ADVANCED MATERIALS & PROCESSES | JANUARY/FEBRUARY 2024 46 STRESS RELIEF DAILY GRIND SUPPORTS 3D PRINTING Researchers at the University of Colorado Boulder created a process for 3D printing a variety of objects using a paste made of old coffee grounds, water, cellulose gum, and xanthan gum. The team has already used the formula to print jewelry, plant pots, and espresso cups. Further, the technique is compatible with most consumer-grade 3D printers after a few modifications. The method is simple, according to assistant professor Michael Rivera. He and his colleagues mix dried coffee grounds with powdered cellulose gum and xanthan gum. Next, the researchers add water. “You’re pretty much shooting for the consistency of peanut butter,” says Rivera. However, the recipe cannot be loaded directly into a 3D printer. First, the researchers must modify a printer with plastic tubes and a syringe filled with coffee paste. The printed objects are surprisingly hardy: When dried, the coffee material is about as tough as unreinforced concrete. Rivera sees a lot of potential for turning coffee grounds into tangible objects such as small planters to grow seedlings for acid-loving plants like tomatoes. Once the plants are big enough, they can be placed into soil while still in their pots. The team can also add activated charcoal to the coffee grounds to make parts that conduct electricity, such as buttons for sustainable electronics. Rivera says that although printing with coffee grounds may not become a widespread practice, it could serve as another step toward 3D printing materials that could one day replace plastics. colorado.edu. A 3D printer uses old co ee grounds to make a flower planter. PRODUCE PROVIDES TEMPERATURE REGULATION Scientists at KTH Royal Institute of Technology in Stockholm developed a wood composite thermal battery made of coconuts, lemons, and modified wood. Researcher Peter Olsen says the material is capable of storing both heat and cold. If used in housing construction, his team says that 100 kilos of the material could save about 2.5 kWh per day in heating or cooling—assuming an ambient temperature of 24°C (75.2°F). In addition to sunlight, any heat source can charge the battery. The process involves removing lignin from wood, which creates open pores in the wood’s cell walls and removes color. The wood structure is then filled with a citrus-based molecule— limonene acrylate—and a coconut-based molecule. Limonene acrylate transforms into a bio-based polymer when heated, restoring the wood’s strength and allowing light to permeate. When this occurs, coconut molecules are trapped within the material, enabling the storage and release of energy. Coconut molecules can transition from solid to liquid to absorb energy, or from liquid to solid to release energy—similar to water freezing and melting. However, with the transparent wood the transition happens at a more comfortable temperature to allow heating or cooling of interior spaces. www.kth.se. Researchers are using coconuts, lemons, and modified wood for heating and cooling.
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