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Abstract Soft robots have the advantage of adaptability and flexibility in various scenarios and tasks due to their inherent flexibility and mouldability, which makes them highly promising for real‐world applications. The development of electronic skin (E‐skin) perception systems is crucial for the advancement of soft robots. However, achieving both exteroceptive and proprioceptive capabilities in E‐skins, particularly in terms of decoupling and classifying sensing signals, remains a challenge. This study presents an E‐skin with mixed electronic and ionic conductivity that can simultaneously achieve exteroceptive and proprioceptive, based on the resistance response of conductive hydrogels. It is integrated with soft robots to enable state perception, with the sensed signals further decoded using the machine learning model of decision trees and random forest algorithms. The results demonstrate that the newly developed hydrogel sensing system can accurately predict attitude changes in soft robots when subjected to varying degrees of pressing, hot pressing, bending, twisting, and stretching. These findings that multifunctional hydrogels combine with machine learning to decode signals may serve as a basis for improving the sensing capabilities of intelligent soft robots in future advancements.

High piezoelectric composite films composed of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and ferromagnetic cobalt ferrite (CoFe2O4) (0.00 ​wt% to 0.2 ​wt%) are prepared by a solution casting method accompanied by uniaxial stretching and high electric field poling. The decisive effect of the poling electric field on the power generating capability was confirmed by the experiments. For pure PVDF-HFP films, when the maximum electric field Emax is 120 ​MV/m, the calibrated open circuit voltage reaches 2.93 ​V, which is much higher than those poled at lower electric fields (70 ​MV/m: 1.41 ​V; 90 ​MV/m: 2.11 ​V). Furthermore, the addition of CoFe2O4 also influences the piezoelectricity dramatically. In the samples containing 0.15 ​wt% CoFe2O4, the calibrated open circuit voltage increases to the maximum value of 3.57 ​V. Meanwhile, the relative fraction of the β-phase and the crystallinity degree are 99% and 48%, respectively. The effects of CoFe2O4 nanoparticles on initial crystallization, uniaxial stretching and high electric field poling are investigated by XRD, FTIR and DSC.

Abstract Ignition advance angle is one of the important factors affecting the performance of the engine, when it occurs abnormally will make the engine power and economy worse, and even cause serious damage to the engine. Therefore, it is very necessary to recognize the abnormal ignition advance angle of the engine. However, the engine system is closed and has a complex structure, which makes traditional diagnostic methods difficult. This paper proposes an intelligent identification method based on acoustic emission (AE) signals, which collects the AE signals from the engine surface and divides their spectra into equal parts, and selects the frequency bands with high contribution to the classification based on the minimum distance method to construct feature maps, which is used as the input to the convolutional neural network (CNN). The extracted frequency band features of this method can better characterize the AE signals, and the constructed feature maps make the fault information more obvious. Experiments show that the accuracy of this method for abnormal ignition advance angle under normal operating conditions of piston aero-engine is 100%, which is better than the traditional methods. In addition, the recognition accuracies under the other two operating conditions are 99.75% and 98.5%, respectively, indicating that the method has a certain universality.

As a representative flexible piezoelectric polymer, polyvinylidene fluoride (PVDF) and its copolymers have been widely used in energy harvesters and piezoelectric sensors. In this work, hybrid nanocomposite films were prepared by adding a small amount of carbon black (CB) and Ni nanoparticles to the poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrix using the solution casting method, followed by stretching and poling to increase the electroactive β-phase content. The results show that the hybrid fillers consisting of 0.3 wt% CB and 0.1 wt% Ni nanoparticles exhibit the best piezoelectric performance. The maximum output voltage of the PVDF-HFP/CB/Ni films reaches 3.5 V under 1 mm micro-vibration, which is 75% higher than that of pure PVDF-HFP films. Characterization results by X-ray diffraction analysis, Fourier-transform infrared spectrometry, and differential scanning calorimeter analysis show that the hybrid fillers are more effective in promoting the phase transformation from the α-phase to the β-phase in the matrix due to synergistic effect.

