Dr. Alexander L. Yarin wants to make big changes in the world, and he’s researching nanotechnology to do it.
Yarin, a University of Illinois at Chicago distinguished professor, is the director of The Multiscale Mechanics and Nanotechnology Laboratory at the Department of Mechanical and Industrial Engineering. In the lab, he supervises approximately a dozen postdoctoral researchers and graduate students who are each concentrating on unique research focused on fundamental and practical aspects of fluid and solid mechanics, especially at length scales ranging from a few millimeters down to the nanometer level.
How small is a nanometer? “Nano” means one-billionth, therefore one nanometer is one-billionth of a meter. It’s quite difficult to visualize how small that is, so think about these examples. A human hair is approximately 80,000 to 100,000 nanometers wide, and a sheet of paper is about 100,000 nanometers thick.
“We are doing many things in the lab, but the central part is making nanofibers from polymer materials,” said Yarin as he walked across the 2,200 square-foot lab. “Now we aim at making self-healing nanofibers.”
For example, aircrafts have many components that are made mostly of composite materials. The aircrafts are subject to periodic load changes and can develop tiny fatigue cracks. There have been several incidents where tiny cracks — that were invisible — passed all the inspections. During the flights, the planes developed larger, visible cracks that forced emergency landings to avoid a catastrophe. In one case, the National Transportation Safety Board investigation confirmed that metal fatigue was the cause of the crack, and the damage was caused by pre-existing fatigue cracks.
“What you want to do is prevent such events,” said Yarin. “You want a material which operates like the human body, and repairs itself when it has some damage. We are working on self-healing materials.”
“The small nanofibers we create can be embedded in a tiny layer in the material and it acts like any blood vessels,” he said. “We put a monomer glue in the nanofiber, and when the nanofibers are cut by any tiny crack, the monomer is released and simultaneously a cure is released from a neighboring nanofiber. When the monomer and cure contact each other, they become solid and heal the damaged area.”
Yarin and his research team have several publications that prove the method works. Now, they are performing additional tests, like mechanical damage, corrosion, and fatigue tests with the material under permanent and periodic loads.
“A composite material with the self-healing nanofibers has a longer service life,” added Dr. Minwook Lee, who works in Yarin’s laboratory. “Without such self-healing nanofiber coatings, the metal corroded in a couple of days in an aggressive medium. With the self-healing fibers, it lasted more than 20 days.”
“We want it to last as long as possible,” said Yarin. “To prove the concept, we have to optimize the fiber structure and self-healing components used.”
Recycling to Reduce Pollution
In another section of the laboratory, Yarin’s team members are researching ways to recycle biowaste and keep it out of landfills.
Ethanol made from corn and biodiesel from soy create residual biowaste en masse. According to Yarin, biodiesel from soy uses only 20 percent of the soy mass. The rest is residual. It is not oil, but rather soy protein and it is considered a biowaste. However, the producers of biowaste are looking for something to do with it. Using the waste is an economical approach, because biodiesel is more expensive than regular diesel. By creating several accompanying products from soy protein, they will be sustainable and lower the cost of biodiesel.
“What we are doing here is developing new products from biowaste,” said Yarin. “We make nanofibers with these materials and they have many uses. Filtration is one of them.”
It goes without saying that water polluted with heavy metals pose a health risk. Unfortunately, there are places in the world where metals are present in the ground and people drink polluted water. To filtrate and purify water, people often use absorbents to remove heavy metals, but they can be expensive or ineffective. Recycling biowaste is one way Yarin is looking to make a difference.
“We are using nanofibers made from bioprotiens (biopolymers), because there is an abundant stock of biopolymers coming from agro-waste,” said Yarin. “We are using the biowaste to make nanofilters to either intercept very tiny nanoparticles from water or extract different heavy metals like lead from the polluted water.”
Apart from creating new products, Yarin views the repurposing of biowaste as an environmentally conscious decision. He notes that most of the material we have are man-made fibers derived from petroleum and its origin is probably overseas. But biowaste is coming from Iowa and Illinois and around the United States.
“Even a hotdog wrapper made from biopolymer will deteriorate very rapidly after being used — like the natural process,” he said. “The wrapper made from petroleum will not deteriorate in the ground for 100 years. Using local biowaste will reduce the amount of garbage piling up.”
Much like the materials that Professor Yarin is using, this is just a tiny example of the research that is underway in The Multiscale Mechanics and Nanotechnology Laboratory, which has the potential to profoundly change the world.
By David Staudacher