The robotic fish has attracted widespread research interest over the past few decades, due to its outstanding agility and environmental friendliness. And the sensing ability of underwater environments is crucial for the robotic fish to accomplish various underwater tasks. Inspired by the lateral line of real fish, many types of artificial lateral line (ALL)sensors have been proposed, including pressure-based sensors and deformation-based sensors. However, currently these types of ALL sensors mounted on robotic fish are susceptible to the interference from robotic fish’s self-motions such as yaw motion and pitch motion, as well as the unavoidable vortices around the robotic fish. To address the above issues, a deformation-based magnetic ALL sensor capable of flow velocity-decoupling sensing is proposed, which can be used to measure the swimming speed of the robotic fish while suppressing the aforementioned noise. Besides, an ALL array is designed and mounted on both sides of a robotic fish, enabling the measurement of its swimming speed under both rectilinear and turning motion, with a mean absolute error (MAE) of 0.0153 m/s and 0.0125 m/s, respectively. Based on this, the ALL array is applied for trajectory estimation of the robotic fish, and the MAE of trajectory estimation under rectilinear and turning motion is 0.0600 m and 0.0730 m, respectively.

ABSTRACT Magnetic tactile sensor with centripetally magnetization designs is capable of efficient 3D force decoupling sensing, which is essential for advancing robotic dexterity. Nevertheless, the miniaturization of sensors remains a challenge, primarily due to the complexities associated with precisely fabricating such planar magnetic structures. Here, we present a laser‐assisted folding and magnetization (LAFM) method to create centripetally magnetized films. Laser‐etched grooves enable controlled folding, achieving accurate magnetization alignment in films as small as 5 × 5 mm2, which are verified by root mean square errors (RMSEs) of less than 5 µT between the experimental and theoretical magnetic field values. This breakthrough enabled the compact 3D force sensor featuring high force resolution (tangential 3 mN, normal 9 mN), rapid response (34 ms), and long‐term stability (>2500 cycles, <1% deviation). When installed on a mobile manipulator, the sensor enables adaptive grasping of delicate objects during obstacle traversal. Its functionality is further enhanced by deploying an array of 16 units on a dexterous hand, which supports non‐destructive stiffness recognition across six representative materials and stable manipulation of variable‐mass or irregular objects. This work establishes a robust pathway for miniaturized tactile sensors and embodied intelligence, especially in robotic perception.

Magnetic functional soft materials featuring hard-magnetic particles enable sophisticated actuation and sensing, yet traditional magnetic field-assisted digital light processing (DLP) often struggles with limited magnetic performance and processing difficulties at high particle loadings. This work introduces a rotating magnetic field into the DLP process to enhance the manufacturing capability and magnetic properties of the fabricated structures. We systematically investigate the influence of the rotating magnetic field frequency on the material's magnetic performance, identifying an optimal frequency range through experimental validation. Under low magnetic loading conditions, a localized enrichment effect of magnetic particles driven by continuous alignment is observed, which significantly impacts the fabrication quality. To quantitatively assess the manufacturing outcomes, a dual-indicator evaluation standard enabling a comprehensive analysis of both particle dispersion and alignment effectiveness is proposed. By applying the frequency optimization strategy derived from these empirical insights, the 20 wt% magnetic composites achieve a remanence of 18.49 emu/g, corresponding to 72.97% of the saturation remanence. As the magnetic content increases, the sensitivity of the dual indicators to the field frequency becomes more pronounced, highlighting the critical role of the rotating magnetic field in high-loading conditions. Finally, a magnetic actuator with a 20 wt% magnetic content and complex magnetization arrangement was fabricated. The successful realization of its intended functions confirms the precision and reliability of the proposed manufacturing method. This work provides a crucial optimization framework for leveraging the potential of rotating magnetic fields in advanced magnetic manufacturing.

Magnetic functional soft materials using hard-magnetic particles as inlays exhibit remarkable actuation and sensing performance, enabled by continuously evolving fabrication methods that achieve sophisticated structural and magnetization designs. Among these, magnetic field-assisted digital light processing (MFA-DLP) offers unique advantages in material design freedom, yet faces challenges including low remanence due to incomplete alignment and printing defects caused by pre-magnetized particles' aggregation. To address these limitations, this work proposes a dynamic magnetic field-assisted DLP (DMFA-DLP) method, where time-varying fields induce particle-level rotational dynamics and overcome interparticle attractive barriers, thereby ensuring homogeneous particle dispersion before each alignment cycle. Through such strategy, this approach enhances alignment efficiency, mitigates aggregation accumulation, and guarantees consistency across multiple alignment processes. Experimental results demonstrate that this method effectively improves alignment efficiency and boosts remanence, even doubling the alignment ratio (212%) at weaker alignment field. Various samples featuring complex structures and magnetic arrangements are fabricated to validate the method's manufacturing capability and enhanced reliability. A 10-mm-diameter, 24-pole magnetic ring is successfully produced and implemented as an angle sensor, demonstrating the method's capacity for fabricating high-resolution multi-directional magnetic patterns. This work overcomes fundamental limitations of MFA-DLP, establishing a robust platform for high-performance magnetic soft material manufacturing.