In recent years, PVDF(polyvinylidene fluoride) and its copolymers have attracted great attention in the development of energy-harvesting devices because of their unique properties such as good flexibility, environmental friendliness, high halogen and acid resistance, lightweight and good biocompatibility. Compared to the most commonly used PZT (lead zirconate titanate), the piezoelectricity of PVDF and its copolymer-based materials is relatively low. To further expand the applications of PVDF, there is an urgent need for efficient methods to prepare high piezoelectric polymers or composites. In this work, the crystal phases are introduced first. Then, the preparation methods of PVDF and its copolymer-based materials are summarized, which are mainly focused on four determining factors of piezoelectricity. The mechanisms of piezoelectric β-phase formation and α- to β-phase transformation are introduced. The influence parameters of each process and their interactions are discussed in detail. In the last section, the progress of the preparation methods is summarized. This work will provide useful information to researchers working on piezoelectric composites.

The composites with multiple types of nano-carbon fillers have better electrical conductivity and piezoresistive properties as compared with composites with a single type of nano-carbon fillers. As previously reported, the nano-carbon fillers with various aspect ratios, such as carbon nanotube (CNT) and carbon black (CB), have synergistic enhanced effects on the piezoresistive performance of composite sensors. However, most of the works that have been reported are experimental investigations. The efficient and usable numerical simulation investigation needs to be further developed. In this study, based on an integrated 3D statistical resistor network model, a numerical simulation model was created to calculate the piezoresistive behavior of the CNT/CB/ Polyvinylidene Fluoride (PVDF) composite. This model also takes into account the tunneling effect between nearby nano-fillers. It is found from numerical simulation results that the piezoresistive sensitivity of composite simulation cells can be influenced by the fraction of CNT and CB. In the case that the CNT content is 0.073 wt.%, the best force-electrical piezoresistive sensitivity can be achieved when the CB loading is up to 0.2 wt.%. To verify the validity of the simulation model, the previous experimental investigation results are also compared. The experimental results confirm the validity of the model. The investigation is valuable and can be utilized to design a strain sensor for this nano-composite with increased sensitivity.

Superhydrophobic composite strain sensors have attracted extensive attention due to their excellent waterproof, anti-icing, flexible and conductive properties, but there are still challenges to prepare it with broad sensing range, superior sensitivity, stable superhydrophobicity, and excellent long-term stability. In this study, we developed a multifunctional superhydrophobic silicone rubber (SR)/multi-walled carbon nanotubes (MWCNTs)/laser-induced graphene (LIG)/SR composite strain sensor using laser direct writing. A highly stable MWCNTs/LIG crosslinked conductive network layer, high-performance superhydrophobic layer, and stretchable SR layer were integrated to fabricate the sensor by tuning the laser parameters. The SR/MWCNTs/LIG/SR composite strain sensor possessed a high gauge factor of 667, large strain detection range of 0–230%, and a stable sensing response over 2500 cycles due to the MWCNTs/LIG crosslinked conductive network. Moreover, the SR/MWCNTs/LIG/SR composite strain sensor could effectively prevent icing owing to its anti-icing (36 min@-5 °C) and photothermal deicing (88 s@1 W/cm2@NIL) properties and hinder acid and alkaline (pH = 1–14) corrosion attributed to the laser-induced superhydrophobicity, thereby expanding its applications to acid, alkaline, and low-temperature environments. Consequently, the multifunctional superhydrophobic SR/MWCNTs/LIG/SR composite strain sensor is demonstrated to be suitable for human body motion detection in complex and severe environments.

