The magnetically actuated robot has valuable potential in biomedicine, bioengineering, and biophysics for its capability to precisely manipulate particles or biological tissues. However, the deformability of rigid robots with predetermined shapes is limited, which constricts their functions and causes inconvenience for robots' movement in constricted space. In this study, we proposed a feasible and efficient ferrofluid-based robot for the transportation of tiny particles and blocks. In addition, a method to generate a patterned magnetic field is also introduced to model a ferrofluid-based robot with an adaptive shape. Benefiting from the paramagnetism and fluidity of the ferrofluid-based robot, it also demonstrates outstanding motion accuracy and output force on a superhydrophobic surface. Because of its excellent motion characteristics, high motion accuracy, and high measured output force, the proposed ferrofluid-based robot has great advantages in the field of microoperation. The correlation coefficient between the motion trajectory of the ferrofluid-based robot and the motion trajectory of the micro-stages is 0.9967. The position error is less than 1.5% of the total stroke.

Non-contact manipulation technology has a wide range of applications in the manipulation and fabrication of micro/nanomaterials. However, the manipulation devices are often complex, operated only by professionals, and limited by a single manipulation function. Here, we propose a simple versatile optoelectronic tweezer (OET) system that can be easily controlled for manipulating microparticles with different sizes. In this work, we designed and established an optoelectronic tweezer manipulation system. The OET system could be used to manipulate particles with a wide range of sizes from 2 μm to 150 μm. The system could also manipulate micro-objects of different dimensions like 1D spherical polystyrene microspheres, 2D rod-shaped euglena gracilis, and 3D spiral microspirulina. Optical microscopic patterns for trapping, storing, parallel transporting, and patterning microparticles were designed for versatile manipulation. The sorting, rotation, and assembly of single particles in a given region were experimentally demonstrated. In addition, temperatures measured under different objective lenses indicate that the system does not generate excessive heat to damage bioparticles. The non-contact versatile manipulation reduces operating process and contamination. In future work, the simple optoelectronic tweezers system can be used to control non-contaminated cell interaction and micro-nano manipulation.

Flexible magnetic small‐scale robots (overall dimensions smaller than 1 cm) can use a patterned magnetization profile to noninvasively access a confined, enclosed liquid environment and therefore achieve applications in object manipulation or in minimally invasive procedures. Existing magnetic‐controlled small‐scale robots have shown wide usage for their high mobility and higher degrees of freedom than their rigid counterparts. Herein, an octopus‐like soft robot is proposed for potential use in biomedical and engineering fields. First, a magnetic control system is established, which uses the minimum number of coils arranged by a regular tetrahedron structure. This system responds quickly and with high precision to propel a robot in 3D space utilizing the coupled field from multiple electromagnets in concert. An octopus‐like robot with three legs is designed, which moves freely in the workspace without constraints. A time‐asymmetric gradient magnetic field is applied, to ensure that the movement of the robot is more stable and controlled. At the same time, the movement of the tail improves the precision of the robot and makes control easier.

Magnetic soft robots have the potential to directly access areas of the human body that are currently inaccessible or difficult to reach for minimally invasive medical operations or drug delivery. Recently, ferrofluids containing magnetic nanoparticles with unique deformation properties have been extensively investigated. In this study, a ferrofluid robot for targeted drug delivery is proposed, while the control of ferrofluid robots is implemented in a 3D vascular model. Four-solenoid control systems with visual feedback are designed to achieve said implementation. Through numerical simulation and actual measurement, the magnetic field gradient generated by the system can reach 4.14 T/m, and three-dimensional control of ferrofluid robots can be realized. The deformation ability of ferrofluid robots is investigated, and the ferrofluid robots are found to pass through slits four times smaller than the diameter of the ferrofluid robots. Also, the deformation of the ferrofluid robots can reduce the drag force in the flow field by 43.75% through finite element simulation. The maximum control error does not exceed 0.3 mm. Finally, the coil system controls a ferrofluid droplet to achieve autonomous motion in a 3D vascular model with a maximum internal diameter of 3 mm. The implementation of the control effect allows for the technical potential of ferrofluid robots in drug delivery through vascular navigation.

Liquid transport regulation has attracted wide attention recently due to its potential applications in micro-fluidic devices, heat management, and mechanical engineering. Various liquid regulation strategies for direction guiding and speed enhancing have been developed with inspirations from nature, such as desert beetles and Nepenthes alata peristome with either gradient wettability or anisotropic structures, whereas their combined strategies for enhanced liquid regulations have barely been discussed due to the unclear coupling mechanisms. Herein, inspired by liquid transporting structure on Ligia exotica's leg, a smart flexible surface with gradient distributed and magnetized micro-cilia array is proposed to realize liquid spreading regulations in speed and direction. Different gradients and magnetic fields have been compared for liquid regulating performances, where the anisotropy ratio of liquid spreading could be enhanced from 0 on uniform surface to ∼0.3 on gradients surface, to even ∼0.6 by coupling magnetic field. The underlying liquid regulating mechanism has been established based on the mutual effects of liquid pinning and capillarity at different cilium inclined angles, cilium gap distance, and surface wettability. Finally, several liquid regulation applications are explored and offer potentials for fields of medicine and heat management.

Magnetically Actuated Millirobots