As one of the inherent characteristics of cell, density is a significant biomarker for the analysis and investigation of multiple cellular events. Density profiles of cell populations are informative data concerning physiological research such as differentiation, live-death assay, aging, immune response, or drug resistance (Durmus et al. in Proc Natl Acad Sci 112:3661–3668, 2015). The fast-speed, low-cost, and high-resolution measurement of single-cell level density plays a vital role in cell type recognition and detection of minute changes in cell properties, which indicates the cells' responses to the physical surroundings. Based on the density profiles of cell populations, further avalanche applications spanning over separation and sorting, manipulations, 3D cell culture, and point-of-care diagnosis are possible.

The advancements in tactile sensor technology have found wide-ranging applications in robotic fields, resulting in remarkable achievements in object manipulation and overall human-machine interactions. However, the widespread availability of high-resolution tactile skins remains limited, due to the challenges of incorporating large-sized, robust sensing units and increased wiring complexity. One approach to achieve high-resolution and robust tactile skins is to integrate a limited number of sensor units (taxels) into a flexible surface material and leverage signal processing techniques to achieve super-resolution sensing. Here, we present a magnetic skin consisting of multi-direction magnetized flexible films and a contactless Hall sensor array. The key features of the proposed sensor include the specific magnetization arrangement, K-Nearest Neighbors (KNN) clustering algorithm and convolutional neural network (CNN) model for signal processing. Using only an array of 4*4 taxels, our magnetic skin is capable of achieving super-resolution perception over an area of 48400 mm2, with an average localization error of 1.2 mm. By employing neural network algorithms to decouple the multi-dimensional signals, the skin can achieve multi-point and multi-scale perception. We also demonstrate the promising potentials of the proposed sensor in intelligent control, by simultaneously controlling two vehicles with trajectory mapping on the magnetic skin.

The magnetic levitation method, characterized by its simplicity, absence of sample magnetization requirements, and convenient operation, has found extensive applications not only in fields such as chemical analysis, biological measurements, and performance characterization but also in the non-contact manipulation of small-sized weakly magnetic materials. The ability to manipulate samples, whether at macroscopic, mesoscopic, or microscopic scales, forms the foundation and key to scientific research and development. In recent years, non-contact manipulation and performance characterization techniques for various materials have gained popularity due to the potential impact of physical contact-based clamping tools on the surface morphology or properties of materials. Consequently, theoretical research and technological applications related to non-contact manipulation have experienced significant advancements. Currently, several forms of non-contact manipulation techniques are available for the manipulation of small-sized samples or structures.

Novel testing method is an important research direction in the field of mechanical engineering. Magnetic levitation testing method has proved its advantages of high accuracy and sensitivity in density-based analysis. Therefore, trials in testing materials and products for materials processing using magnetic levitation have achieved series of progress.

In contrast with jumping robots made from rigid materials, soft jumpers composed of compliant and elastically deformable materials exhibit superior impact resistance and mechanically robust functionality. However, recent efforts to create stimuli-responsive jumpers from soft materials were limited in their response speed, takeoff velocity, and travel distance. Here, we report a magnetic-driven, ultrafast bistable soft jumper that exhibits good jumping capability (jumping more than 108 body heights with a takeoff velocity of more than 2 meters per second) and fast response time (less than 15 milliseconds) compared with previous soft jumping robots. The snap-through transitions between bistable states form a repeatable loop that harnesses the ultrafast release of stored elastic energy. On the basis of the dynamic analysis, the multimodal locomotion of the bistable soft jumper can be realized: the interwell mode of jumping and the intrawell mode of hopping. These modes are controlled by adjusting the duration and strength of the magnetic field, which endows the bistable soft jumper with robust locomotion capabilities. In addition, it is capable of jumping omnidirectionally with tunable heights and distances. To demonstrate its capability in complex environments, a realistic pipeline with amphibious terrain was established. The jumper successfully finished a simulative task of cleansing water through a pipeline. The design principle and actuating mechanism of the bistable soft jumper can be further extended for other flexible systems.

