Bacteria trapped — and terminated — by graphene filter

Airborne bacteria may see what looks like a comfy shag carpet on which to settle. But it’s a trapRice University scientists have transformed their laser-induced graphene (LIG) into self-sterilizing filters that grab pathogens out of the air and kill them with small pulses of electricity. The flexible filter developed by the Rice lab of chemist James Tour may be of special interest to hospitalsAccording to the Centers for Disease Control and Prevention, patients have a 1-in-31 chance of acquiring a potentially antibiotic-resistant infection during hospitalization. The device described in the American Chemical Society journal ACS Nano captures bacteria, fungi, fungi, prions, endotoxins and other biological contaminants carried by droplets, aerosols and particulate matter. The filter then prevents the microbes and other contaminants from proliferating by periodically heating up to 350 degrees Celsius (662 degrees Fahrenheit), enough to obliterate pathogens and their toxic byproducts. The filter requires little power, and heats and cools within seconds.

LIG is a conductive foam of pure, atomically thin carbon sheets synthesized through heating the surface of a common polyimide sheet with an industrial laser cutter. The process discovered by Tour’s lab in 2014 has led to a range of applications for electronics, triboelectric nanogenerators, composites, electrocatalysis and even art. Like all pure graphene, the foam conducts electricity. When electrified, Joule heating raises the filter’s temperature above 300 C, enough to not only kill trapped pathogens but also to decompose toxic byproducts that can feed new microorganisms and activate the human immune system. The researchers suggested a single, custom-fit LIG filter could be efficient enough to replace the two filter beds currently required by federal standards for hospital ventilation systems.

Seen in an electron microscope image, micron-scale sheets of graphene created at Rice University form a two-layer air filter that traps pathogens and then kills them with a modest burst of electricity

So many patients become infected by bacteria and their metabolic products, which for example can result in sepsis while in the hospital,” Tour said. “We need more methods to combat the airborne transfer of not just bacteria but also their downstream products, which can cause severe reactions among patients.

“Some of these products, like endotoxins, need to be exposed to temperatures of 300 degrees Celsius in order to deactivate them,” a purpose served by the LIG filter, he added. “This could significantly lessen the transfer of bacteria-generated molecules between patients, and thereby lower the ultimate costs of patient stays and lessen sickness and death from these pathogens.”

The lab tested LIG filters with a commercial vacuum filtration system, pulling air through at a rate of 10 liters per minute for 90 hours, and found that Joule heating successfully sanitized the filters of all pathogens and byproducts. Incubating used filters for an additional 130 hours revealed no subsequent bacterial growth on the heated units, unlike control LIG filters that had not been heated.

Bacteria culturing experiments performed on a membrane downstream from the LIG filter indicated that bacteria are unable to permeate the LIG filter,” said Rice sophomore John Li, co-lead author of the paper with postdoctoral researcher Michael Stanford. Stanford noted the sterilization feature “may reduce the frequency with which LIG filters would need to be replaced in comparison to traditional filters.” Tour suggested LIG air filters could also find their way into commercial aircraft.

Source: https://news.rice.edu/

Tool Speeds Up Manufacturing Of Powered Wearable

People could soon power items such as their mobile phones or personal health equipment by simply using their daily movements, thanks to a new research tool that could be used by manufacturers.

In a new paper published by Nano Energy, experts from the Advanced Technology Institute (ATI) at the University of Surrey (UK) detail a new  methodology that allows designers of smart-wearables to better understand and predict how their products would perform once manufactured and in use.

The technology is centred on materials that become electrically charged after they come into contact with each other, known as triboelectric materials – for example, a comb through hair can create an electrical charge. Triboelectric Nanogenerators (TENGs), use this static charge to harvest energy from movement through a process called electrostatic induction. Over the years, a variety of TENGs have been designed which can convert almost any type of movement into electricity. The University of Surrey’s tool gives manufacturers an accurate understanding of the output power their design would create once produced.

This follows the news earlier this year of the ATI announcing the creation of its £4million state-of-the-art Nano-Manufacturing Hub. The new facility will produce plastic nanoscale electronics for wearable sensors, electronic tags and other electronic devices.

Ishara Dharmasena, lead scientist on this project from the University of Surrey, said: “The future global energy mix will depend on renewable energy sources such as solar power, wind, motion, vibrations and tidal. TENGs are a leading technology to capture and convert motion energy into electricity, extremely useful in small scale energy harvesting applications. Our work will, for the first time, provide universal guidance to develop, compare and improve various TENG designs. We expect this technology in household and industrial electronic products, catering to a new generation of mobile and autonomous energy requirements.”

Source: https://www.surrey.ac.uk/