbBr3 film, carbon-based PSCs (C-PSCs) obtained the highest power conversion efficiency (PCE) of about 5.0%, a relatively high value for inorganic perovskite-based PSCs. More importantly, after storage for 250 h at 80 °C, only 11.7% loss in PCE is observed for CsPbBr3 C-PSCs, significantly lower than that for popular CH3NH3PbI3 C-PSCs (59.0%) and other reported PSCs, which indicated a promising thermal stability of CsPbBr3 C-PSCs.

This paper proposes an impact-based micro piezoelectric energy harvesting system (PEHS) working with the frequency up-conversion mechanism. The PEHS consists of a high-frequency straight piezoelectric cantilever (SPC), a low-frequency S-shaped stainless-steel cantilever (SSC), and supporting frames. During the vibration, the frequency up-conversion behavior is realized through the impact between the bottom low-frequency cantilever and the top high-frequency cantilever. The SPC used in the system is fabricated using a new micro electromechanical system (MEMS) fabrication process for a piezoelectric thick film on silicon substrate. The output performances of the single SPC and the PEHS under different excitation accelerations are tested. In the experiment, the normalized power density of the PEHS is 0.216 &mu, W&middot, g&minus, 1&middot, Hz&minus, cm&minus, 3 at 0.3 g acceleration, which is 34 times higher than that of the SPC at the same acceleration level of 0.3 g. The PEHS can improve the output power under the low frequency and low acceleration scenario.

In this paper, an impact-based frequency up-converted piezoelectric energy harvesting system (PEHS) is proposed and fabricated using MEMS piezoelectric thick film technology. The PEHS mainly consists of a high-frequency piezoelectric cantilever (PC-H) with resonate frequency of 935 Hz and a low-frequency stainless-steel cantilever (SC-L) with resonate frequency of 23 Hz. Under the external low-frequency vibration excitation, the SC-L at the bottom impacts the PC-H during the movement, in this way the low-frequency external vibration is converted to high-frequency piezoelectric cantilever vibration. When the PC-H is triggered to vibrate at 935 Hz, the maximum voltage output is 74 mV at 1.0 g. Then incorporate the PC-H with SC-L and form the PEHS, at driving frequency of 20 Hz to 34 Hz, the maximum voltage output and 3dB bandwidth of the PEHS reach 1220 mV and 4.7 Hz, respectively. The maximum voltage output of the PEHS (1220 mV) is more than 16 times of that of the single PC-H (74 mV).

Because of the optical diffraction limit, standard optical microscopies are not suitable to directly observe the biological samples with the small size between 5 to 150 nm. It has been experimentally demonstrated that microspheres have the ability of super-resolution imaging. Here, we report a probe-combined microsphere which consists of a barium titanate microsphere with the diameter of $50 \sim 100 \mu m$ and a probe. The finite element method is performed by the COMSOL Multiphysics software to confirm that the probe has no influence on the microsphere imaging. When the probe-combined microsphere was installed on a three-dimensional precision translation stage, it can be moved to the desirable area to capture the tiny feature of rat liver slices and the appearance of cells. What’s more, the probe-combined microsphere can adsorb the cells on the back of the microsphere, and thus it can be used as a tool to pick up cells. Another probe can operate the cells and morphological changes of cells can be observed through the microsphere at the same time.

This paper reports an energy harvester based on pendulum to harvest energy from ultra-low frequency ocean waves. When the eccentric mass pendulum is subjected to an excitation wave, it generates a large angle of oscillation or even rotation. The kinetic energy collected by the device is transmitted to an electromagnetic power generation module through the gears. The motion behavior of the device under different wave amplitudes and frequencies are explored by using ADAMS software. The shape, size and material of the mass pendulum are optimized. In the simulation, the maximum open-circuit voltage of the device can reach to 15 V under the wave amplitude of 20 cm and frequency of 1 Hz. It has the maximum output power of 0.4 W with an external resistance of 100 Ω. When tested in a large experimental tank, the output of the device is also good. The maximum open-circuit voltage and power of the device can reach to 8 V and 0.16 W under the wave amplitude of 20 cm and period of 3 s. The volume of the device is 100 * 100 * 56 mm3.

Surface electromyography (sEMG) signals generated by the muscles of the lower jaw contain corresponding voice information when talking. However, it's very hard to collect sEMG signals from the jaw because of not only the weakness of the signals but also the sharp skin curvature of this area. This paper reports a super-flexible and high-sensitive epidermal sEMG electrode patch to measure sEMG signals of the jaw from which the voice information can be extracted for speech recognition. This epidermal sEMG patch can be effectively attached to the jaw and the interconnection wire in the form of double wave can stretch more than 100%. From the characteristic of envelopes of the signals, it shows good consistency when the tester speak the same word and obvious difference can be detected when the tester speak different words. Four-layer wavelet decomposition is used to reduce noise in sMEG records and the eigenvectors are extracted from wavelet coefficients to characterize each trial. The experimental result shows that the average accuracy of the three pronunciations is about 71.7%. The accuracy of “hello” reaches up to 91%. In the future his epidermal sEMG electrode patch has great potential for the application of silent speech recognition.

Residual stress can dramatically hamper the performance of piezoelectric micromachined ultrasound transducers (pMUTs), in particular the transmitting sensitivity. This paper reports a series of square pMUTs with enhanced transmitting sensitivity through V-shaped springs in different angles. The V-shaped springs can release the residual stress through self-deformation, which contributes to a flat vibrating membrane rather than a curved one. A flat vibrating membrane conduces to a large vibration amplitude. Consequently, the transmitting sensitivity of the pMUT with 150° V-shaped springs is measured as 50.9 nm/V, which is 203% higher than that of the pMUT without springs. The enhanced pMUTs have advantages in various applications of emission ultrasound.

Al2O3-contained zinc coatings with enhanced protective and mechanical performances were prepared on NdFeB magnets by in situ electro-deposition methods from the zinc plating baths containing alumina sol. The positively charged alumina sol particles migrate to the NdFeB cathode and then gel along with zinc on the cathode surface, which changes the electro-deposition process of zinc. As a result, the surface morphology and phase structure of the zinc coating is significantly changed. The incorporation of alumina particles achieves a denser zinc coating with a smaller grain size and the hardness is well improved. By increasing alumina sol concentration in the plating bath, the micro-hardness and wear resistance of the zinc coatings gradually increased. What's more, the alumina sol addition also improved the corrosion resistance of zinc coatings. When 20 wt. % alumina sol is added, the corrosion potential of the zinc coating is positively shifted for 168 mV and the corrosion current was more than one order magnitude lower than the blank one. Therefore, this approach shows great promise to obtain alumina-contained zinc coatings with enhanced anti-corrosion properties and mechanical properties.