Magnetic flexible actuators with hard-magnetic particles (NdFeB) as inlays have attracted widespread attention due to their small size, wireless control capability, and diverse transformation modes. The manufacturing method of these actuators plays a crucial role in their functionality. Here we propose a magnetic field-assisted manufacturing method based on vat photopolymerization (VPP) to produce hard-magnetic flexible actuators with 3D architecture in both geometry structure and magnetization arrangements. The assisting magnetic field enables alignment of hard magnetic particles during manufacturing process, thus obtaining a magnetization arrangement. The VPP method offers the ability to manufacture fine structures and selective curing but has a limitation on the magnetic particle content. To deal with the lack of driving force due to the low available content of magnetic particles, we construct groove structure to enhance the actuators' deformation, which is confirmed by both theoretical and experimental analyses. Flexible actuators with a low magnetic particle content (10 wt%) can be fabricated and fulfill intended functionality. We demonstrate the effectiveness of our method by manufacturing multi-arm grippers, showcasing their transportation capabilities. Moreover, we construct a 2-DOF joint for a crawling robot, significantly improving its motion performance and increasing the average step length to 6.8 times. Finally, we design and manufacture a magnetic diaphragm with complex structure and 3D magnetization arrangements, which is applied to a micro pump, demonstrating its pumping process with a rate of about 3.6 mL/min. These results highlight the potential of the proposed method in designing complex structures and magnetization arrangements of flexible actuators, expanding their functional boundaries.

Flexible Electronics In article number 2310145, Huangzhe Dai, Chengqian Zhang, Peng Zhao, and co-workers present a magnetic tactile sensor with 3D decoupling perception for arbitrary forces through magnetic field signal of a centripetally magnetized film elegantly designed based on their original 3D decoupling theory. Leveraging the inherent advantages of wireless penetrability, this sensor showcases its potential to endow robots with tactile sense comparable to that of human skin in any scenario.

Non-contact manipulation and measurement of cells are the major concerns in the biomedical field. However, the existing methods are limited by the physical properties of cells, and may cause damages to the cells. This paper proposes an original non-contact manipulation and measurement method by magnetic levitation. Based on the configuration of two ring magnets with like poles facing each other, the cells can aggregate and levitate in the paramagnetic medium. The mathematical model was established to analyze the distributions of magnetic fields and movements of cells for the first time. Theoretical and experimental results show that the magnetic levitation method can be adaptive to the cells by tuning the size of the configuration. The three-dimensional cell clusters were formed and the average densities of 3T3, MDA, B16 and 4T1 cells were measured as 1.074 ± 0.005 g/cm3, 1.084 ± 0.003 g/cm3, 1.079 ± 0.002 g/cm3 and 1.124 ± 0.003 g/cm3 respectively. Moreover, the dead cells and living cells were distinguished based on the levitating heights. The results indicate that the proposed magnetic levitation method is promising for the three-dimensional culture and rapid measurement of cells.

Tactile sensory organs for sensing 3D force, such as human skin and fish lateral lines, are indispensable for organisms. With their sensory properties enhanced by layered structures, typical sensory organs can achieve excellent perception as well as protection under frequent mechanical contact. Here, inspired by these layered structures, a split‐type magnetic soft tactile sensor with wireless 3D force sensing and a high accuracy (1.33%) fabricated by developing a centripetal magnetization arrangement and theoretical decoupling model is introduced. The 3D force decoupling capability enables it to achieve a perception close to that of human skin in multiple dimensions without complex calibration. Benefiting from the 3D force decoupling capability and split design with a long effective distance (>20 mm), several sensors are assembled in air and water to achieve delicate robotic operation and water flow‐based navigation with an offset <1.03%, illustrating the extensive potential of magnetic tactile sensors in flexible electronics, human‒machine interactions, and bionic robots.

