Magnetic-actuated hydrogel microrobots with multimodal motion and collective behavior.

Magnetic-actuated miniature robots have sparked growing interest owing to their promising potential in biomedical applications, such as noninvasive diagnosis, cargo delivery, and microsurgery. Innovations are required to combine biodegradable materials with flexible mobility to promote the translation of magnetic robots towards in vivo application. This study proposes a biodegradable magnetic hydrogel robot (MHR) with multimodal locomotion and collective behavior through magnetic-assisted fabrication. The MHRs with aligned magnetic chains inside their structures have more significant maximum motion speeds under rotating magnetic fields than the robots without magnetic alignment. By reconfiguring the external magnetic fields, three types of stable motion modes (tumbling, spinning, and wobbling modes) of the individual MHRs can be triggered, while flexible conversion can be achieved between each motion mode. The motion mechanism of each motion mode under diverse rotating magnetic fields has been analyzed. The collective behavior of the MHRs, which is triggered by the magnetic dipole force, can enhance the motion performance and pass through sophisticated terrains. Furthermore, the experimental results demonstrate that the assembled MHRs can execute complicated tasks such as targeted cargo delivery. The proposed MHRs with multimodal locomotion and assembled behavior show effective motion efficiency, flexible maneuverability, and remarkable targeting ability, providing a new choice for magnetic robots in biomedical applications.

Magnetic steering continuum robot for transluminal procedures with programmable shape and functionalities.

Millimeter-scale soft continuum robots offer safety and adaptability in transluminal procedures due to their passive compliance, but this feature necessitates interactions with surrounding lumina, leading to potential medical risks and restricted mobility. Here, we introduce a millimeter-scale continuum robot, enabling apical extension while maintaining structural stability. Utilizing phase transition components, the robot executes cycles of tip-based elongation, steered accurately through programmable magnetic fields. Each motion cycle features a solid-like backbone for stability, and a liquid-like component for advancement, thereby enabling autonomous shaping without reliance on environmental interactions. Together with clinical imaging technologies, we demonstrate the capability of navigating through tortuous and fragile lumina to transport microsurgical tools. Once it reaches larger anatomical spaces such as stomach, it can morph into functional 3D structures that serve as surgical tools or sensing units, overcoming the constraints of initially narrow pathways. By leveraging this design paradigm, we anticipate enhanced safety, multi-functionality, and cooperative capabilities among millimeter-scale continuum robots, opening new avenues for transluminal robotic surgery.

Biodegradable Magnetic Hydrogel Robot with Multimodal Locomotion for Targeted Cargo Delivery.

Recent strides in the development of untethered miniature robots have shown the advantages of diverse actuation methods, flexible maneuverability, and precise locomotion control, which has made miniature robots attractive for biomedical applications such as drug delivery, minimally invasive surgery, and disease diagnosis. However, biocompatibility and environmental adaptability are among the challenges for further in vivo applications of miniature robots due to the sophisticated physiological environment. Herein, we propose a biodegradable magnetic hydrogel robot (BMHR) that possesses precise locomotion with four stable motion modes, namely tumbling mode, precession mode, spinning-XY mode, and spinning-Z mode. Using a homemade vision-guided magnetic driving system, the BMHR can achieve flexible conversion between the different motion modes to cope with changes in complex environments, and its superior ability to cross obstacles is demonstrated. In addition, the transformation mechanism between different motion modes is analyzed and simulated. Benefiting from the diverse motion modes, the proposed BMHR has promising applications in drug delivery, showing remarkable effectiveness in targeted cargo delivery. The BMHR's biocompatible property, multimodal locomotion, and functionality with drug-loaded particles can provide a new perspective to combine miniature robots with biomedical applications.

Scale-reconfigurable miniature ferrofluidic robots for negotiating sharply variable spaces.

Magnetic miniature soft robots have shown great potential for facilitating biomedical applications by minimizing invasiveness and possible physical damage. However, researchers have mainly focused on fixed-size robots, with their active locomotion accessible only when the cross-sectional dimension of these confined spaces is comparable to that of the robot. Here, we realize the scale-reconfigurable miniature ferrofluidic robots (SMFRs) based on ferrofluid droplets and propose a series of control strategies for reconfiguring SMFR's scale and deformation to achieve trans-scale motion control by designing a multiscale magnetic miniature robot actuation (M3RA) system. The results showed that SMFRs, varying from centimeters to a few micrometers, leveraged diverse capabilities, such as locomotion in structured environments, deformation to squeeze through gaps, and even reversible scale reconfiguration for navigating sharply variable spaces. A miniature robot system with these capabilities combined is promising to be applied in future wireless medical robots inside confined regions of the human body.

Magnetically actuated intelligent hydrogel-based child-parent microrobots for targeted drug delivery.

Small intestine-targeted drug delivery by oral administration has aroused the growing interest of researchers. In this work, the child-parent microrobot (CPM) as a vehicle protects the child microrobots (CMs) under a gastric acid environment and releases them in the small intestinal environment. The intelligent hydrogel-based CPMs with sphere, mushroom, red blood cell, and teardrop shapes are fabricated by an extrusion-dripping method. The CPMs package uniform CMs, which are fabricated by designed microfluidic (MF) devices. The fabrication mechanism and tunability of CMs and CPMs with different sizes and shapes are analyzed, modeled, and simulated. The shape of CPM can affect its drug release efficiency and kinetic characteristics. A vision-feedback magnetic driving system (VMDS) actuates and navigates CPM along the predefined path to the destination and continuously releases drug in the simulated intestinal fluid (SIF, a low Reynolds number (Re) regime) using a new motion control method with the tracking-learning-detection (TLD) algorithm. The newly designed CPM combines the advantages of powerful propulsion, good biocompatibility, and remarkable drug loading and release capacity at the intestinal level, which is expected to be competent for oral administration of small intestine-targeted therapy in the future.

Autonomous Biohybrid Urchin-Like Microperforator for Intracellular Payload Delivery.

A magnetic urchin-like microswimmer based on sunflower pollen grain (SPG) that can pierce the cancer cell membrane and actively deliver therapeutic drugs is reported. These drug loaded microperforators are fabricated on a large scale by sequentially treating the natural SPGs with acidolysis, sputtering, and vacuum loading. The microswimmers exhibit precise autonomous navigation and obstacle avoidance in complex environments via association with artificial intelligence. Assemblies of microswimmers can further enhance individual motion performance and adaptability to complicated environments. Additionally, the experimental results demonstrate that microswimmers with nanospikes can accomplish single-cell perforation for direct delivery under an external rotating magnetic field. Drugs encapsulated in the inner cavity of the microperforators can be accurately delivered to a specific site via remote control. These dual-action microswimmers demonstrate good biocompatibility, high intelligence, precision in single-cell targeting, and sufficient drug loading, presenting a promising avenue for many varieties of biomedical applications.