Science & Technology, Singapore (Commonwealth Union) – Two groundbreaking studies have revealed the potential of aerogels to provide cooling for buildings as well as guarding from electromagnetic waves emitted by electronic devices. Aerogels, known for their highly porous nature and low density, have been traditionally used for thermal insulation in the aerospace industry. However, researchers from the National University of Singapore (NUS) have discovered new applications for these versatile materials.
In one study, the researchers, led by Associate Professor Duong Hai-Minh, developed aerogels for radiative cooling and electromagnetic wave (EMW) absorption. The team created thin-film aerogels from plastic waste, which can function as thermal insulators and radiative coolers when applied to surfaces like building roofs. This innovative solution offers energy-free thermal management and can significantly reduce internal temperatures.
In another study, the researchers devised a scalable method to produce aerogels that absorb EMWs in the X-band, used in weather monitoring and air traffic control. These lightweight, durable aerogels protect against electromagnetic pollution, shielding both humans and sensitive equipment in our increasingly digital world. Both studies highlight the immense potential of aerogels in various applications, from building and construction to environmental remediation, drug delivery, and textiles. The NUS research team’s findings have been published in the journals Solar Energy and Carbon, paving the way for further exploration and development of these remarkable materials.
The NUS team’s innovative research expands upon their previous achievements in creating aerogels from various waste materials, including plastics, paper, and agricultural by-products like pineapple leaves. Researchers of the study pointed out that these aerogels offer a passive cooling solution, unlike traditional energy-intensive air conditioners that consume around 20% of electricity in buildings globally. By harnessing the power of radiative cooling, these aerogels can dissipate heat into space without taking up energy, providing a sustainable and efficient alternative for cooling systems.
“This process involves using specially engineered aerogels to emit infrared radiation through the atmospheric ‘sky window’, effectively cooling surface temperatures below ambient levels,” Associate Professor Duong explained. “We are excited to be able to upcycle fibres from disposable polyethylene terephthalate (PET) bottles for the new aerogels designed for this purpose, to help address the global plastic waste crisis.”
The team previously utilized PET fibres in creating aerogels, but their new technique is considerably more energy-efficient, using 97% less energy and cutting production time by 96%. In tests conducted in Singapore’s warm climate, in partnership with Dr Jaesuk Hwang from the Centre for Quantum Technologies at NUS, a 0.5-centimeter layer of the material generated a 2-degree Celsius cooling effect. This was achieved by emitting infrared heat into the surroundings and demonstrating excellent heat insulation, thereby putting a stop to heat absorption from the surrounding atmosphere.
“These aerogels could reduce energy consumption in both residential and commercial buildings, especially in tropical climates where cooling is now a necessity,” said Associate Professor Duong.
Future studies will concentrate on tailoring these aerogels for various climate conditions and broadening their uses beyond building insulation. This will include applications in industrial processes where efficient thermal management of liquid circulation pipes is vital.
The researchers stated that electronic devices currently emit EMWs that can interfere with nearby equipment and pose health risks, such as DNA damage and cancer. Therefore, it is essential to develop materials that can effectively absorb EMWs, shielding both humans and infrastructure from these negative effects. Potential applications consist of enhancing the privacy and security of buildings, as well as safeguarding sensitive medical equipment.
To meet this demand, Associate Professor Duong’s team has created a scalable and environmentally friendly method to produce innovative aerogels that have the ability to absorb EMWs. The process involves combining three primary components – carbon nanotubes, polyvinyl alcohol, and carboxymethyl cellulose – where the freeze-drying process is then carried out. The aerogel, approximately 3 millimeters thick or the width of 40 strands of human hair, showed an exceptional performance by absorbing 99.99 percent of EMW energy. Throughout the entire X-band (8.2-12.4 GHz) of the electromagnetic spectrum, primarily used for radar systems, weather monitoring, and air traffic control, the aerogel consistently displayed its ability to absorb 90% of EMW energy.
“In addition to offering a wide absorption bandwidth of 1.2–2.2 GHz in the X-band, our aerogel is also about 10 times lighter than existing composites used for EMW absorption,” said Associate Professor Duong. “Unlike other composites, our aerogel requires no mixing with heavy polymer fillers before use.”
