Wei Gao

Precise and programmable mechanical stimulation is essential for constructing defined cellular microenvironments, yet existing in vitro stretching platforms often suffer from limited control over biaxial strain fields and reliable strain transfer. Here, we present a magnetically driven hydrogel–elastomer composite consisting of an auxetic-like inward-concave chamfered hard-magnetic soft actuator and a central GelMA matrix. Under a parallel magnetic field, the actuator undergoes in-plane expansion, transferring an approximately 10% near-equibiaxial strain to the hydrogel. Benzophenone-mediated interface modification enhances hydrogel–elastomer adhesion and improves interfacial strain-transfer capability. Finite-element-guided geometric optimization identifies a 3 mm inward-concave chamfered design that balances corner constraint reduction and auxetic-like deformation coupling. In a proof-of-concept cell-culture demonstration, RAW264.7 macrophages cultured on the platform exhibited heterogeneous morphological changes and F-actin reorganization during cyclic near-equibiaxial stimulation, supporting the feasibility of the platform for controlled cellular mechanical stimulation. This composite provides a magnetically programmable platform for soft-material deformation and mechanobiological applications.

Compression–torsion coupled metamaterials provide a geometry-driven approach for motion conversion and wave regulation. This study proposes a spatial curved-rod compression–torsion coupled metastructure and develops a reduced-order equivalent stiffness model with axial displacement and rotational angle as the generalized degrees of freedom. The equivalent stiffness matrix, derived from the curved-rod centerline geometry through a strain-energy formulation, is incorporated into a one-dimensional Bloch model to characterize low-frequency wave propagation. The results show that the off-diagonal coupling stiffness governs the compression-induced rotational response of the unit cell and significantly affects the frequencies and modal compositions of the two lowest dispersion branches. Finite element simulations and experiments validate the predicted stiffness and compression–torsion response, while acceleration transmissibility measurements of a finite periodic chain are consistent with the theoretical dispersion characteristics. The reduced-order model captures the overall behavior of the two lowest branches and clarifies the role of compression–torsion coupling stiffness in branch separation and modal composition, although the higher branch is less accurately predicted owing to the lumped inertia approximation. The proposed design provides a lightweight strategy for low-frequency wave regulation through structural coupling.

The Faraday instability of shallow particle-laden liquids under geometric confinement was investigated through combined experimental and theoretical analyses. Water-based suspensions containing micrometer-sized magnetite particles were vertically excited in a cylindrical container, and the effects of particle mass, particle size, and fluid depth on the threshold acceleration and axisymmetric modal responses were examined. Particle loading increased the instability threshold, with the threshold acceleration increasing by up to 29% as the particle mass was increased from 0.05 to 0.15 g. Although the overall particle volume fraction was low, sedimentation formed a basal particle layer near the container bottom. A modified baseline force-detuning-based model with nominal effective-property corrections captures the modal ordering and the overall instability characteristics of shallow particle-laden liquids. Comparison with the experimental results further suggests that sedimented-particle-bed dissipation contributes to the additional threshold increase observed at larger particle masses, larger particle sizes, and higher-order modes.

Magnetorheological elastomers (MREs) are advanced smart materials composed of magnetosensitive particles embedded in a flexible matrix, where the particle distribution and properties significantly influence their mechanical and electromagnetic behaviors. In this study, layered MRE samples with alternating soft and hard magnetic particle layers were fabricated using 3D printing and subjected to a comprehensive investigation of their deformation and electromagnetic absorption characteristics. Experimental tests and finite element simulations revealed that the deformation capacity of MREs is primarily governed by the arrangement of soft and hard magnetic layers. This reflects a complex interplay among the material’s Young’s modulus, the magnitude and direction of the applied magnetic field, and the orientation of remanent magnetization. Notably, the compression modulus does not always increase with field strength; when the remanent magnetization opposes the magnetic field, the modulus decreases as the field intensifies. Furthermore, the electromagnetic wave absorption properties of the MREs were found to improve with higher percentages of soft magnetic materials, with the SHS-type materials demonstrating enhanced absorption bandwidth and peak absorption values. These results offer critical insights for optimizing the design and performance of MREs in applications requiring tunable mechanical and electromagnetic properties.

In this paper, a novel magnetorheological elastomer (MRE) isolator with a compression-torsion structure was developed to address existing challenges related to stiffness variation, damping force, and magnetic control range. Through performance testing of the vibration isolator prototype and theoretical analysis based on traditional magnetic dipole model of the MRE, the effects of applied magnetic field and compression displacement on the performance of the designed MRE isolator were systematically evaluated. The results showed that integrating the compression-torsion structure not only enhances the magneto-induced mechanical performance of the MRE but also improves the overall performance of the entire MRE isolator. The output force of the MRE isolator with a compression-torsion structure generally surpasses than that of the MRE isolator lacking this feature. The isolator’s stiffness can vary by up to 119% compared to its initial stiffness when a 2 A current is applied at a compression displacement of 0.5 mm. The proposed design, combining the compression-torsion structure and the MRE isolator, offers new insights for future research and applications in the realm of MRE isolators.

Improving the performance of flexible eddy current (EC) probes (FECPs) is a current research hotspot. Thus, a novel FECP, fractal EC sensor technology is proposed. This FECP can enhance the consistency of the probe for detecting short cracks in different orientations by changing the coil structure of the probe, thereby reducing the probability of missing the particular direction cracks. However, due to the limit of the wires’ layout space, an issue remains: the fractal probe’s signal output is weak. To break through this limitation, this study proposes a method to achieve the passive amplification of the output signal of FECPs. A layer of homemade flexible sheet doped with pure iron particles is covered on a flexible Koch differential pick-up fractal EC probe. First, the manufacturing details of the flexible sheet and probe are provided; then, the influence of the probes with and without sheet on the amplification of the crack detection signals is compared via finite element analysis and experiment. The results show that the probe with the sheet can realize the passive amplification to the crack signals in C-scan experimental results of 28 kinds of cracks, and under the excitation frequencies of 50, 100, and 1000 kHz, the signal amplitudes output from the probe with sheet increase by at least 12.8%, 27.6%, and 40.4%, respectively.

Magneto-active soft materials fabricated by new paradigms of 3D printing have received considerable interest for various applications owing to their remarkable complex deformation and extraordinary magneto-mechanical properties. The morphology and magneto-mechanical properties of materials prepared by direct ink writing (DIW) 3D printing, on the other hand, are closely related to process and material parameters that are critical in this printing technique. In this study, the morphology of ink filaments printed under different parameters was investigated through theoretical analysis and experimental tests to achieve the implementation. The results demonstrated that the prepared magnetic inks are suitable for DIW, and the predictions based on a simplified hydrodynamic model are basically consistent with the measured data in the experiments. It also showed that the diameter of the extruded ink filaments increases with increasing extrusion pressure, and decreasing printing speed, layer height, and magnetic particle content. Similarly, the magnetic property varies with the nozzle diameter and material composition variations. Using the obtained optimal parameters, several magneto-active rods and plate-like structures with a specific arrangement of microscopic magnetic domains were successfully fabricated. Their magnetically driven behavior further was investigated experimentally and numerically, which revealed a programmed, non-contact remote control, reversible, and multimodal large deformation characteristics. The findings of this study allow a more in-depth understanding and analysis of processing-structure-property correlations of printed magneto-active soft materials, laying the groundwork for personalized customization and versatile development of magneto-mechanical performance.