Band 45, Heft 9

Magnetorheological (MR) materials are smart materials whose rheological properties change significantly under the influence of magnetic fields. These materials mainly include fluids, elastomers, and greases. The components of MR materials consist of magnetic particles, a non-magnetic carrier liquid or matrix, and additives. The unique MR effect of these materials makes them widely used in robotics and medical devices. Improving the properties of MR materials and utilizing their characteristics are of great significance for the design and application of modern electromechanical devices. Therefore, this paper presents the composition, characteristics, and working principles of MR materials, as well as the latest progress in their applications in robotics and medical devices. Firstly, the composition and fabrication process of MR materials are introduced. Then, devices based on MR materials, including actuators, clutches, dampers, pumps, grippers for robots and medical devices, and MR robots, are extensively reviewed. Finally, a discussion of future research directions and technological challenges is provided as the conclusion of this review. The aim is to provide useful information to facilitate the design of robots and medical devices. Graphical Abstract Among the advancements of soft-bodied robots or micro-robots, MR materials exhibit the ability to deform under external magnetic fields, making them highly suitable for fabricating robots. 29 , 66 , 67 Hua et al. 68 designed an MRF-filled soft crawling robot with magnetic actuation. The robot achieves anisotropic magnetic torque-driven crawling, avoiding magnetic interference when the field is off. It demonstrates potential for applications in confined spaces, offering a novel approach to soft robotics with improved control and fabrication efficiency. McDonald et al. 69 developed an MRF-based soft robot with integrated flow control components, where motion is regulated by magnetic field-induced changes in fluid viscosity and pressure drop. This design enables multi-degree-of-freedom actuation through a single inlet and outlet, reducing the complexity of fluidic connections. The robot achieves complex behaviors such as bending, gripping, and independent control of multiple actuators, improving both autonomy and scalability while preserving compliance and adaptability. Chen et al. 70 designed a solid-liquid state transformable MRF-Robot made from an MRF. The MRF-Robot can perform diverse tasks such as large deformation, splitting, merging, object manipulation, and gradient pulling, making it suitable for biomedical applications like drug delivery and thrombus clearance. Li et al. 71 developed an untethered MRF robot encapsulated within an elastic membrane. The robot can wrap and transport delicate objects like tomatoes without causing damage, and it can also navigate through complex mazes shaped like letters. These capabilities highlight its potential for handling soft objects and operating in confined spaces. Min et al. 72 reported a stiffness-tunable, soft adhesive robot inspired by the velvet worm, utilizing an MRE that rapidly changes stiffness under an external magnetic field. This robot achieves precise adhesion control with low preload, enabling delicate grasping of soft and wrinkled surfaces without damage. The robot can unscrew nuts, and assist in mouse tumor removal surgery, showing potential in biomedical engineering (Figure 2e Figure 1: Proportional classification of MR materials applications in robots and medical devices based on Refs. [28], [29], [30], [31], [32], [33], [34], [35 Copyright (2022), Institute of Electrical and Electronics Engineers. 28 Copyright (2023), American Chemical Society. 29 Copyright (2024), Institute of Electrical and Electronics Engineers. 30 Copyright (2020), Institute of Electrical and Electronics Engineers. 31 , 34 Copyright (2022), reprinted with permission from Tan et al. 32 Copyright (2023), Institute of Electrical and Electronics Engineers. 33 Copyright (2021), Institute of Electrical and Electronics Engineers. 35 Figure(s) reproduced with permissions from the institutions/holders mentioned. ).

Polyether ether ketone (PEEK) is a high-performance thermoplastic recognized for its outstanding mechanical characteristics, thermal stability, and chemical resistance. Besides, working with pure PEEK requires a lot of energy and can result in issues like thermal degradation if not handled carefully, which limits mechanical performance. The research intends to synthesize a high-performance PEEK hybrid nanocomposite layer series by PEEK/zirconia (ZrO 2 )/carbon fiber (CF)/PEEK with varied percentages of weight for ZrO 2 as 0–5 wt% adhered with the epoxy medium through hand layup associated with advanced hot compression mould technique. The response of nano ZrO 2 particles on microstructural and mechanical characteristics of PEEK/carbon fiber (CF)/PEEK hybrid composites is investigated. The PEEK/5 wt% ZrO 2 /CF-PEEK hybrid nanocomposite exploited superior mechanical performance rather than others, and microstructural transmission electron microscopy (TEM) analysis provides the clear fiber-filler matrix bonding, which favours better mechanical behaviour of the composite. Besides, the composite series of PEEK/5 wt% ZrO 2 /CF/PEEK is found to have optimum yield, tensile and flexural stress, and fracture toughness, with values 132.8 MPa, 182.5 MPa and 192.2 MPa, and 7.9 MPa 0.5 and proposed to automotive parts applications.

