Magnetic micromachines can be delivered into the body and then controlled externally using a magnetic field. Such micromachines could be used to deliver a therapeutic agent to a specific location in a minimally invasive manner or control adaptive implants. However, in many cases multiple micromachines may be required. For example, a ‘swarm’ of micromachines could perform advanced medical interventions, such as effectively delivering chemotherapeutic drugs throughout the complex architecture of a solid tumor.
Precisely controlling such a swarm in the body is a serious challenge. Controlling each micromachine in a swarm individually is important to perform complex tasks in the body. However, applying a uniform magnetic stimulus to the whole swarm and hoping for the best does not facilitate individual control of each microrobot. Making individual robots perform specific tasks is not possible using a one-size-fits-all stimulus.
The challenge lies in limiting a magnetic field to a highly specific area to control only the micromachines within that area. Researchers with Phillips in Hamburg, Germany have recently published a study in Science Robotics demonstrating a clever arrangement of magnetic fields that can selectively control individual microrobots that are identical to each other and are in really close proximity. These microrobots require no internal power source or method of propulsion and are completely powered and controlled using the magnetic fields.
The device that generates the magnetic fields has a focal point containing a very low magnetic field gradient. This means that every microrobot outside of the focal point can be “locked” in place, while the “unlocked” microrobot in the focal point can be controlled by another magnetic field. The focal point can be moved about, meaning that different machines can be locked and unlocked and controlled individually.
In the video below, the researchers demonstrate the technique by screwing and unscrewing individual screws in close proximity. So far, the technique can manipulate individual components as close as 3–4 mm in distance from each other.