ADVANCED MATERIALS & PROCESSES | OCTOBER 2023 56 3D PRINTSHOP ‘LIVING MATERIAL’ MAY CLEAN POLLUTED WATER A seaweed-based polymer combined with genetically engineered bacteria could offer a sustainable way to clean pollutants from water. The researchers from the University of California San Diego fed the “living material” into a 3D printer and found that a grid-like structure was optimal for keeping the bacteria alive. The bacteria were also engineered to self- destruct in the presence of a molecule called theophylline, which is often found in tea and chocolate. This offers a way to eliminate them after they have done their job. The chosen shape has a high surface area to volume ratio, which places most of the cyanobacteria near the material’s surface to access nutrients, gases, and light. The increased surface area also makes the material more effective at decontamination. The researchers also developed a way to eliminate the cyanobacteria after the pollutants have been cleared. They genetically engineered the bacteria to respond to a molecule called theophylline. The molecule triggers the bacteria to produce a protein that destroys their cells. “This way, we can alleviate any concerns about having genetically modified bacteria lingering in the environment,” says Jon Pokorski, a professor of nanoengineering at UC San Diego who co-led the research. A preferable solution, the researchers note, is to have the bacteria destroy themselves without the addition of chemicals. This will be one of the future directions of this research. “Our goal is to make materials that respond to stimuli that are already present in the environment,” adds Pokorski. ucsd.edu. MOLECULE HELPS POLYMERS WITHSTAND TEMP FLUCTUATIONS Researchers at Sandia National Laboratories have developed a molecule that can easily be incorporated into a polymer to change its properties. The molecule helps change the way some materials react to temperature fluctuations, making them more durable. “This really is a unique molecule that when you heat it up, instead of it expanding, it actually contracts by undergoing a change in its shape,” says Erica Redline, a materials scientist who leads the team. “When it’s added to a polymer, it causes that polymer to contract less, hitting expansion and contraction values similar to metals.” Another key to this invention is that it can be incorporated into different parts of a polymer at different percentages through 3D printing. “You could print a structure with certain thermal behaviors in one area, and other thermal behaviors in another to match the materials in different parts of the item,” adds Sandia chemical engineer Jason Dugger. Another benefit is helping reduce the weight of materials by eliminating heavy fillers. The team is working to scale up production and reduce the number of steps required to build the molecule. They have been approached by an epoxy formulator who believes this molecule could be incorporated into adhesives. sandia.gov. Sandia National Laboratories chemist Chad Staiger uses a separatory funnel to remove byproduct from the synthesis of a molecule. Courtesy of Craig Fritz/Sandia National Laboratories. The living material is 3D-printed as a grid-like structure. Courtesy of UC San Diego.
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