Microfluidic Self-Assembly

Technology Review

TECHNOLOGY REVIEW: When it comes to building microscopic devices, one of the most promising ideas is to exploit the process of self-assembly. In this way, complex structures can be created by combining building blocks under natural circumstances.

This kind of self-assembly mechanism dominates at the molecular scale, where it is responsible for the construction of most biomolecules. At the heart of this mechanism is Brownian motion which effectively mixes and jiggles molecules so that they rapidly find their place in incipient structures. This is a powerful process that can form hugely complex machines such as the ribosome, a molecular device for synthesizing proteins.

One recent idea is to use colloids rather than molecules as the building blocks for even more advanced structures. Colloids are insoluble, nanometre-scale particles mixed in water. These particles can be chemically engineered to bind together to form specific structures.

But as the building blocks become bigger, it takes longer for Brownian motion to jiggle the blocks into the appropriate locations. So self-assembly take significantly longer. In fact, it can take thousands of seconds to synthesise a single colloidal molecule. At that rate, a millimetre cube containing 1 billion colloidal molecules would take 30 years to form.

Clearly, that is far too slow for any kind of industrial process, so chemists have been looking for ways to speed up colloidal self-assembly. Today, Bingqing Shen at ESPCI (the Paris Institute of Technology) in France and a few buddies say they’ve found an entirely new way to assemble structures on this scale that should reduce manufacturing time by orders of magnitude.

Physics arXiv:
Self-Assembly Driven By Hydrodynamic Interactions In Microfluidic Devices
Bingqing Shen, Joshua Ricouvier, Mathilde Reyssat, Florent Malloggi, Patrick Tabeling