High-speed droplet production achieved in microfluidic devices

Japanese researchers have developed an efficient method to increase the speed of microdroplet generation for microfluidic devices, by incorporating so-called inverse colloidal crystal (ICC) structures into conventional microchannels. Their approach has been published in the journal Lab on a Chip.

Over the past two decades, microfluidic devices, which use technology to produce micrometre-sized droplets, have become crucial to applications including chemical reactions, biomolecular analysis, soft-matter chemistry and the production of fine materials. Furthermore, droplet microfluidics has enabled new applications that were not possible with traditional methods, by shaping the size of the particles and influencing their morphology and anisotropy.

Unfortunately, the conventional way of generating droplets in a single microchannel structure is often slow, limiting production. Researchers at Chiba University have now introduced a microfluidic system that utilises porous ICC structures to dramatically improve the efficiency of microdroplet generation.

“We considered that highly efficient droplet formation might be possible by using the numerous micropores formed on the surface of the ICC structure as droplet-forming nozzles,” said study leader Associate Professor Masumi Yamada.

“However, to the best of our knowledge, no study has been reported on the integration of inverse colloidal crystal structures into microfluidic channels and their application to highly efficient droplet formation. Therefore, we decided to develop a new microfabrication technique to integrate these structures into microfluidic channels to achieve efficient droplet formation.”

Spongy ICC structures were integrated with flat microchannels, which functioned like tiny nozzles to produce droplets around 1000 times faster than traditional microfluidic devices, at over 10,000 droplets per second. The size of the droplets could also be changed by adjusting the flow of liquids, their properties and the size of the tiny openings. Furthermore, single micrometre-sized particles made of natural biopolymers, like polysaccharides and proteins, were also produced using this method.

This new approach improves the existing concept of droplet microfluidics, not only by increasing the speed at which droplets are formed but also by making the process easier to create and operate. Due to the improved efficiency and control in the formation of droplets, it is expected to have a broad impact across different fields and product categories, including medicine, food, cosmetics, specialised inks and paints, sieving matrices for bioseparation and the creation of functional particles for displays and semiconductor applications.

“Microdroplets, biopolymer particles and vesicles fabricated from them as scaffolds are widely used for medical applications such as drug development and regenerative medicine,” Yamada said. “Additionally, this method is expected to be applied to the production of various substances, including carriers for the controlled delivery of drugs, scaffolds for cell culture, reagents for cell transformation, carriers of antigens in cellular immunotherapy and functional microparticles for diagnostics.”

Image caption: A schematic illustration depicting the generation of microdroplets through the integration of ICC structures into a microfluidic system. Image credit: Masumi Yamada, Chiba University.