june W

Nature, Published online: 22 November 2024; doi:10.1038/d41586-024-03872-7

Nature Methods, Published online: 06 December 2024; doi:10.1038/s41592-024-02548-4

Miniature Soft Robots for Targeted Combination Therapy

Miniature robots have great prospects to transform targeted drug delivery. In article number 2408750, Guo Zhan Lum and co-workers propose a miniature soft robot, which can dispense four t-pes of drugs with reprogrammable drug-dispensing sequence and dosage. This soft robot can inspire unprecedented, targeted combination therap-, where multiple drugs must be delivered to various disease sites, each with a specific sequence and dosage of drugs.

Nature Medicine, Published online: 06 December 2024; doi:10.1038/s41591-024-03410-y

Nature Biomedical Engineering, Published online: 22 November 2024; doi:10.1038/s41551-024-01317-0

Nature Machine Intelligence, Published online: 14 November 2024; doi:10.1038/s42256-024-00914-7

3D metastructure absorbers offer lightweight, load-bearing electromagnetic absorption. This study presents a validated multi-scale model, highlighting the impact of unit geometry on field propagation, reflection loss, and the role of geometric symmetry in polarization insensitivity. These insights provide a foundation for designing next-generation broadband, wide-angle, polarization-insensitive absorbers with robust performance for practical applications.

Abstract

3D metastructure absorbers have gained attention for their lightweight, load-bearing capabilities, and superior electromagnetic wave absorption. However, the complex interplay between unit cell geometry, material properties, and electromagnetic response is not well understood, hindering the design of high-performance devices. A multi-scale model, validated is presented by simulations and experiments, that clarify the relationship between materials, structures, and electromagnetic behavior in 3D metastructures. By systematically investigating strut-based and sheet-based structures, volume fraction, unit size, crystal lattice orientation, and density gradient within TPMS-based unit cells, it is revealed that unit geometry significantly influences electromagnetic field propagation and reflection loss. Specifically, under the same unit size, sheet-based TPMS metastructures exhibit stronger reflectivity than strut-based ones, while multilayer structures show the opposite trend. The direct correlation is also further confirmed between geometric symmetry and polarization insensitivity, with orthogonal isotropic superstructures displaying excellent polarization-insensitive properties. This finding provides a new design principle for achieving robust, angle-independent absorption in these materials. This work enhances understanding of the structure-electromagnetic behavior interplay, guiding the design of next-generation broadband, wide-angle, and polarization-insensitive devices.

This work reports a novel single-material PSL process for the simultaneous fabrication of millimeter scale bifunctional devices with magnetic and locally conductive properties. Specially, stable magnetic GNs/resin composites are developed as the only printing material for bifunctional devices. This work presents a promising solution for the efficient and precise fabrication of bifunctional devices using single-material 3D printing technology.

Abstract

The development of projection-based stereolithography 3D printing techniques has provided a powerful approach to fabricate millimeter scale functional devices with complex structures. However, the current processes face challenges in frequent switching between multiple materials or processes, resulting in low efficiency and accuracy during the fabrication of bifunctional devices. To address these challenges, chemical deposition is utilized to modify graphene nanoplatelets (GNs) with Fe₃O₄ magnetic particles and incorporate them into the photosensitive resin, resulting in the development of a novel bifunctional printing material with magnetic and locally conductive properties. Furthermore, the localized conductivity of devices is controlled by an electric-field-assisted alignment process of the magnetic GNs (mGNs) during the printing process. Herein, this single-material projection-based stereolithography allows for the simultaneous fabrication of magnetic and locally conductive millimeter scale bifunctional devices without switching between multiple materials or processes. A magnetically driven circuit switch and signal coding gear are fabricated as demonstrations. This work significantly improves the efficiency and accuracy of fabricating millimeter scale bifunctional devices, thereby facilitating their application in the fabrication of miniaturized and integrated devices.

