Researchers have developed and demonstrated an efficient and scalable technology that allows them to fabricate soft polymer materials into dozens of different structures, or “shapes,” from ribbons and nanosheets to rods and branched molecules. This technology allows users to precisely tune the morphology of materials on the micro and nanoscale.
“This advance is important because the technology can be used with a variety of polymers and biopolymers. Because the morphology of these polymer micro- and nanostructures is critical for their applications, it allows us to obtain new polymer functionalities by simply controlling the structure rather than the polymer chemistry,” he says. says Orlin Filev, corresponding author of the paper and S. Frank and Doris Culberson Distinguished Professor of Chemical and Biological Molecular Engineering at North Carolina State University. “For example, nanosheets could be used to design better batteries, while dendritic colloids—branched networks of polymer fibers with an exceptionally high surface area—could be used in environmental remediation technologies or the creation of new, lightweight materials.”
Basically, all the different shapes are produced using a well-known process called polymer deposition. In this process, a polymer is dissolved in a solvent, which results in a polymer solution. This polymer solution is then introduced into another liquid, which causes the polymer to come back together as a soft material.
What’s new here is that the researchers figured out how to precisely control the structure of the resulting soft polymer by manipulating three sets of parameters during the manufacturing process.
The first set of parameters is the shear rate, which indicates how quickly the fluids stir when the two fluids are mixed together. The second set of parameters is the polymer concentration in the polymer solution. The last set of parameters is the composition of the solvent in which the polymer was initially dissolved, as well as the composition of the liquid to which the polymer solution was added.
“We identified critical parameters that influence the final shape of the polymeric materials, which in turn gives us great control and versatility,” says Rachel Pang, first author of the paper and a recent Ph.D. Graduated from North Carolina State. “Because we now understand the role of each of these factors and how they all affect each other, we can iteratively reset the morphology of polymeric particles.”
“Although we’ve shown how to produce dozens of different shapes, we’re still in the early stages of exploring all of the potential outcomes and applications,” says Filev.
Researchers have already demonstrated that dendritic colloids can be used to make membranes for the growth of living cells, or to create hydrophobic or hydrophilic coatings. The researchers also worked with collaborators to demonstrate that the nanosheets have potential as more efficient separators in lithium-ion batteries.
“This technology can also be used with a variety of natural biopolymers, such as plant proteins, and can be used to support a variety of applications, such as the development of plant-based meat analogues, which require precise control over the shapes of protein molecules at multiple length scales,” adds the co-author. Professor Semyon Stoyanov of the Singapore Institute of Technology and Wageningen University in the Netherlands. “In addition, because our technology is based on mixing liquids using conventional mixers, it can be easily scaled up for practical manufacturing.”
“We are currently working with food science researchers to determine how protein microdomains can be used to control the texture of certain food products,” says Filev. “We are also working with collaborators to explore how our technology can be used to produce biopolymer-based materials for use in biodegradable soft electronics.
“We are open to working with additional collaborators to explore the potential applications of polymers and biopolymers in all of these forms.”
NC State has issued or pending patents regarding shear fabrication of microrods, nanofibers, and colloidal capillaries and their application in electrochemical energy sources.
This work was accomplished with support from the National Science Foundation’s Nanofabrication Program, under grant CMMI-1825476. The work has received additional support from NSF under grants EFMA-2029327 and CMMI-2134664.
