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Adaptability to unstructured objects and the avoidance of target damage are critical challenges for flexible grippers in fruit-picking robots. Most existing flexible grippers have many problems in terms of control complexity, stability and cost. This paper proposes a flexible finger design method that considers contact behavior. The new approach incorporates topological design of contact targets and introduces contact stress constraints to directly obtain a flexible finger structure with low contact stress and good adaptability. The study explores the effects of design parameters, including virtual spring stiffness, volume fraction, design domain size, and discretization, on the outcomes of the flexible finger topology optimization. Two flexible finger structures were selected for comparative analysis. The experimental results verified the effectiveness of the design method and the maximum contact stress was reduced by about 70%. An adaptive two-finger gripper was developed. This design allows the gripper to achieve damage-free grasping without additional sensors and control systems. The adaptive and contact performances of the grippers with different driving modes were analyzed. Practical grasping tests were also performed, including evaluation of adaptive performance, stability, and maximum grasping weight. The results indicate that gripper 2 with flexible finger 2 excelled in contact stress and adaptive wrapping, making it well-suited for grasping unstructured and fragile objects. This paper provides valuable insights for the design and application of flexible grippers for picking robots, offering a promising solution to enhance adaptability while minimizing target damage. [ABSTRACT FROM AUTHOR]

In this Letter, we present a multistage smart radiator with a gradient emittance that gradually increases with increasing temperature in the spectral range of 2.5–15 μm. Such smart radiator is a relatively simple multilayered structure composed of three phase change materials (PCMs): VO2, GST, and IST. The smart radiator achieves multistage manipulation of emittance through phase transitions of PCMs, with the largest emittance tunability of ∼0.85. The underlying mechanism involves manipulating the Fabry–Pérot resonance and antireflection. Additionally, the emittance is found to be relatively insensitive to polarization and incident angles. The proposed multistage smart radiator exposes excellent potential for exploitation in thermal management and energy conservation. [ABSTRACT FROM AUTHOR]

BACKGROUND: The effective deposition of pesticide droplets on a target leaf surface is critical for decreasing pesticide application rates. The wettability between the target leaf surface and the pesticide spray liquid should be investigated in depth, with the aim of enhancing the adhesion of pesticide solutions. The wetting and deposition behavior of pesticides on target leaves depends on the properties of the liquid and the physical and chemical properties of the leaves. The physical and chemical properties of leaves vary with growth stage. This study aims to investigate the wetting behavior of banana leaf surfaces at different stages. RESULTS: The microstructures and chemical compositions of banana leaf surfaces at different stages were studied using modern methods. The surface structure of banana leaves exhibited a wide variety of characteristics at different growth stages, and the chemical composition changed marginally. The surface free energy (SFE) and polar and non‐polar components of banana leaves at different growth stages were measured by examining the contact angles (CA) of different test solutions on the surface of banana leaves. Previous research has suggested that changes in the CA and SFE correlate with changes in leaf surface wettability. In general, the new upper leaves of banana trees are composed of polar components and exhibit hydrophobicity. Non‐polar components become dominant as the leaf grows. The back surface of banana leaves was non‐polar at all growth stages, with a trend that was opposite to that of the front surface. The critical surface tension of the banana leaf surface at different growth stages ranged from 7.83 to 24.22 mN m−1, thus falling into the category of a low‐energy surface. CONCLUSION: The surface roughness and chemical characteristics of banana leaves affected the wettability of the leaf surface. Differences in the free energy and the polar and non‐polar components of the leaf surface at were seen at different growth stages. This study provides a favorable reference for the rational control of pesticide spraying parameters and the enhancement of wetting and adhesion of the solution on banana leaf surfaces. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Phase-Change Materials (PCMs) are widely applied in dynamic optical modulation due to the dramatic changes in their complex refractive index caused by temperature variation. As the functionality varies, the application of a single PCM cannot meet the compact, efficient and broadband needs of optical modulators. In this work, we combine vanadium dioxide (VO2) and a chalcogenide (Ge2Sb2Te5 (GST) or In3SbTe2 (IST)) to obtain a VO2–GST/IST multiple-stack film that is optimized by a genetic algorithm. This film has a wide spectrum and high modulation properties with three self-switchable modes varied by temperature, including transmission, absorption and reflection. The optimal results are an average normal transmittance, absorbance, and reflectance of 0.76, 0.91, 0.86 in 3–5 μm and 0.72, 0.90, 0.90 in 8–14 μm under different temperature ranges. The film enhances the transmission and absorption properties due to the formation of anti-reflective coating and Fabry–Perot resonance. Compared with GST, the film maintains high reflectance due to the metal-like interface reflection of crystalline IST, which exhibits metallic properties. For different polarization states, the film demonstrates great directional insensitivity when the incidence angles vary from 0° to 60°. The designed self-adaptive multistage infrared radiative thermo-optic modulator has promising implications for optical fuse, fiber-optic communication and energy storage fields. [ABSTRACT FROM AUTHOR]

The rapid development of the Internet of Things increases the demand for wearable devices. Compared with traditional chemical batteries, flexible thermoelectric technology contributes a solution for solving the power supply of wearable electronics. Here, we prepared n-type Bi2Te3 and p-type Bi0.5Sb1.5Te3 flexible thermoelectric films by the magnetron sputtering method, where the thermoelectric performance and their microstructures are systematically studied. The carrier concentration and mobility are optimized by adjusting the deposition temperature, eventually improving the thermoelectric performance and achieving the room-temperature power factors of 3.2 and 6.1 μW cm−1 K−2 for Bi2Te3 and Bi0.5Sb1.5Te3 films, respectively. Furthermore, after being bent 900 times with a radius of 5 mm, the resistance of these films barely increases, demonstrating the great potential for applications in wearable electronics. In order to further evaluate the practicability, these films are used to design a flexible thermoelectric generator, in which output performance improves with the increase in the temperature difference. The power density is up to ∼218.8 μW cm−2 at temperature differences of ∼41 K. [ABSTRACT FROM AUTHOR]