Inspired by the morphology and kinematics of carangiform fish, the negatively buoyant magnetic milliswimmer mimics fish muscle contractions, generating a carangiform-like body curvature, which results in similar swimming behavior and performance. Using magnetic torque to actuate its body, it can perform 3D free-swimming with enhanced controllability, maneuverability, and environmental adaptability.

Abstract

Miniature soft robots designed with magnetoelastic materials have the potential for noninvasive navigation in narrow spaces and innovative clinical therapies. However, the complex environment inside the body imposes stringent requirements on the motility and environmental adaptability of robots. Inspired by carangiform fish morphology and kinematics, a 3D free-swimming magnetic milliswimmer with enhanced controllability, maneuverability, and environmental adaptability is developed. This milliswimmer is negatively buoyant like most fishes and employs magnetic torque to actuate its body. It mimics fish muscle contractions and generates a carangiform-like body curvature distribution that results in comparable swimming behavior and performance. Compared with previous designs, it achieves over six times the equivalent motion performance and enables gravity-resisting free-swimming, with fish-like maneuverability (a minimum turning radius of just 0.05 body length and a maximum turning rate of up to 4737 deg s⁻¹). Its ability to transport and release cargo precisely while navigating three-dimensionally in an ex vivo porcine urinary system is demonstrated. The designed bionic magnetic soft robot is expected to advance biomedical applications of magnetoelastic materials, particularly in urinary and other clinical treatments.

Microscopic Structures in Living Tumor Characterized by Magnetic Nanoparticles

The article number 2404766 by Satoshi Ot and co-workers delves into the magnetic relaxation response of magnetic nanoparticles within tumors, unraveling insights into cancer cell distribution, stromal components, and vascularization. The intricate world of tumor microstructures is described by the combination of the non-biological samples. Measuring magnetic relaxation time and analyzing tumor structures paves the way for non-invasive cancer diagnostics and therapeutics using magnetic nanoparticles.

A novel formulation referred to water-stable magnetic lipiodol micro-droplets (MLMD) possesses properties such as flowability, shape adaptability, efficient drug loading, and compatibility with digital subtraction angiography (DSA) imaging is presented. On this basis, a close-looped magnetic navigation system featuring artificial intelligence (AI)-driven visual feedback for autonomous control has also been designed, to improve MLMD maneuverability in image-guided therapy.

Abstract

Magnetic microrobots, designed to navigate the complex environments of the human body, show promise for minimally invasive diagnosis and treatment. However, their clinical adoption faces hurdles such as biocompatibility, precise control, and intelligent tracking. Here a novel formulation (referred to water-stable magnetic lipiodol micro-droplets, MLMD), integrating clinically approved lipiodol, gelatin, and superparamagnetic iron oxide nanoparticles (SPION) with a fundamental understanding of the structure-property relationships is presented. This formulation demonstrates multiple improved properties including flowability, shape adaptability, efficient drug loading, and compatibility with digital subtraction angiography (DSA) imaging in both in vitro and in vivo experiments. This enables the MLMD as a versatile tool for image-guided therapy, supported by a close-looped magnetic navigation system featuring artificial intelligence (AI)-driven visual feedback for autonomous control. The system effectively performs navigational tasks, including pinpointing specific locations of MLMD, recognizing and avoiding obstacles, mapping and following predetermined paths, and utilizing magnetic fields for precise motion planning to achieve visual drug delivery. The MLMD combines magnetic actuation with an AI-directed close-looped navigation, offering a transformative platform for targeted therapeutic delivery.

In this article, a multifunctional component based on liquid metal is proposed installed in flexible robots. The component has variable stiffness, shape-aware, and heating capabilities. Herein, the final benefits of the three functions are maximized by optimizing the design parameters, which greatly expands the application scenarios of traditional flexible robots.

