Yuan Feng

Mechanical stress is a fundamental aspect of soft tissues that influences cellular behavior and tissue integrity, yet noninvasive imaging of stress in vivo remains a major challenge. Conventional magnetic resonance elastography (MRE) measures tissue stiffness but not stress. Employing a physics-informed model, we analyze reverberant shear wave fields recorded by MRE to capture the 3D mapping of tissue stress. By decomposing reverberant waves into anisotropic traveling wave components, we establish a direct relationship between wave speed, polarization, and local stress, without requiring wave direction knowledge. This method was validated with numerical simulations and phantom experiments. Applied to patients with meningiomas and pituitary adenomas, it generated high-resolution stress maps consistent with anatomy and physiology. Cortical stress measurements enabled intracranial pressure estimation, uncovering trends related to patient age and pathology. Our results demonstrate that noninvasive stress imaging provides a novel quantitative biomarker for mechanobiological research and suggests new possibilities for clinical applications.

Structural and functional heterogeneity is a defining feature of natural tissues, facilitating ordered integration of different tissue components through extracellular matrix (ECM) mediated intercellular communication and ultimately enabling responsive, collective movements. Nevertheless, the fabrication of functionally engineered, heterogeneous tissue‐mimicking materials capable of achieving intercellular communication‐assisted movements remains a major challenge in bottom‐up synthetic biology. Here, we co‐assemble enzyme‐ or magnetic nanoparticle‐encapsulated protocells into hierarchical prototissues with structural and functional heterogeneity using a modular, extra‐protocellular matrix (EPCM)‐assisted integration method. The prototissues exhibit enzyme‐powered buoyancy through the generation of oxygen by an inter‐protocellular glucose oxidase–catalase cascade reaction and the accumulation of oxygen bubbles within the matrix. In addition, the incorporation of magnetically responsive protocells endows the system with magnetically controllable motion. By orderly integrating chemical and physical responsive modules through EPCM, we achieve controlled underwater oscillation and shape change. Overall, our approach establishes heterogeneous functional prototissues with controllable motility and deformation capabilities, providing a model system for chemical‐physical stimulus‐responsive behaviors and spatial reconfiguration, and offering opportunities for bottom‐up synthetic biology and tissue engineering.

Magnetic resonance elastography (MRE) enables non‐invasive assessment of the mechanical properties of brain tissue, which is crucial for diagnosing neurodegenerative diseases and understanding brain development. This technique relies on inducing controlled harmonic deformation in brain tissue and detecting the resulting motion via motion‐sensitive magnetic resonance imaging (MRI) sequences. Electromagnetic actuators, which leverage the static magnetic field of MRI scanners and Lorentz law to generate rotary vibration, offer a cost‐effective solution for brain MRE. However, their application in brain MRE requires addressing MRI safety challenges from metallic components and coil positioning inflexibility. Here, we present a comprehensive protocol for designing, constructing, and implementing an electromagnetic actuator tailored for brain MRE experiments. We detail key considerations including design of an actuator capable of reducing electromagnetic interference and vibration stimulation, construction of a controller for the actuator, design schematic of an MRE sequence, and methods for obtaining final mechanical results of MRE. This protocol aims to provide a practical guide for research laboratories seeking to develop MRE systems, facilitating accurate and reproducible assessment of brain mechanical properties for both basic research and clinical translation. © 2026 Wiley Periodicals LLC. Basic Protocol : Design, construction, and implementation of an electromagnetic MRE actuator for brain MRE

Conventional drug delivery routes, such as oral and injectable administration, often suffer from poor targeting, systemic side effects, and limited control over drug release. Magnetically guided microrobots have emerged as a promising solution by enabling minimally invasive navigation, precise localization, and controllable cargo delivery in complex biological environments. Recent advances in microfabrication, biomaterials, and magnetic actuation have led to diverse microrobot designs, including helical swimmers and biohybrid systems incorporating red blood cells, bacteria, algae, or exosomes. These microrobots can transport drugs, cells, or theranostic agents, with release triggered by magnetic, chemical, optical, or acoustic stimuli. In parallel, progress in imaging and tracking technologies, such as ultrasound, photoacoustic imaging, X‐ray, and MRI, has enabled real‐time guidance and monitoring in vivo. Despite encouraging proof‐of‐concept studies, several challenges hinder clinical translation. These include limited biocompatibility, reduced locomotion efficiency under physiological flow, insufficient release precision, and regulatory constraints. Future development requires safer and more robust materials, multimodal imaging strategies for accurate navigation, and scalable fabrication methods that meet medical standards. With continued integration of engineering and biomedical research, magnetically guided microrobots hold strong potential for targeted therapy, regenerative medicine, and minimally invasive treatment, representing a significant advance in precision drug delivery.

The in vivo characterization of biomechanical properties in soft biological tissues offers critical insights for both scientific research and clinical diagnostics. Magnetic resonance elastography (MRE) is a noninvasive technique that enables 3D measurements of the biomechanical properties of various soft tissues. While numerous inversion algorithms have been developed based on wave fields from MRE, robust and multi-parameter estimation of biomechanical properties remains an area of active development. Here we present comprehensive MRE datasets, including phantom, human liver, and human brain data. The phantom data serves as a benchmark for validation, while the liver and brain datasets represent typical application scenarios for MRE. All wave images were acquired using 3 T scanners, ensuring high-quality data. Additionally, a state-of-the-art inversion algorithm, the Traveling Wave Expansion-Based Neural Network (TWENN), is also provided for comparative analysis. These datasets provide a diverse range of application scenarios, facilitating the development and refinement of MRE inversion algorithms. By making these resources available, we aim to advance the field of MRE research and improve the inversion of biomechanical parameters.

Stereotactic neurointervention is a common procedure for biopsy, injection, ablation, and implantation of electrodes for deep brain stimulation. Guided by preoperative imaging, conventional approaches are mostly performed manually, lacking operation stability and interactive feedback. The intraoperative magnetic resonance imaging (MRI) guidance enables both structural and functional assessment during operation, permitting interactive adaptation to tissue deformation and avoidance of critical anatomical regions. Here, we report an MRI-guided robotic system for stereotactic neurointervention. A macro-micro hybrid pneumatic-hydraulic actuated stereotactic robot with a large range of motion and high precision is developed. This is coupled with a compact bioinspired soft actuator for target intervention. A global-focal MRI sequence is proposed for interactive navigation, closed-loop control, and precise targeting. Validation is performed with phantom, cadaveric, and in vivo animal studies, showing positional accuracies of 0.39, 0.68, and 0.14 millimeters, respectively, demonstrating superior performance compared to the current state of the art in robotic-assisted stereotactic neurointervention.