The achievement of low-resistance connection in REB2C3O7-z (REBCO, RE = Y, Gd) coated conductors (CCs) has become one of the strategic factors for magnet applications. In this letter, we fabricated low-resistivity (Rsj = 4.9 nΩ·cm2) Ag-diffusion joints of REBCO CC by improving the interface connection of the Ag stabilizer. The effective contact area at the interface between two Ag stabilizers can be increased by polishing the surface of the Ag stabilizers, which can reduce joint resistance (Rj). Compared with a traditional diffusion temperature (400 °C), diffusion bonding of the Ag stabilizers at higher temperatures (800 or 850 °C, typical connection temperatures for superconducting joint) can promote interface connection between two Ag stabilizers. The oxygen content in REBCO will be reduced due to diffusion bonding at higher temperatures. Therefore, we etched some microchannels that serve as the fast oxygen diffusion paths on the surface of the Ag stabilizers to help restore the oxygen content, thereby recovering critical current (Ic) and reducing Rj. The connection mechanism of the interface between two Ag stabilizers was investigated through the cross-sectional analysis and delamination of the joint part. In addition, the REBCO layer can be completely peeled off and almost retain the original Ic by diffusion bonding of the Ag stabilizers at higher temperatures. This fabrication technique is a unique practicable solution to reduce the Rj for the CC with thin Ag stabilizers and improve the peeling quality of the REBCO layer for efficiently fabricating the superconducting joint. [ABSTRACT FROM AUTHOR]

The YBa2Cu3O7-x (YBCO) coated conductor (CC) is one of the most promising superconducting materials because of their high critical current (Ic) and low dependency of the Ic on the external magnetic field. For superconducting applications, a large number of joints are required to join relatively short YBCO CC tapes. In this paper, we study the electromechanical behavior of lap-jointed YBCO CC tapes fabricated by etching Cu stabilizer at its service temperatures (77 K) under self-field. The effects of etching Cu stabilizer on Ic and joint resistance (Rj) of YBCO CC tapes were discussed. The Rj was reduced and the Ic values of the joints are consistent with the parent CCs tape by etching the Cu stabilizer. Preferable electrical properties under applying axial tension are achieved and proved by the axial tension tests and finite element simulations. This fabrication technique is a unique practicable solution to reduce joint resistance for YBCO CC tapes with thicker metal stabilizing layers and improving electromechanical performance in second generation high temperature superconductor (2G HTS) devices. [ABSTRACT FROM AUTHOR]

Currently, banana harvest still relies on manual operation with high labor intensity. With an aging global population, it is important to develop a machine to replace the manual harvesting of bananas to increase sustainability. In the area of robotic fruit harvest, most of the existing studies have used one single manipulator to grip the fruit. However, unlike other fruits, the weight of a banana bunch (25–40 kg) would be too heavy for one single manipulator. To solve this problem, this paper proposes a flexible supporting device, which was introduced to cooperate with the manipulator to complete banana harvest. The supporting device was designed to hold the bottom and the weight of the banana bunch. It included two parts: the flexible contact part and the height difference self-adjusting part. The shape adaptability, size adaptability, and height difference adaptability of the proposed supporting device were studied in this paper. The process of supporting bananas was also simulated and analyzed. The stiffness and stress properties of the device during this process were studied. The results showed that the flexible supporting device had a good adaptive performance for supporting different shapes and sizes of objects. During the supporting process, the device worked stably and reliably and caused small stress on the banana skin. Finally, a prototype of the supporting device was used to further verify the performance of the device. This research can promote the mechanization and automation progress of the harvesting of such a complex crop as bananas. [ABSTRACT FROM AUTHOR]

• By etching Cu stabilizer, the joint resistance (R j) can be reduced by removing the cupric oxide of the surface layer and shortening the current path between the two YBCO layers. • Preferable electrical properties under applying bending deformation are achieved and proved by the bending tests and finite element simulations. The evidently enhanced I c retention is found by bending tests. The stress and strain of the YBCO layer can be reduced due to employ thinner etching joints. • The employment of spot welding can further enhance the strength at the edges of the joint and thereby alleviate the I c degradation. The YBa 2 Cu 3 O 7 − x coated conductor (YBCO CC) is one of the most promising superconducting materials for magnet applications because of its high critical current (I c) and low dependency of the I c on the external magnetic field. For magnet applications, plenty of joints are required to meet the connection of relatively short YBCO CC tapes. The bending properties of the joints inevitably become one of the critical factors that determine the performance of the superconducting magnet. In this paper, we fabricated the joints of YBCO CC tapes by etching Cu stabilizer and studied their bending properties under various bending diameter at 77 K and self-field. Compared with the soldering joint, lower joint resistance (R j) and preferable electrical properties under applying various bending deformation were achieved and proved by the bending strain tests and finite element simulations. This fabrication technique is a unique practicable solution to reduce the R j and improve the bending properties for the joints of YBCO CC tapes with thicker metal stabilizing layers in second generation high temperature superconductor (2G HTS) applications. [ABSTRACT FROM AUTHOR]