Objectives: To analyze the correlation of prosthesis position selection during total hip replacement with clinical short and middle-term effects of Crowe III and Crowe IV hip dislocation. Methods: Clinical data of 28 cases of dysplasia and dislocation of the hip joint combined with severe osteoarthritis were retrospectively analyzed. During 2-year follow-up, patients were rechecked by imaging regularly to analyze the imaging changes of acetabulum prosthesis position and bone graft fusion. Harris hip score was used to assess the recovery of hip function. The correlation of prosthesis position and short and middle-term effects was analyzed. Results: The filling rate of medullary cavity of prosthesis was above 75%. The initial position was fixed and stable. The stability rate of femur-prosthesis interface reached 100%. Compared with pre-replacement, hip function was significantly improved at 6 months post surgery (p < 0.05). Conclusion: These results indicate that total hip replacement for Crowe III and Crowe IV hip dislocation can effectively reconstruct the acetabulum, recover hip function, and stabilize prosthesis. Total hip replacement is characterized by good filling rate, high stability of femoral prosthesis interface, and stable initial fixation. The clinical repair effect is strongly associated with the position of the prosthesis.

Objectives: To study the value of 3D printing of custom THA femoral prostheses with conventional femoral prostheses in total hip arthroplasty for severe hip deformity. Methods: Total hip arthroplasty was used in the treatment of 107 severe hip joint deformity cases from June 2018 to June 2019. Fifty-six patients received conventional hip replacement stems and 51 patients received a custom 3D printed hip replacement stem designed to address their proximal deformity and leg length discrepancy. The operation time, intraoperative blood loss, postoperative weight-bearing time, Harris score before and after the operation, complications after surgery and the main angle measurement of compared to their contralateral hip were evaluated to determine the short-term efficacy of 3D printed total hip replacement femoral prosthesis compared to the common total hip replacement femoral prosthesis. Results: A total of 107 patients were followed up for an average of 12 months. The use of 3D printing technology in the preoperative design and custom prosthesis fabrication was associated with shortened operation time, less intraoperative blood loss, quicker time to postoperative full weight-bearing, and improved the Harris score in 1 year after the operation compared to conventional total hip replacement stem (p.05). Conclusion: 3D printing technology created a virtual and realistic simulation, and personalized operation plan for patients with severe hip deformity, which was helpful for surgical treatment. The anatomical characteristics of patients with complex deformities were better addressed using the 3D printed femoral component and resulting in better patient outcomes and provided a new option for surgeons to manage these difficult cases.

In order to obtain high dielectric silicone rubber (SR)-based nanocomposites, graphene (Gr) was added by ultrasonication and mechanical mixing for the preparation of a microporous structure. It was discovered that the Gr content and the expansion rate had a great impact on the cellular structure. Based on the effects of the Gr content and the expansion rate on the dielectric property, hybrid materials were prepared and better properties appeared, as expected. For all samples, the dielectric constant increased with the Gr content until 3 wt% and then decreased. When the Gr content was 3 wt% and the expansion rate was 2, the dielectric constant reached 18.14 (1 kHz), which was 55% higher than that of the non-expansion sample (11.74) and several times that of the pure sample (3~6). Meanwhile, the dielectric loss was less than 0.01. This work proposed a method for producing high dielectric materials with important applications in the field of capacitors, sensors, and micro-resistors.

In this paper, a multifunctional slippery polydimethylsiloxane/carbon nanotube composite strain sensor (SPCCSS) is prepared using a facile template method. Benefitting from the slippery surface, the SPCCSS shows excellent liquid repellence properties, which can repel various liquids such as oil, cola, yogurt, hot water and some organic solvents. Meanwhile, the SPCCSS has a large strain sensing range (up to 100%), good sensitivity (GF = 3.3) and stable response with 500 cyclic stretches under 20% strain. Moreover, it is also demonstrated that the SPCCSS displays outstanding corrosion resistance (from pH = 1 to pH = 14) and anti-icing (8 min at −20 °C)/photothermal deicing (104 s with NIR power density of 1 W/cm2) properties, broadening its application in extreme acid, alkali and low-temperature conditions. Therefore, the multifunctional SPCCSS with the liquid repellence, anti-corrosion, and anti-icing/deicing properties has potential applications in wearable human motion monitoring tools under complex harsh environments.

