Using an electric field, researchers can control how microswimmers move. A team from the Max Planck Institute for Dynamics and Self-Organization (MPI-DS), the Indian Institute of Technology (IIT) Hyderabad, and the University of Twente in the Netherlands have described the physical principles behind this by comparing their findings from experiments with predictions from theoretical models. They can adjust the direction and manner of motion of these swimmers as they move through a microchannel, allowing options like oscillation, sticking to walls, or aligning with the centerline, which leads to different interactions with their surroundings.
Microswimmers need to maneuver independently in tight spaces such as microchannels within porous materials or blood vessels. These swimmers can come from biological sources, like algae or bacteria, or they might be specially designed structures intended for transporting chemicals and drugs. In these applications, controlling their swimming patterns relative to boundaries is crucial — for instance, they might need to exchange substances or information while avoiding unwanted attachment to surfaces.
Many microswimmers carry an electric charge, making it possible to use electric fields as a flexible method for navigating them through intricate environments. Researchers at MPI-DS investigated this concept in their experiments on self-propelling artificial microswimmers. Corinna Maass, the group’s leader at MPI-DS and an Associate Professor at the University of Twente, states, “We examined how a combination of electric fields and pressure-driven flow affects the motion of artificial microswimmers in a channel.” She adds that they identified specific motion modes and the system parameters that influence them. In earlier research, the team showed that their artificial swimmers tend to swim against the current while oscillating between the walls of the channel. With their latest findings, they’ve gained the ability to direct how the swimmers move by applying an electric field and flow in the channel.
As a result, the researchers created a wide variety of movement patterns: the swimmers can either stick to the channel walls or travel along the centerline, demonstrating oscillating or straight-line movement. They can even make U-turns if they head in the wrong direction. The team studied these different movement states using a broad hydrodynamic model that can be applied to any swimmer with an electrical charge. Ranabir Dey, an Assistant Professor at IIT Hyderabad, explains: “We demonstrate that the movement of charged swimmers can be more effectively controlled with external electric fields. Our model can aid in understanding and refining artificial microswimmers, offering inspiration for autonomous micro-robotics and other biotechnological innovations.”
