Untethered miniature robots that can access narrow and harsh environments in the body show great potential for future biomedical applications. Despite the many types of millirobot that have been developed, swimming against the fast blood flow remains a big challenge due to lack of the ability to stay still and the large fluidic resistance from blood. This article proposes an on-wall-rotating strategy and a streamlined millirobot to achieve effective upstream motion in the lumen. First, the principle of on-wall-rotating strategy and the dynamic motion model of the millirobot is established. Then, a critical safety angle$\theta _{s}$is theoretically and experimentally analyzed for the safe and stable control of the robot. After that, a series of experiments are conducted to verify the proposed driving strategy. The results suggest that the robot is able to move at a speed of 5 mm/s against flow velocity of 138 mm/s, which is comparable to the blood flow of 2700 mm$^{3}$/s and several times faster than other reported driving strategies. This work offers a new strategy for the untethered magnetic robot construction and control for blood vessels, which would promote the application of millirobot for biomedical engineering.

In the context of robotic high-precision soldering, we propose an image-based pin alignment control method based on active plastic deformation. The plastic deformation is a well-known failure mechanism in most situations, which includes a phenomenon that the objects do not return original state. Here, in contrast to this convention, we utilize the plastic deformation of the metal pin to do pin alignment for improving the quality of the solder joint. To address this, we embed the springback compensation into the image-based pin alignment controller. Lastly, the proposed strategy is successfully demonstrated and evaluated in a practical modified robotic manipulation system. The result shows that the alignment error is less than 20µm, which is far less than pin alignment without considering plastic deformation and elastic recovery. This work considers active plastic deformation and spontaneous elastic recovery of soft object, which would greatly promote the use of robotics in micromanufacturing and microfabrication in lad and industry, especially for soft objects.

High flexible and high precise manipulation is one of the most critical technique for complex microsystem’s measurement, manufacture, and assembly. Although recent advances in microrobotics have successfully realized the automatic manipulation and positioning of tiny objects, their flexible manipulation in 3-D free space remains a challenge, such as the wide-angle rotation manipulation of microsize sphere, due to the complicate surface forces. Herein, this article proposed a feedforward model and realized the precise rotation for microsized sphere by two cooperative flexible micropipettes. Firstly, a microrobotic manipulation system with six degrees-of-freedom (DOFs) was developed and integrated with the microscope. Then, a feedforward compensation control strategy involving dual rotation was proposed for the precise manipulation of microsized sphere (${\sim }90~\mu \text {m}$) based on the analysis of contact forces. As a result, the rotation of the microsized sphere in two different planes was realized and the microsized sphere release procedure was also accomplished after rotation. Compared with existing techniques only allowing limited amplitudes rotation, this article realizes wide-angle rotation manipulation of microsized sphere in 3-D free space. This research opens new prospects for the microsized object accurate manipulation, which is expected to give a long-term impact for complex microsystem’s manufacture and assembly.Note to Practitioners—This article is motivated by the problem of the flexible manipulation of tiny object in 3-D space. The proposed nanorobotic manipulation system, two micropipettes and feedforward compensation model control strategy could realize the precise translational and rotational manipulation of microbeads in 3-D space, which offers obvious advantages of existing techniques. The proposed system and method could be a general solution for precise and flexible micromanipulation. Thus, it could find wide applications ranging from fundamental research to industrial applications, such as biological cell positioning, characterization of a particular micro/nanoregion, microassembly, and manufacturing.