A comprehensive analysis of laser transmission welding (LTW) of acrylonitrile butadiene styrene (ABS), a widely used engineering plastic for structural applications, is presented in this research paper. The efficiency and reliability of LTW for ABS are examined by analyzing the complex interactions between process parameters and weld characteristics, as well as through the study of fracture surface characteristics and weld morphology. Systematic experimentation combined with response surface methodology is employed to develop precise mathematical models correlating process parameters with weld quality. Optimization strategies are explored to identify parameter configurations yielding desired weld quality. It is observed that higher laser power enhances weld strength by improving energy transfer, while careful balancing of scanning speeds prevents overheating, and increased stand-off distances improve both weld strength and width. Fracture surface analysis reveals significant fibril elongation and interlayer deformation, demonstrating the effectiveness of LTW in enhancing weld quality through improved interfacial bonding and material integration. The research provides key insights into LTW for ABS, emphasizing parameter interactions, weld quality, fracture characteristics, morphology, and optimal processing conditions for advanced engineering applications.

Sunflower stem pith-derived cellulose (SSPC) and nanocellulose (TOCN) were modified with polyethyleneimine (PEI) to enhance their adsorption of Cu 2+ and Cr 6+ . PEI modification significantly enhanced the adsorption capacity for Cu 2+ , increasing it by 5.2 times compared to pure cellulose. Meanwhile, TOCN-PEI exhibited superior adsorption performance for Cr 6+ , attributed to its higher PEI graft density compared to SSPC. The adsorption kinetics were best described by the pseudo-second-order model, while the Langmuir isotherm model provided the best fit for equilibrium data, indicating monolayer adsorption. Thermodynamic analysis revealed that the adsorption process was exothermic (ΔH 0 < 0) and less favorable at elevated temperatures. After five adsorption/desorption cycles, TOCN-PEI retained approximately 63.0 % of its initial adsorption efficiency, demonstrating reusability. Overall, TOCN-PEI is a promising adsorbent for Cu 2+ and Cr 6+ removal, offering exceptionally high Cu 2+ adsorption capacity (217.3 mg/g), effective Cr 6+ removal (196.7 mg/g), and good reusability.

The high-frequency, integrated, and miniaturized circuits increase the risks of electromagnetic interference and heat accumulation. However, it is difficult for the traditional circuit package substrate to realize both low dielectric and high thermal conductivity, resulting in high-quality signal transmission and fast heat dissipation cannot be achieved simultaneously. Here, for the first time, composite films (hBN/LCPs) with low dielectric constant in high-frequency and high thermal conductivity are prepared based on liquid crystal aromatic polyesters (LCPs) and hexagonal boron nitride (hBN). The highest thermal conductivity of hBN/LCPs film reaches 0.696 W m −1  K −1 , which is 3.3 times higher than that of the pristine LCPs. In the simulation of wafer heat dissipation, hBN/LCPs film shows a maximum surface temperature decrease of over 20 °C compared to the pristine LCPs, showing the fast heat transfer ability. The dielectric constants and dielectric losses of hBN/LCPs films keep the low values in the range of 0.4–1 GHz, being less than 3.4 and 0.007, respectively, meeting the requirements of 5G communication devices. Meanwhile, the hBN/LCPs films show good mechanical strength and heat resistance. Therefore, a low-cost and facile method is developed to prepare composite films with low dielectric and high thermal conductivity for 5G circuit package substrates.

Molding complex hollow products with intricate contours via plastic injection molding remains a major challenge due to mold design limitations. For example, components such as plastic intake manifolds are typically molded in separate segments and subsequently assembled. Traditional sand or salt cores used in metal casting are unsuitable for injection molding because molten plastics are thousands to millions of times more viscous than molten metals. As a result, these cores are prone to fracture under high injection pressure. This study presents a novel salt core technique to overcome this constraint. The core is fabricated using a sugar-based syrup with an optimized sugar-to-salt ratio, and a balanced mix of coarse and fine salt particles to reduce voids and improve structural compactness. The method’s effectiveness is demonstrated through successful molding of a Tri-Ring connector, a part typically difficult to produce integrally. Core shift behavior was analyzed through CAE simulations and confirmed by experimental validation. The dimensional precision of the molded product was further optimized using the Taguchi method. This work highlights a sustainable and practical solution for producing complex, high-precision molded parts without assembly.

Water scarcity and irregular rainfall pose significant challenges to irrigation, especially for small-scale farmers. This study presents the development of an eco-friendly, cellulose-based hydrogel using agricultural waste such as sugarcane bagasse and pea peels aimed at improving soil moisture retention. Cellulose was extracted via alkali treatment, aligning with principles of waste valorization and the circular economy. The hydrogel was synthesized using carboxymethyl cellulose sodium (CMCNa) and xanthan gum with citric acid as a biodegradable crosslinker. Cellulose nanocrystals (CNC’s), obtained through acid hydrolysis, were incorporated to enhance structural integrity. The hydrogel was characterized through Fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and energy-dispersive spectroscopy (EDS). It demonstrated excellent swelling capacity, sustained moisture retention, and biodegradability. Soil amended with the hydrogel retained 67 % of moisture after 15 days compared to 50 % in control soil and supported enhanced plant growth (26.9 cm of height vs. 20.7 cm in control). Biodegradability tests indicated 20 % degradation within 2 weeks. These results show that the hydrogel offers a cost-effective and sustainable approach to irrigation management, with strong potential for application in drought-prone agricultural areas.