Magnetic actuation has emerged as a prominent method in soft robots due to its charming advantages on diverse magnetization designs, which heavily rely on the microstructures formed by hard magnetic particles (NdFeB) inside the robot. However, the contradiction between the need for multiple orientations of the particles and the issue of particle agglomeration caused by repeated orientation during fabrication has not been effectively resolved. This limitation prevents additive manufacturing of high-performance magnetic soft robots and hinders further diversification of robot magnetization structures. In this study, we proposed a method that utilizes a dynamic magnetic field to re-disperse agglomerated particles. This method is able to effectively disperse the agglomerates uniformly and enhance the re-oriented particle chains in multiple aspects, including compactness, orientation (similar to 200 %), and maintenance time (>120 min). Furthermore, this method was utilized to improve the magneto-induced deformation (from 7.71 to 13.89) of the Magneto-Rheological Elastomer (MRE) samples, which were fabricated with repeatedly orientated magnetizations using magnetic field-assisted Stereo-lithography (SLA). Overall, the proposed method lays the groundwork for the structural complexity of magnetic soft robots and holds significant potential for broadening the fabrication methods of magnetic soft robots.

Abstract Tactile sensory organs for three-dimensional (3D) force, such as human skin and fish's lateral line, are indispensable for creatures. Empowered by their often layered structure, typical sensory organs can achieve excellent perception as well as protection when facing frequent mechanical contact. Here, inspired by these layered structures, we introduce a split-type flexible magnetic tactile sensor with wireless sensing for 3D force with high accuracy (0.83%), through developing centripetal magnetization arrangement and theoretical decoupling model. Adjustable sensing performance is obtained to adapt to specific application scenarios by employing buffer layers with corresponding properties. Benefiting from the split design with long effective distance (> 20 mm) and replaceable buffer layer, several sensors are assembled in air and water to achieve delicate robotic operation and water flow-based navigation with offset < 0.65%, illustrating broad potential of magnetic tactile sensors in flexible electronics, human-machine interaction, and bionic robots.

Tactile recognition is among the basic survival skills of human beings, and advances in tactile sensor technology have been adopted in various fields, bringing benefits such as outstanding performance in manipulating objects and general human-robot interactions. However, promoting enhanced perception of the existing tactile sensors is limited by their sensor array arrangement and wire-connected design. Here we present a wireless flexible magnetic tactile sensor (FMTS) consisting of a multidirection magnetized flexible film (perception module) and a contactless Hall sensor (signal receiving module). The flexible magnetic film is composed of NdFeB microparticles and soft silicone elastomer microparticles, and it transfers the unambiguous transduction of external force position and magnitude into magnetic signals. Benefiting from the specific magnetization arrangement and clustering algorithm, only one Hall sensor is needed in FMTS to perceive the magnitude and position of the contact spot simultaneously with super-resolution (2.1 mm average error) on a large area (3600 mm2), and the effective working distance is also greatly extended (∼30 mm), allowing for the full softness and adaptability to diverse conditions. We anticipate that this design will promote the development of soft tactile sensors and their integration into human-robot interaction and humanoid robot perception.

The development of flexible tactile sensors is an emerging field due to their wide applications ranging from human-robot interactions to wearable electronics. This paper proposes a flexible tactile sensor based on the magnetic field for detecting both forces and positions, which exhibited a linear relationship. The direct ink writing technology was used to fabricate magnetic elastomers for the quick test of variable patterns. The introduced folding magnetization allows for a higher magnetic flux density in the designated position which made it possible to get rid of magnets. A pattern was designed and printed. The linear relationship was found to be linear (R-2 > 0.98) between the magnetic field signal and the magnitude and position of the load force. Moreover, the untethered sensor was proven to work well in the sealed box, which is expected to serve as the electrical skin of robots or the tactile sensor in extreme environments. (C) 2021 Elsevier B.V. All rights reserved.

Soft actuators are attracting increasing attention for their great potentials in transportation, exploration and clinical treatments, especially the magnetic-driven soft actuators powered by magnetic energy wirelessly. However, the further promotion of complicated three-dimensional magnetic-driven soft actuators with multiple applications is limited by the simple designs and limited locomotion. This paper introduces the work integrating the ancient origami craft and the magnetic-driven materials, which regulates the conversion from external magnetic energy into inner elastic energy of magnetic materials, broadening the designs and functions of magnetic-driven actuators. The results show that the origami method can program the directions of magnetic moments in the soft actuators and adjust the amplitudes of deformation, which lays the foundation for designing magnetic-driven actuators with complicated three-dimensional structures. Especially, a rolling robot that can contract its body up to 65% of the original length is fabricated by origami method, which possesses the impressive ability of obstacle surmounting. Furthermore, a new three-dimensional soft aperture which can be powered wirelessly by magnetic energy was demonstrated as a supplement of present wired aperture. The results show that the origami method of magnetic-driven soft actuators could broaden the designs of magnetic-driven actuators, which promotes the applications in environment detection, targeted drug transport, flexible optical elements and so on.