Remotely controlled soft continuum robots with active steering capability have broad prospects in medical applications. However, conventional continuum robots have the miniaturization challenge. This paper presents a microscale soft continuum microrobot with steering and locomotion capabilities based on magnetic field actuation. The magnetically driven soft continuum microrobot is made of NdFeB particles and polydimethylsiloxane (PDMS), and it can be as small as 200 μ m in diameter. Moreover, a hydrogel layer is covered on the surface of the microrobot, which not only overcomes the adhesion force between the microobjects and the soft tip but also reduces the friction between the microrobot and substrate. The performance test indicates the soft continuum microrobot featured excellent control and steering capabilities. The experimental results demonstrate that the soft continuum microrobot can travel through the microfluidic channel by its own vibration and flexibly steer in a bifurcation environment. Moreover, the micromanipulation of microbeads in the microfluidic channels proves that the proposed microscale soft continuum microrobot has a great potential for intravascular manipulation.

Cell stiffness is an essential label-free biomarker used to diagnose and sort cells at the single-cell level. Here, we integrated magnetic tweezers on an efficient cell arraying microfluidic device to evaluate the mechanical properties of single cells. Two motion modes under pulsed electromagnetic fields have been proposed for magnetic beads. They were magnetically actuated to approach the measuring cells at a distance in rotation mode and move experimentally with the maximal velocity of 23 μm s ^-1 under a rotating magnetic field of 45 Hz and 45 mT. In contrast, the magnetic beads were driven at close range in translation mode to approach and apply extrusion pressure on the target cells under a locally constant magnetic field gradient. The simulation results of the fluid field caused by the moving bead revealed the difference distribution in velocity and pressure under two motion modes, proving the rationality of the motion mode setting. Experimentally, Hela cells and C2C12 cells arrayed in the microfluidic device were physically squeezed by magnetic tweezers, and cell stiffness was measured. Compared to the measurement results with AFM, the proposed method used to measure Young's modulus of the cells was thought to be dependable. We envision the proposed on-chip platform integrated with the magnetic tweezer could show a potential application for the efficient and flexible measurement of biomechanical properties in the future.

Magnetic microrobots are vital tools for targeted therapy, drug delivery, and micromanipulation on cells in the biomedical field. In this paper, we report an automated control and path planning method of magnetic microrobots based on computer vision. Spherical microrobots can be driven in the rotating magnetic field generated by electromagnetic coils. Under microscopic visual navigation, robust target tracking is achieved using PID–based closed–loop control combined with the Kalman filter, and intelligent obstacle avoidance control can be achieved based on the dynamic window algorithm (DWA) implementation strategy. To improve the performance of magnetic microrobots in trajectory tracking and movement in complicated environments, the magnetic microrobot motion in the flow field at different velocities and different distribution obstacles was investigated. The experimental results showed that the vision-based controller had an excellent performance in a complex environment and that magnetic microrobots could be controlled to move to the target position smoothly and accurately. We envision that the proposed method is a promising opportunity for targeted drug delivery in biological research.

Zebrafish embryo injection is often required in biomedical research using zebrafish. In the injecting operation, trapping and rotating the zebrafish embryo to achieve a proper posture is essential for the high success rate. We proposed an on-chip platform capable of efficient and automatic trapping and rotating for the injection of zebrafish embryos. A low-cost 3D-printed microchannel is designed to trap zebrafish embryos into the cavity array. The blind-hole design at each cavity can generate microbubbles, and the bubbles exposed to the acoustic wave with a specific frequency can trap and rotate the zebrafish embryos. The progress, including trapping and rotating, can be monitored and executed automatically with computer vision assistance. Experimental results show that we realized on-chip trapping and rotating operations successfully. The success rate of trapping zebrafish embryos was up to 99%, and the time of trapping a single embryo was as low as 0.2 s. Embryo rotation could be achieved by two different modes, including continuous rotation and intermittent rotation. The accuracy and maximal velocity of rotating the embryo reached 5° and 3.5 r/s, respectively. Thus, we believe the proposed efficient automatic on-chip trapping and rotating platform could support the zebrafish embryo injection well.

In the last two decades, the micromanipulation technique has been widely utilized in industrial and biological fields. However, existing micromanipulation methods can hardly meet all the demands in both fields. In this article, we present an all-purpose magnetically driven micromanipulation system with designed contact and noncontact modes for numerous industrial and biological applications, respectively. In the system, a micropipette containing the ferromagnetic beads driven by themagnetic field presentshigh-precision and high-speed motions. With another micropipette, this two-finger microhand can efficiently perform the chopstick-like grasp motion by physical contact. The vibration-based active release relying on the high-speed motion can help release the targets adhering to the end-effector. Besides, local whirling flow surrounding the micropipette induced by high-speed circular motion can trap, transport, and rotate microtargets without contact like a hydrodynamic tweezer to operate micro bio-targets without any damages. In experiments, microbeads are grasped and releasedefficiently in the desired positions using the chopstick-like two-finger microhand mode, and the arrays of a hexagon and “TMECH” have been assembled. The hydrodynamic tweezer mode is adopted to trap, transport, and rotate the microbeads and further applied in the operations of the mouse egg cells. We believe the proposed magnetic micromanipulation system, as an all-purpose tool at the microscale, holds great potential in industrial and biological applications.

In recent years, micromanipulators have provided the ability to interact with micro-objects in industrial and biomedical fields. However, traditional manipulators still encounter challenges in gaining the force feedback at the micro-scale. In this paper, we present a micronewton force-controlled two-finger microhand with a soft magnetic end-effector for stable grasping. In this system, a homemade electromagnet was used as the driving device to execute micro-objects manipulation. There were two soft end-effectors with diameters of 300 μm. One was a fixed end-effector that was only made of hydrogel, and the other one was a magnetic end-effector that contained a uniform mixture of polydimethylsiloxane (PDMS) and paramagnetic particles. The magnetic force on the soft magnetic end-effector was calibrated using an atomic force microscopy (AFM) probe. The performance tests demonstrated that the magnetically driven soft microhand had a grasping range of 0–260 μm, which allowed a clamping force with a resolution of 0.48 μN. The stable grasping capability of the magnetically driven soft microhand was validated by grasping different sized microbeads, transport under different velocities, and assembly of microbeads. The proposed system enables force-controlled manipulation, and we believe it has great potential in biological and industrial micromanipulation.