A new wave energy flow (WEF) map concept was proposed in this work. Based on it, an improved technique incorporating the laser scanning method and Betti’s reciprocal theorem was developed to evaluate the shape and size of damage as well as to realize visualization of wave propagation. In this technique, a simple signal processing algorithm was proposed to construct the WEF map when waves propagate through an inspection region, and multiple lead zirconate titanate (PZT) sensors were employed to improve inspection reliability. Various damages in aluminum and carbon fiber reinforced plastic laminated plates were experimentally and numerically evaluated to validate this technique. The results show that it can effectively evaluate the shape and size of damage from wave field variations around the damage in the WEF map.

In recent years, nanocomposites based on various nano-scale carbon fillers, such as carbon nanotubes (CNTs), are increasingly being thought of as a realistic alternative to conventional smart materials, largely due to their superior electrical properties. Great interest has been generated in building highly sensitive strain sensors with these new nanocomposites. This article reviews the recent significant developments in the field of highly sensitive strain sensors made from CNT/polymer nanocomposites. We focus on the following two topics: electrical conductivity and piezoresistivity of CNT/polymer nanocomposites, and the relationship between them by considering the internal conductive network formed by CNTs, tunneling effect, aspect ratio and piezoresistivity of CNTs themselves, etc. Many recent experimental, theoretical and numerical studies in this field are described in detail to uncover the working mechanisms of this new type of strain sensors and to demonstrate some possible key factors for improving the sensor sensitivity.

Soft robots have the advantage of adaptability and flexibility in various scenarios and tasks due to their inherent flexibility and mouldability, which makes them highly promising for real‐world applications. The development of electronic skin (E‐skin) perception systems is crucial for the advancement of soft robots. However, achieving both exteroceptive and proprioceptive capabilities in E‐skins, particularly in terms of decoupling and classifying sensing signals, remains a challenge. This study presents an E‐skin with mixed electronic and ionic conductivity that can simultaneously achieve exteroceptive and proprioceptive, based on the resistance response of conductive hydrogels. It is integrated with soft robots to enable state perception, with the sensed signals further decoded using the machine learning model of decision trees and random forest algorithms. The results demonstrate that the newly developed hydrogel sensing system can accurately predict attitude changes in soft robots when subjected to varying degrees of pressing, hot pressing, bending, twisting, and stretching. These findings that multifunctional hydrogels combine with machine learning to decode signals may serve as a basis for improving the sensing capabilities of intelligent soft robots in future advancements. [ABSTRACT FROM AUTHOR]

Ephedra herb (EH), an important medicine prescribed in herbal formulas by Traditional Chinese Medicine practitioners, has been widely used in the treatment of viral pneumonia in China. However, the molecular basis of EH in viral pneumonia remains unclear. In this study, a ternary correlation multi‐symptom network strategy was established based on in vivo chemical profile identification and metabolomics to explore the molecular basis of EH against viral pneumonia. Results showed that 143 compounds of EH and 70 prototype components were identified in vivo. EH could reduce alveolar‐capillary barrier disruption in rats with viral pneumonia and significantly downregulate the expression of inflammatory factors and bronchoalveolar lavage fluid. Plasma metabolomics revealed that EH may be involved in the regulation of arachidonic acid, tryptophan, tyrosine, nicotinate, and nicotinamide metabolism. The multi‐symptom network showed that 12 compounds have an integral function in the treatment of viral pneumonia by intervening in many pathways related to viruses, immunity and inflammation, and lung injury. Further verification demonstrated that sinapic acid and frambinone can regulate the expression of related genes. It has been shown to be a promising representative of the pharmacological constituents of ephedra. [ABSTRACT FROM AUTHOR]