A microfluidic nozzle system that fires a stream of tiny, but tough, carbon spheres could be used to produce carbon microbeads for applications ranging from pharmaceutical separation and purification to energy storage and drug delivery, its developers say1.
While there are plenty of ways to make carbon microstructures, few such materials could stand up to the high pressures that the microbeads can withstand, says Balaji Sitharaman, founder and director of materials manufacturing start-up Millennial Scientific, who led the work.
“While in academia, I worked on several strategies for assembling carbon materials,” says Sitharaman. “But they all resulted in brittle structures.”
They were thus unsuitable for applications requiring high mechanical strength, such as biomedical implants for supporting the healing of a broken bone. “The implant would crumble before it could help support bone growth to heal the break,” he says.
To create a tougher breed of carbon microbead, Sitharaman and his senior scientist, Michael Parente, turned to microfluidics. This technology allows liquids to be precisely manipulated at the microscale, potentially enabling the production of microbeads with physical properties tailored to specific purposes.
The team quickly discovered that off-the-shelf microfluidic setups were not up to the task. So they spent five years creating a custom-built microfluidic platform that was able to handle the high liquid viscosities and flow rates needed.
To demonstrate the potential of their new platform, the team targeted microbeads with high mechanical strength. They produced microbeads tailored to the demanding field of chemical chromatography—a technique used to separate mixtures of chemicals by forcing them through a tightly packed bed of microbeads under enormous pressure.
Sitharaman and his team generated microbeads of the necessary strength by formulating a viscous slurry of liquid carbon. They then injected this slurry through the nozzle of their microfluidic system into a fast-flowing stream of water. Like injecting oil into water, the two liquids did not mix, creating spherical carbon droplets in the water, which were solidified into microbeads by applying heat or ultraviolet light.
“Our microbeads could survive pressures of at least 9,000 pounds per square inch,” notes Parente.
The team’s next target is to demonstrate the adaptability of their microfluidics platform by making microbeads with different properties.
“Our goal is to manufacture designer microbeads by mixing and matching input materials and the processing parameters,” Sitharaman says. “By bringing in automation and machine learning, we can explore a large variety of parameters very quickly and identify structures with the optimal properties for a particular application.”
“A key benefit of our setup is its ability to scale up seamlessly.” he adds. “Our material synthesis platform allows production capacity from milligrams up to tens of kilograms per day.”
For drug-delivery applications, for example, the team is exploring polymeric microbeads as starting materials as they have already been approved by drug regulators for medical use. “We could fine tune the microbeads’ drug-release characteristics for each specific application,” Sitharaman says.
The team is also exploring using the platform to produce biocompatible inks for making 3D printed medical implants, which are tailored to support organ growth in a Petri dish and the healing of tissues ranging from skin to bone.
Reference:
1. Parente, M. J. & Sitharaman, B. Synthesis and characterization of carbon microbeads. ACS Omega 8, 34034–34043 (2023). https://doi.org/10.1021/acsomega.3c05042
A scientist–entrepreneur at Millennial Scientific, Dr. Balaji Sitharaman received his BSc from the Indian Institute of Technology at Kharagpur, MA, and his PhD from Rice University in Houston, Texas, where he also completed his postdoctoral research at the Richard E. Smalley Institute for Nanoscale Science and Technology. He was a tenured faculty member in the Department of Biomedical Engineering at the State University of New York at Stony Brook, USA. To date, he has published over 100 peer-reviewed scientific articles, which have received over 9,000 citations. In addition, he has received awards and funding for innovative basic and translational research from US federal agencies and private foundations, including the prestigious NIH Director’s New Innovator Award and the Wallace H. Coulter Translational Research Award. He is an inducted member of the National Academy of Inventors, USA.
