A collaboration between MIT, Boston University and German researchers has produced a new system that could soon be used to move tiny objects inside a microchip. The system is self-assembling, can be controlled via software and can transport particles up to 100 times the size of the beads carrying them. The objective is to give scientists new insights as to how cells and other objects are transported by tiny cilia throughout our bodies.

Throughout our bodies, tiny hair-like filaments known as cilia are used in organs such as the trachea and intestines to create currents that can effectively transport small particles where needed. The system devised by the team uses the same principle to move particles around a microchip.

Being able to effectively transport particles in microchips is a challenging task that could prove beneficial particularly to the biomedical field, where it could be used for anything from biomedical screening to pollution monitoring. Microfluidic devices have been advanced as a possible solution, but their design complexity — which requires precisely manufactured channels, valves and pumps — along with their relative lack of flexibility could be an obstacle to their widespread use.

This new system, however, offers improved control because the movement of the particles can controlled via software simply by adjusting a magnetic field in an approach that Alfredo Alexander-Katz, Professor of Materials Science and Engineering at MIT and part of the research team, refers to as "virtual microfluidics."

The system uses superparamagnetic beads, which are tiny polymer-based beads containing traces of magnetic material. When a rotating magnetic field is applied, the beads spontaneously form short chains which soon start spinning, creating currents that can effectively carry big particles along with them.

The magnetic field causes the chains to rotate and, even though they slip on the underlying surface, they slowly keep moving in the desired direction, and this imparts a directional flow to the surrounding fluid.

According to Prof. Alexander-Katz, applications to creating a new kind of microfluidics chips could be achieved within a year or so, because it would be simply a matter of scaling up from the simple systems that were tested in this study to more complex designs.

But the mechanism could also provide scientists with a way to simulate cilia in the laboratory and better understand how they work in living organisms by providing an easy way to test their theories. As for medical diagnostics, where it could allow controlled delivery of particles inside the body to specifically targeted locations, a system may take several years to develop because of the stringent requirements for safety testing.