We develop biohybrid magnetic microrobots by electrostatic self-assembly of nonmotile sperm cells and magnetic nanoparticles. Incorporating a biological entity into microrobots entails many functional advantages beyond shape templating, such as the facile uptake of chemotherapeutic agents to achieve targeted drug delivery. We present a single-step electrostatic self-assembly technique to fabricate IRONSperms, soft magnetic microswimmers that emulate the motion of motile sperm cells. Our experiments and theoretical predictions show that the swimming speed of IRONSperms exceeds 0.2 body length/s (6.8 ± 4.1 µm/s) at an actuation frequency of 8 Hz and precision angle of 45°. We demonstrate that the nanoparticle coating increases the acoustic impedance of the sperm cells and enables localization of clusters of IRONSperm using ultrasound feedback. We also confirm the biocompatibility and drug loading ability of these microrobots, and their promise as biocompatible, controllable, and detectable biohybrid tools for in vivo targeted therapy.

Positioning conventional endovascular catheters is not without risk, and there is a multitude of complications that are associated with their use in manual surgical interventions. By utilizing surgical manipulators, the efficacy of remote-controlled catheters can be investigated in vivo. However, technical challenges, such as the duration of catheterizations, accurate positioning at target sites, and consistent imaging of these catheters using nonhazardous modalities, still exist. In this paper, we propose the integration of multiple sub-systems in order to extend the clinical feasibility of an autonomous surgical system designed to address these challenges. The system handles the full synchronization of co-operating manipulators that both actuate a clinical tool. The experiments within this study are conducted within a clinicallyrelevant workspace and inside a gelatinous phantom that represents a life-size human torso. A catheter is positioned using magnetic actuation and proportional-integral (PI) control in conjunction with real-time ultrasound images. Our results indicate an average error between the tracked catheter tip and target positions of 2.09 ± 0.49 mm. The median procedure time to reach targets is 32.6 s. We expect that our system will provide a step towards collaborative manipulators employing mobile electromagnets, and possibly improve autonomous catheterization procedures within endovascular surgeries.

The development of magnetically powered microswimmers that mimic the swimming mechanisms of microorganisms is important for lab‐on‐a‐chip devices, robotics, and next‐generation minimally invasive surgical interventions. Governed by their design, most previously described untethered swimmers can be maneuvered only by varying the direction of applied rotational magnetic fields. This constraint makes even state‐of‐the‐art swimmers incapable of reversing their direction of motion without a prior change in the direction of field rotation, which limits their autonomy and ability to adapt to their environments. Also, due to constant magnetization profiles, swarms of magnetic swimmers respond in the same manner, which limits multiagent control only to parallel formations. Herein, a new class of microswimmers are presented which are capable of reversing their direction of swimming without requiring a reversal in direction of field rotation. These swimmers exploit heterogeneity in their design and composition to exhibit reversible bidirectional motion determined by the field precession angle. Thus, the precession angle is used as an independent control input for bidirectional swimming. Design variability is explored in the systematic study of two swimmer designs with different constructions. Two different precession angles are observed for motion reversal, which is exploited to demonstrate independent control of the two swimmer designs.

Parallel mechanisms have been investigated during the last two decades, due to the fact that they present some advantages in a comparison with serial structures. This work deals with the error analysis of a 3-dof asymmetric parallel mechanism, purposely conceived for milling applications. In a comparison with the previous proposed concepts, this type of kinematic structure demonstrates a promising behavior. Topologically, the architecture is simpler and lighter than Tricept because it has no central passive limb. In addition, only the constraining active limb needs to satisfy the parallelism and orthogonality conditions. Furthermore, one degree of freedom, associated to the third actuator, is decoupled from the other two. Important issues, related to this type of kinematic structure, such as the mappings of the tool positioning error throughout the available workspace, due to the actuators imprecisions and manufacturing tolerances, are discussed in detail.

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