Contact lenses have enabled people to see beyond the visible light range, picking up flickers of infrared light even in the dark – or with their eyes closed.

The lenses contain engineered nanoparticles that absorb and convert infrared radiation – specifically, a near-infrared wavelength range of 800 to 1600 nanometres – into blue, green and red light visible to the human eye. That is the same trick night-vision devices use to help people see in the dark, but the contact lenses weigh much less and require no additional power.

“The contact lenses would provide military personnel with discreet, hands-free night-vision capabilities that overcome the limitations of bulky night-vision [goggles or scopes],” says at Texas A&M University, who has done related research applying the same nanoparticles – sodium gadolinium fluoride, ytterbium and erbium – to eyeglass lenses.

The new wearables, developed by at the University of Science and Technology of China and his colleagues, don’t provide detailed night vision yet. That is because they can pick up only “high-intensity, narrowband LED” light sources, says Rentzepis, rather than lower levels of infrared light from ambient sources.

“It’s an audacious paper but, using just the contact lens, you wouldn’t be able to read a book in the infrared, or navigate down a dark road,” says at the University of Wisconsin-Madison, who was not involved in the research.

Instead, in tests on humans and mice, the contacts converted a normally invisible flash of infrared light into what Kats says should be a “big colourful blob of visible light”. Those blobs had uses, however. For example, Ma and his colleagues varied the frequency, number and colour of different light flashes to encode and transmit letters of the alphabet.

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This follows a previous study in which the researchers injected nanoparticles directly into the eyes of mice to provide infrared vision. The wearable contacts represent a “safer and more practical approach for human applications”, says Rentzepis. But they still come with potential health and safety risks, he notes, such as heat exposure from the light-conversion process and possible nanoparticle leakage into eye tissue.

A bottle can disinfect drinking water by channelling static electricity built up from just 10 minutes of walking – no limited supply of water purification tablets or external power sources required.

“Our water disinfection approach holds particular significance for populations in underdeveloped regions, isolated areas, disaster zones and conflict areas lacking adequate sanitation infrastructure,” says at Yonsei University in South Korea.

Kim and his colleagues took a reusable 500-millilitre water bottle and installed a polymer electrode inside that incorporates an array of nanorods made from the conducting polymer Polypyrrole. Those nanorods concentrate the electrostatic charges that accumulate on the human body during walking to create electric fields strong enough to kill or otherwise inactivate bacteria and viruses.

A small piece of aluminium foil attached to the outside of the bottle serves as a gripping point, while also collecting static electricity from the person’s hand, which then flows along a copper wire to reach the electrode inside the bottle.

Testing showed that this walking-powered method can completely disinfect river water containing both bacteria and viruses within 10 minutes – and sometimes faster if the person holding the bottle picks up the walking pace.

But the choice of footwear affects the amount of electrostatic charge harvested from the friction between the shoe materials and the ground. Shoes made from polycarbonate, rubber and polyvinyl chloride (PVC) enabled significantly higher electrical output than shoes made from leather, says at Renmin University of China, a coauthor on the study. And very humid conditions can also reduce the effectiveness of this method.

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Still, the self-sufficiency of this water disinfection method and the estimated cost of less than $2 per bottle could prove especially valuable in scenarios where people lack both clean water supplies and stable electricity.

The team is now focused on developing a more efficient manufacturing process for the nanorods. “We plan to develop commercially viable technology for affordable and sustainable portable containers for water purification,” says Huo.

Delivering medication to the lungs with inhalable nanoparticles may help treat chronic obstructive pulmonary disease (COPD). In mice with signs of the condition, the treatment improved lung function and reduced inflammation.

COPD causes the lungs’ airways to become progressively narrower and more rigid, obstructing airflow and preventing the clearance of mucus. As a result, mucus accumulates in the lungs, attracting bacterial pathogens that further exacerbate the disease.

This thick mucus layer also traps medications, making it challenging to treat infections. So, at Soochow University in China and his colleagues developed inhalable nanoparticles capable of penetrating mucus to deliver medicine deep within the lungs.

The researchers constructed the hollow nanoparticles from porous silica, which they filled with an antibiotic called ceftazidime. A shell of negatively charged compounds surrounding the nanoparticles blocked off pores, preventing antibiotic leakage. This negative charge also helps the nanoparticles penetrate mucus. Then, the slight acidity of the mucus transforms the shells’ charge from negative to positive, opening up pores and releasing the medication.

The researchers used an inhalable spray containing the nanoparticles to treat a bacterial lung infection in six mice with signs of COPD. An equal number of animals received only the antibiotic.

On average, mice treated with the nanoparticles had about 98 per cent less pathogenic bacteria inside their lungs than those given just the antibiotic. They also had fewer inflammatory molecules in their lungs and lower carbon dioxide in their blood, indicating better lung function.

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These findings suggest the nanoparticles could improve drug delivery in people with COPD or other lung conditions like cystic fibrosis where thick mucus makes it difficult to treat infections, says at the University of Massachusetts Amherst, who wasn’t involved in the study. However, it is unclear if these nanoparticles are cleared by lungs. “If you have a delivery system that builds up over time, that would be problematic,” he says.