Bo Hao

Abstract Magnetic miniature soft‐bodied robots allow non‐invasive access to restricted spaces and provide ideal solutions for minimally invasive surgery, micromanipulation, and targeted drug delivery. However, the existing elastomer‐based (silicone) and fluid‐based (ferrofluid or liquid metal) magnetically actuated miniature soft robots have limitations. Owing to its limited deformability, the elastomer‐based small‐scale soft robot cannot navigate through a highly restricted environment. In contrast, although fluid‐based soft robots are more capable of deformation, they are also limited by the unstable shape of the fluid itself, and are therefore poorly adapted to the environment. In this study, non‐Newtonian fluid‐based magnetically actuated slime robots with both the adaptability of elastomer‐based robots and reconfigurable significant deformation capabilities of fluid‐based robots are demonstrated. The robots can negotiate through narrow channels with a diameter of 1.5 mm and maneuver on multiple substrates in complex environments. The proposed slime robot implements various functions, including grasping solid objects, swallowing and transporting harmful things, human motion monitoring, and circuit switching and repair. This study proposes the design of novel soft‐bodied robots and enhances their future applications in biomedical, electronic, and other fields.

Miniature magnetic soft machines could significantly impact minimally invasive robotics and biomedical applications. However, most soft machines are limited to solid magnetic materials, whereas further progress also relies on fluidic constructs obtained by reconfiguring liquid magnetic materials, such as ferrofluid. Here we show how harnessing the wettability of ferrofluids allows for controlled reconfigurability and the ability to create versatile soft machines. The ferrofluid droplet exhibits multimodal motions, and a single droplet can be controlled to split into multiple sub-droplets and then re-fuse back on demand. The soft droplet machine can negotiate changing terrains in unstructured environments. In addition, the ferrofluid droplets can be configured as a liquid capsule, enabling cargo delivery; a wireless omnidirectional liquid cilia matrix capable of pumping biofluids; and a wireless liquid skin, allowing multiple types of miniature soft machine construction. This work improves small magnetic soft machines' achievable complexity and boosts their future biomedical applications capabilities.

Electrical stimulation is a promising method to modulate gastrointestinal disorders. However, conventional stimulators need invasive implantation and removal surgeries associated with risks of infection and secondary injuries. Here, we report a battery-free and deformable electronic esophageal stent for wireless stimulation of the lower esophageal sphincter in a noninvasive fashion. The stent consists of an elastic receiver antenna infilled with liquid metal (eutectic gallium-indium), a superelastic nitinol stent skeleton, and a stretchable pulse generator that jointly enables 150% axial elongation and 50% radial compression for transoral delivery through the narrow esophagus. The compliant stent adaptive to the dynamic environment of the esophagus can wirelessly harvest energy through deep tissue. Continuous electrical stimulations delivered by the stent in vivo using pig models significantly increase the pressure of the lower esophageal sphincter. The electronic stent provides a noninvasive platform for bioelectronic therapies in the gastrointestinal tract without the need for open surgery.

A novel piezoelectric-actuated rail-type mobile platform is proposed in this article, which has potential application in the inspection and maintenance tasks of the Tokamak vacuum vessel as it holds good environmental adaptability to extreme environments, such as strong magnetic fields, high vacuum, and high temperature. The rail-type piezoelectric-actuated mobile platform consists of a rail and a framed piezoelectric actuator operating with two orthogonal bending vibrations. The framed piezoelectric actuator moves on the rail by friction. At first, a semianalytical model is created for the framed piezoelectric actuator utilizing the transfer matrix method in order to reveal its dynamic behavior. Then, the prototype of the proposed framed piezoelectric actuator is manufactured and assembled, and its vibration characteristics are measured to verify the feasibility of the developed transfer matrix model. Additionally, the mechanical output performances of the rail-type mobile platform prototype are investigated experimentally, and it is observed that the maximum speed of the mobile platform prototype reached 384.68 mm/s when the amplitude of the driving voltage is 400 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> , its maximum load-weight to self-weight ratio reached 7.6 when the excitation voltage is 300 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> , its maximum output force is about 1.8 N under the excitation voltage of 400 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> , and the minimum displacement resolution is 4 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m when operated in the stepping mode. Finally, the extreme environment (temperature: 0–120 °C and vacuum: 3×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> –10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> Pa) tests are carried out to measure the output performances of the mobile platform prototype. The results show that the platform prototype is capable of carrying loads in a high-temperature and high-vacuum environment.

Untethered miniature soft robots have significant application potentials in biomedical and industrial fields due to their space accessibility and safe human interaction. However, the lack of selective and forceful actuation is still challenging in revolutionizing and unleashing their versatility. Here, we propose a focused ultrasound-controlled phase transition strategy for achieving millimeter-level spatially selective actuation and Newton-level force of soft robots, which harnesses ultrasound-induced heating to trigger the phase transition inside the robot, enabling powerful actuation through inflation. The millimeter-level spatial resolution empowers single robot to perform multiple tasks according to specific requirements. As a concept-of-demonstration, we designed soft robot for liquid cargo delivery and biopsy robot for tissue acquisition and patching. Additionally, an autonomous control system is integrated with ultrasound imaging to enable automatic acoustic field alignment and control. The proposed method advances the spatiotemporal response capability of untethered miniature soft robots, holding promise for broadening their versatility and adaptability.