Water shortage is one of the world’s biggest challenges. The World Health Organization (WHO) thinks one in three people globally do not have easy access to clean water. Desalinating (给……脱盐) ocean water could help. But currently-available desalination units typically require high-pressure pumps (泵) to push water through filters (过滤器), which makes it difficult to reduce their size without influencing the energy-efficiency of the device. Meanwhile, they are too expensive to set up widely.

Now, Massachusetts Institute of Technology (MIT) researchers have developed a convenient desalination machine. Unlike traditional desalination units that need replaceable filters, the MIT machine uses electricity to remove the salt and other small things from the ocean water. More importantly, the suitcase-sized device needs less power to run than a cell phone charger. It can also be powered by a small solar panel that costs less than $50. The lack of filters and the low electricity requirements make the machine extremely cheap to set up. “Even a kindergarten student can carry and use the desalination unit,” said one researcher. “Ease of use was one of the main motivations for creating the device.”

After running lab experiments using water with different salinity and turbidity (cloudiness) levels, they field-tested the device at Boston’s Carson Beach. The researchers set the box near the shore and put the feed tube into the water. In about half an hour, the device had filled a plastic drinking cup with clear, drinkable water.

The researchers believe their invention can deliver drinking water meeting WHO quality standards with a push of a button. Meanwhile, a smartphone app allows the user to control the unit wirelessly and receive real-time data on power consumption and water salinity. It also sends out information when the water is drinkable.

The MIT team is now exploring ways to bring their portable machine to market. They believe it will benefit residents of small islands or those running away from natural disasters. It could also be very useful for sailors on cargo ships and small groups of soldiers on long-term military missions.

Implanted (植入的) devices, such as heart pacemakers, are a valuable part of modern medicine. Their use, however, is limited by the need to renew their batteries and this is a particular problem for those inside the wearer’s head. Therefore, a way to power such implants without replacing their batteries at all would thus be welcome. And Dr Hyuck Choo and his colleagues think they have one. They plan to collect the necessary energy from the vibrations(震动) that occur when someone is talking.

DrChoo’s power plants are small sheets of lead zirconate titanate, a material that produces electricity when it vibrates. He knew that sheets of the size he chose have a resonance (共振) at around 690Hz. This is well above the normal range of the human voice. Using larger sheets would lower the resonance frequency. So he sought to lower a sheet's resonance frequency without increasing its area by caring a special shape out of it. And it worked!

When Dr Choo and his colleagues tested the carved sheets by exposing them to a range of frequencies and monitoring the amount of electricity generated, they found that the voltage was between 100Hz and 120Hz (approximately the common frequencies of adult male vices), and also between 200Hz and 250Hz (the female voice s common frequencies). And, although the amount of power produced is not huge, it seems adequate for the task.

As Dr Choo reported at a conference on January 26, he and his team were able to harvest a tenth of a mill watt per square centimetre of lead zirconate titanate from the voice of a man talking at 70 decibels (分贝), which is normal speaking volume, and tents from someone shouting at 100 decibels Implants usually require a tenth of a mill watt or less to function so this suggests a practical device might be within reach-especially as the vibrations produced by the voice travel efficiently up through the skull, meaning the generator could be put into an implant.

Phone batteries rarely last a full day anymore, so carrying compact chargers(小巧的充电器) is becoming normal. But many of these so-called portable devices are heavy, thick and inconvenient—until Solar Paper is developed.

Chicago engineers have designed a super-thin, lightweight panel (面板) called Solar Paper capable of charging an iPhone in two hours and many panels can be combined to boost its power. It was created by Chicago-based Yolk. After raising more than $1 million online for the production, it is now available to purchase throughout the country. It comes in four versions －2.5W, 5W, 7.5W and 10W－depending on the output needed for various devices. And these different models are created by combining individual 2. 5W panels together.

A 2.5W panel will charge an iPhone 6 or Galaxy S3 in five hours. The 5W version charges the same devices but cuts charging time to two hours or three hours if it’s cloudy. The 7.5W model Solar Paper charges the devices in the same time as the 5W version but produces more energy when it is cloudy. The 10W version is ideal(理想的) for the iPad Air 2, and will charge a device in 2.5 hours. Each individual panel measures 3.5 inches×6-7 inches×0.6inches, weighs 60g and is 1.5mm thick.

Other features include a unique automatic reset(重置) function which stops and starts the Paper charging when cast with a shadow or placed in sunlight. Other solar chargers require you to re-plug the wire at these conditions. It also has a low-energy LCD screen that displays the amount of power the Solar Paper produces in real time.