Conventional continuum robots have outstanding flexibility and dexterity. However, when the robot needs to interact with the environment, the softness may affect the performance of the robot. Especially in transport tasks, the softness of continuum robots can lead to handling failures and drastic drops in precision. The variable stiffness continuum robot combines the advantages of flexibility and rigidity, which is conducive to expanding the application scenarios of flexible continuum robots. This article proposes a flexible continuum robot that simultaneously realizes variable stiffness, shape-aware, and self-heating functions using liquid metal. The low-temperature phase transition property of liquid metal is utilized to realize the variable stiffness function; the overall stiffness of the robot can reach the range of 18.5–183 N m⁻¹, which can realize a tenfold stiffness gain. The conductivity of liquid metal is utilized to develop the shape-aware function, and the monitoring accuracy is within 5%. At the same time, this article utilizes the liquid metal's resistive thermal effect to realize heating function, so that the robot no longer needs heating systems such as heating wires and can realize the phase transition by energizing itself. Based on this design, the robot arm can realize the transition between maximum and minimum stiffness within 240 s.

A hybrid electromagnetic actuation system is developed to dynamically control the global and local magnetic field distributions, facilitating the precise manipulation of multiple microrobots with synchronized and differentiated motion profiles. This advanced technology offers significant advantages for applications such as non-contact particle manipulation, targeted drug delivery, and efficient micromixing, highlighting its potential for breakthroughs in biomedical and industrial fields.

Abstract

Magnetic microrobots are controlled to exhibit a wide range of motions, allowing them to navigate complex environments and perform multifunctional tasks with high precision. This work presents a novel hybrid electromagnetic actuation system by integrating two distinct conventional configurations, such as a paired-coils electromagnetic disc (EMD) system and a distributed electromagnetic array coil (EAC) system. In order to ensure the effective functioning of the microrobot, its motion dynamics are thoroughly analyzed to identify the critical kinetic parameters. For demonstration purposes, first, a mixing task is performed by employing a single microrobot actuated with simultaneous motions. The mixing efficiency is observed to reach 83% within 30 s, in contrast to the efficiency of control of 45%. Second, a structural reconfiguration function is demonstrated by employing an independent control of two U-shaped microrobots to form a new I-shaped microrobot. Last, differentiated motion control of multiple magnetic pads is demonstrated, resulting in various 2D static formations in the shapes of numbers and alphabets. The presented results hold great promise for advancing the field of microrobotics by offering a novel solution for versatile microrobot motion controls.

A miniature modular reconfigurable underwater robot system adopting the synthetic jet as a propulsion mechanism is developed. The motion module fuses two types of jet actuators and realizes the integration of power supply, control, and communication functions. Various configurations between different motion and intermediate modules are designed, and the application potential of the robot system is verified by experiments.

Abstract

Modular reconfigurable robots exhibit prominent advantages in the reconnaissance and exploration tasks within unstructured environments for their characteristics of high adaptability and high robustness. However, due to the limitations in locomotion mechanism and integration requirements, the modular design of miniature robots in the aquatic environment encounters significant challenges. Here, a modular strategy based on the synthetic jet principle is proposed, and a modular reconfigurable robot system is developed. Specialized bottom and side jet actuators are designed with vibration motors as excitation sources, and a motion module is developed incorporating the jet actuators to realize three-dimensional agile motion. Its linear, rotational, and ascending motion speeds reach 70.7 mm s⁻¹, 3.3 rad s⁻¹, and 28.7 mm s⁻¹, respectively. The module integrates the power supply, communication, and control system with a small size of 48 mm × 38 mm × 38 mm, which ensures a wireless controllable motion. Then, various configurations of the multi-module robot system are established with corresponding motion schemes, and the experiments with replaceable intermediate modules are further conducted to verify the transportation and image-capturing functions. This work demonstrates the effectiveness of synthetic jet propulsion for aquatic modular reconfigurable robot systems, and it exhibits profound potential in future underwater applications.

Modular Fabrication of GFET Biosensors

In article number 2401796, Zhen Zhao, Jiahong Wang, Wenhua Zhou, and co-workers present a simple and robust graphene field-effect transistor biosensor fabricated through modular techniques, enabling a high-sensitive and specific detection of nucleic acids. This strategy also offers a possibility of adapting various microfluidic electronic devices with complex architectures for customized applications.