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Driscoll Research Discovers New Way to Trap Microparticles

March 16, 2023

Text taken from Northwestern Now Article- Click here to read the full article

When physicists steered a tiny microparticle toward a cylindrical obstacle, they expected one of two outcomes to occur. The particle would either collide into the obstacle or sail around it. The particle, however, did neither.

The researcher team — led by Northwestern Physics and Astronomy's own Michelle Driscoll and École Polytechnique in France — was surprised and puzzled to watch the particle curve around the obstacle and then stick to its backside. The obstacle, it seemed, had the particle effectively trapped. 

After a series of simulations and experiments, the researchers unraveled the physics at play behind this strange phenomenon. Three factors caused the unexpected trapping behavior: electrostatics, hydrodynamics and erratic random movement of the surrounding molecules. The size of the obstacle also determined how long the particle remained trapped before escaping. 

The new insights could be leveraged to advance microfluidic applications and drug delivery systems — both of which rely on microparticles to navigate complex, structured landscapes.

The study was published in the journal Science Advances on March 8.

“I didn’t expect to see trapping in this system at all,” said Michelle Driscoll, who co-led the study. “But trapping adds a lot of utility to the system because now we have a way to gather up particles. Tasks like trapping, mixing and sorting are very difficult to do at such small scales. You can’t just scale down standard processes for mixing and sorting because a different kind of physics kicks in at this size limit. So, it’s important to have different ways to manipulate particles.”