Researchers at Tel Aviv University have developed a micro-robotic navigation approach that allows microscopic devices to move across multiple surfaces in three-dimensional space, overcoming a longstanding constraint that has typically restricted such machines to a single continuous plane, according to a study published in the journal Nature Communications. Led by doctoral student Ido Rachbuch, researcher Dr. Sinwook Park, and Prof. Gilad Yossifon of the institution’s School of Mechanical Engineering and School of Biomedical Engineering, the work introduces a hybrid propulsion system using magnetic and electric fields to control microscopic Janus particles.
How Magnetic and Electric Fields Power 2.5-Dimensional Navigation
Measuring between 10 and 30 microns—roughly the size of a biological cell—these micro-robots cannot carry onboard motors, batteries, or control systems, necessitating off-board control via external forces, according to the study. To achieve mobility beyond a flat surface, the Tel Aviv University team utilized Janus particles, which are tiny spherical objects with halves of differing properties. One hemisphere features an electrically conductive material, while the other contains a magnetic layer.
The two external fields perform distinct, complementary functions. The magnetic field governs orientation, rolling motion, and lifting, while the electric field supplies propulsion, drives surface adhesion, and manages the reversible capture and release of microscopic cargo. This combined system enables the devices to transition from the floor to the ceiling of a microfluidic chamber, as well as intermediate surfaces, creating what the researchers describe as “2.5-dimensional navigation.” Rather than hovering freely like miniature drones, the micro-robots travel horizontally and vertically while maintaining controlled contact with different planes.
Laboratory Demonstrations with Live E. Coli Bacteria
During laboratory testing, the research team used real-time closed-loop control to guide the robots over microscopic walls and obstacles, across elevated surfaces, and back down to the ground along predetermined paths. Beyond basic locomotion, the experiments demonstrated cargo transport capabilities. According to the findings, the micro-robots collected plastic particles and live Escherichia coli (E. coli) bacteria, carried them over physical barriers, and released them at targeted locations.
Viability tests confirmed that the transported bacteria remained alive after the journey, indicating compatibility with delicate biological environments. Accompanying video documentation released by Tel Aviv University highlights three specific demonstrations: a micro-robot rolling magnetically along a chamber ceiling before descending when the electric field is deactivated; a device climbing and traversing an obstacle; and a micro-robot capturing, transporting, and releasing live E. coli bacteria on the opposite side of a barrier.
Potential Applications in Lab-on-a-Chip Systems
The technology offers a new platform for precision tasks in microscopic environments, according to the research team. Potential applications include transporting cells and biological materials within lab-on-a-chip systems, sensing and stimulating individual cells, and automatically assembling microscopic structures.
“The challenge in micro-robotics is not only moving tiny robots but navigating them in a controlled way and giving them freedom to operate in complex environments,” Prof. Gilad Yossifon stated, according to the study. “In this study, we showed how a synergistic combination of magnetic and electric fields allows even basic micro-robots to perform navigation and tasks that previously required more complex systems. The ability to move through multilayer environments opens new possibilities for lab-on-a-chip applications, biomedical engineering and a new generation of micro-robotic systems.”
Did You Know?
In materials science, the term refers to particles whose surfaces possess two distinct physical or chemical properties.
Frequently Asked Questions
What are Janus particles?
Janus particles are tiny spherical particles whose two halves possess different properties. In this study, one hemisphere is electrically conductive while the other contains a magnetic layer.
How do these micro-robots move without batteries?
Because they measure only 10 to 30 microns in size, they cannot carry onboard power sources. Instead, they rely on external magnetic and electric fields for propulsion, orientation, and control.
Can these micro-robots handle biological materials?
Yes. Laboratory experiments demonstrated that the devices can capture, transport over physical barriers, and release live E. coli bacteria without compromising their viability.
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