Distributed magnetic control strategies for small-scale Robots

Wireless manipulation of small-scale objects is highly attractive and crucial in many fields, especially in the biomedical. Several actuation modalities exist, including optical, ultrasonic, chemical, etc. Among those, magnetic actuation has become paramount for its precision in control and minimal invasiveness, enabling it to operate in constrained environments. Furthermore, the magnetic field interactions with the human body are harmless and safe because the human body is transparent to them. Magnetic actuation refers to the application of magnetic forces or torques to control the movement and behavior of magnetized objects. The review of the current literature revealed that most existing solutions rely on global, external stationary magnets to generate magnetic fields across the body to control magnetic objects inside it, often requiring substantial power consumption. Due to the rapid decrease in magnetic field intensity with distance, the generated field must be significantly stronger than what is required at the target location. In contrast, only a limited number of studies have explored a localized approach that leverages miniaturized magnetic field sources, placed inside the body, for direct in situ control within a defined workspace. Such approaches demonstrated highly promising results. Nevertheless, all these local control studies use constrained workspaces, without the possibility to move the system from one place to another and with the need to introduce inside the body, not only the coils, but also the real boundaries for the magnetic object. The objective of this research was to design, numerically model, fabricate, and experimentally validate a real-time electromagnetic control strategy aimed at the localized manipulation of magnetic objects within an unconstrained 2D workspace, eliminating the need for physical boundaries. In total, two predefined trajectories were tested to guide magnetic spheres of varying diameters using configurations of 2 and 3 electromagnetic coils. The study explored different combinations of sphere size, surface properties, and surrounding media to understand how these factors influence the magnetic control of objects. By systematically varying these parameters, the research aimed to optimize control precision and reliability, as well as to identify the key factors that need to be considered when designing magnetic actuation systems for specific biomedical applications. Understanding these interactions is crucial for enhancing the accuracy and responsiveness of the system, particularly when operating in diverse and complex environments. Additionally, rectangular and circular workspaces were used with a controllable dimension of up to 4.5 cm. The implementation of virtual boundaries and workspace definitions led to the development of an innovative local control strategy, enabling precise manipulation of magnetic objects without the need to confine them within a predefined physical boundary.