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Magnetically powered microswimmers exhibit various advantages in practical applications, including simplified propulsion mechanism of nonreciprocal motion in a low Reynolds (Re) number environment, high flexibility, and high efficiency. Inspired by the morphological and dynamic analyses of microscale nonreciprocal locomotion, this study characterizes the properties of torque-driven segmented microswimmers that actuated by an external oscillating magnetic field. The proposed microswimmer includes a magnetized head and several non-magnetized rigid body segments fabricated by two-photon lithography. The components of the microswimmer are linked together by rigid mechanical joints with an angle limiting mechanism, thereby forming simplified and discrete wave locomotion in a low Reynolds number environment. The motion of this multi-segment structure with different segment number is analyzed, and swimming locomotion involving segment interaction of the microswimmers and ambient liquid is characterized. Theoretical and experimental studies indicate that a minimum of three segments are needed to enable the microswimmers to move forward, whereas having four segments exhibits the best comprehensive performance. Based on this analysis, the geometric parameters of the four-segment microswimmers are further optimized, and experiments verify the enhancement of its motion capacity in a low Re number regime. INDEX TERMS magnetic microrobot; microswimmer; multi-segment structure.

Laser beam steering has been widely studied for the automation of surgery. Currently, flexible instruments for laser surgery are operated entirely by surgeons, which keeps the automation of endoluminal surgery at the initial level. This paper introduces the design of a new workflow that enables the task autonomy of laser-assisted surgery in constrained environments such as the gastrointestinal (GI) tract with a flexible continuum robotic system. Unlike current, laser steering systems driven by piezoelectric require the use of high voltage and are risky. This paper describes a tendon-driven 2 mm diameter flexible manipulator integrated with an endoscope to steer the laser beam. By separating its motion from the total endoscopic system, the designed flexible manipulator can automatically manipulate the laser beam. After the surgical site is searched by the surgeon with a master/slave control, a population-based model-free control method is applied for the flexible manipulator to achieve accurate laser beam steering while overcoming the noise from the visual feedback and disturbances from environment during operation. Simulations and experiments are performed with the system and control methods to demonstrate the proposed framework in a simulated constrained environment.

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