Significance: For decades, the propulsion of sperms has been traditionally attributed to the beating or rotating of the soft tails. However, this work disclosed an unusual swimming model of Ray sperms whose propulsion is from not only the helical tail but also the unique spiral head (i.e., the head can contribute ∼31% of the force in propulsion). Such a propulsion mechanism provides Ray sperms with high adaptability to large environmental viscosities along with advantages in linearity, straightness, and efficiency. This study expands our knowledge on the microorganisms’ motion and provides inspirations for engineering design.

Tethered-satellite systems have great potential in completing various space missions. However, existing researches mainly focus on the deployment of satellites in a circular orbit, whereas deployment in an elliptical orbit, especially with disturbances, is rarely studied. This study develops a new control strategy to deploy tethered satellites in a low-eccentricity elliptical orbit that also considers system uncertainties and external disturbances. First, the periodical solution of the librational motion of a tethered-satellite system in an elliptic orbit is calculated. Because there is no fixed equilibrium point for deployment in elliptical orbits, the periodical solution is set as the end condition for deployment. After that, the controllability of the system is verified and an open-loop tension-control law is optimized by particle swarm optimization (PSO) and the Nelder-Mead method. To eliminate effects from uncertainties in initial states and errors from the deployment mechanism, an adaptive sliding mode controller is designed to achieve high-precision trajectory tracking. The performance of the proposed controller is compared quantitatively with a proportion-derivative (PD) controller and normal sliding mode controller. Furthermore, Monte Carlo simulations are conducted to demonstrate the effectiveness and robustness of the proposed controller when subjected to uncertain initial states. The simulation results indicate that the proposed control strategy enables the stable deployment of tethered-satellite systems despite the uncertainties and perturbations.

The helical microstructure has been widely applied to various industries, including the mechanical manufacture, electronics, and biomedical engineering. Due to the miniature size of the helical microstructure, the low manufacture precision will highly degrade its working performance. Although current manufacture methods can realize its fabrication with relatively high accuracy, the used material is constrained to several specific conditions. To address the above problems, this paper proposes a laconic and high-precision 3D manufacture method for the helical microstructure based on the micro robotic system without the limitation of materials. In this work, the micro robotic system with 6 degrees-of-freedom (DOFs) is developed for manufacture. Then the image processing operation for providing feedback information is introduced. Thirdly, the trajectory of each individual robotic module is designed according to the structure's certain size. After that, the control system with feedforward and double feedback is reported to realize the accurate manufacture. Finally, the experimental results demonstrate that the manufacture precision can reach up to 2 micro meters with the standard deviation (STD) of 1.06. This research will pave a new path for the high-precision 3D manufacturing at small scale, and have long-term impacts on robot-aided manufacturing system with high potential for commercialization in the future.

The helical microstructure has been regarded as one of the essential geometrical shapes widely utilized in microelectromechanical systems (MEMS) and lab on chip systems. Different manufacture methods for helical microstructures attracted the researchers' attention due to their respective advantages. Inspired by traditional machining techniques, this paper reports a new manufacture method for accurate three dimensional (3D) helical microstructures based on in-situ scanning electron microscope (SEM) nanorobotic manipulation system. Compared with existing manufacture techniques, our proposed method is laconic, precise and material unconstrained. Besides, in-situ force and electric measurement can be realized immediately after the helical microstructure being manufactured. In this work, the system with three degree-of-freedoms (DOFs) nanorobotic manipulator integrated inside SEM is firstly introduced. Secondly, the 3D manufacture method with proportional integral derivative (PID) control is proposed to fabricate the desired helical microstructures. After that, the helical microstructures are manufactured and the manufacturing accuracy is analyzed. The manufacturing accuracy can be controlled within 10 micrometers. Finally, the force and electric demarcation of the fabricated helical microstructure is conducted to excavate the potential adhibition in in-situ SEM force and electric measurement, components for MEMS and lab on chip systems, etc. This research opens new prospects for the precise in-situ 3D manufacture of helical microstructures via the nanorobotic system, which is expected to give a long-term impact on MEMS, lab on chip systems, telecommunications, and so on.

The microwaveguide coupling is a critical process to manufacture precise optical elements and optical devices, which are widely used for sensing. During the coupling process, the microwaveguides should be matched well to ensure the amount of light as much as possible. However, the used light will inevitably disturb the recognition of position when using the machine vision technology. Even the microwaveguides can be aligned well based on the position, the amount of light may still fail to be maximum due to the fabrication error. Hence, achieving accurate and efficient alignment of microwaveguides remains unreachable in previous works. To tackle the above challenges, we present a robotic micro-positioning system as well as the corresponding control strategy based on a hybrid position and light intensity feedback. In this work, a microrobotic positioning system with 3 degrees of freedom (DOFs) is firstly developed and integrated with an optical microscopy. Then the optimal trajectory for coupling including obstacle avoidance is designed. After that, a model-free adaptive controller (MFAC) is proposed to guarantee the tracking precision. Lastly, simulation and experimental results demonstrate that the proposed system can achieve the coupling of the microwaveguides with 300.41% sensitivity improvement over the traditional method with single position feedback. This work provides a general solution to the assembly problem for the optical devices, and will have a long term positive impact on the micro manufacture filed.

Precise specimen's installation is a sticking point to ensure the characterization accuracy of the in-situ material property test. Although it is common knowledge that specimen's plane misaligned installation (PMI) would cause extra force loading during mechanical testing, there are few effective solutions available to deal with it at the current stage, especially during the in-situ scanning electron microscopy (SEM) test. Taking into consideration the charge fluctuation phenomenon under SEM, this paper proposes a highlight area variation (HAV) method for specimen deformation judgment, i.e., the specimen deformation is defined when the highlight area changes greater than 20% of the initial value of the specimen surface. Three types of specimens with different resistivities, i.e., human hair (electrical resistivity ∼3 × 10¹² Ω cm), optical fiber (electrical resistivity ∼10¹⁷ Ω cm), and magnetic wire (electrical resistivity ∼2 × 10⁻⁵ Ω cm), are chosen to verify the effectiveness of the HAV method. Furthermore, combined with the developed robot-aided alignment system, the specimen's PMI problem can also be solved. In the demonstration, the human hair specimen is installed across two specimen stages and its in-situ twisting (in 360°) test is implemented. The results clearly indicate that the HAV method and the robot-aided alignment system are practical and reliable, and the specimen can be aligned on the same plane and installed precisely with accuracy up to 3 μm. This method will benefit the in-situ SEM material mechanical property test and has a significant impact in fundamental material research.