From 325 metres away, your eyes can probably distinguish a person’s head from their body – and not much else. But a new laser-based device can create a three-dimensional model of their face.

at Heriot-Watt University in Scotland and his colleagues built a device that can create detailed three-dimensional images, including ridges and indentations as small as 1 millimetre, from hundreds of metres away. It uses an imaging technique called lidar, emitting pulses of laser light that collide with objects then reflect back into the device. Based on how long each pulse takes to return, lidar can determine an object’s shape.

To get to this level of detail, the team had to carefully calibrate and align many different components, says McCarthy, such as the tiny parts that direct the laser pulses inside of the device. To enable it to distinguish single particles of light, the researchers used a light-detecting sensor based on an incredibly thin piece of superconducting wire, a component that isn’t common in lidar. Filtering out sunlight that could enter the detector and degrade the image was another challenge.

The researchers tested their lidar system on a roof near their lab by taking detailed three-dimensional images of a team member’s head from 45 and 325 metres away. On a smaller scale, they captured Lego figurines from a distance of 32 metres.

In another test, they imaged a segment of a communication tower that was a kilometre away. “That was a very tough test – because of the bright background, and we had no control over what we could put in the scene [that we were imaging],” says McCarthy.

at the University of Science and Technology of China, whose team previously used lidar for imaging , says that McCarthy and his colleagues achieved “remarkable results” when it comes to the depth resolution of their device. “It is the best so far,” he says.

Lidar is only becoming more relevant for modern technology, says at Boston University in Massachusetts. He says that being able to create detailed three-dimensional maps of surroundings will be crucial for autonomous vehicles and even some robots – but the new device will have to be made smaller and more compact before it can be used for this purpose.

Small biofuel cells can harvest enough energy from the sweat on a person’s fingertips to power wearable medical sensors that track health and nutrition – and because our fingertips are one of the sweatiest parts of the body, the sensors could be powered all day.

at the University of California, San Diego, and his colleagues created a device that breaks down a dissolved compound in sweat called lactate. It comprises biofuel cells that fit into thin pads that are stuck to the fingertips. They soak up sweat into a thin layer of foam, where an enzyme oxidises lactate in the sweat to create an electrical charge.

Each finger pad can generate 20 to 40 microwatts of power and harvest 300 millijoules of energy per square centimetre during 10 hours of sleep. This isn’t enough to run power-hungry devices like smartwatches or mobile phones, but more than enough for lightweight sensors that detect a range of metrics such as heart rate, vitamin deficiencies and glucose levels.

Researchers have created devices that are powered by sweat before, but they needed large volumes of the liquid, such as when a subject was jogging. The fingertips have the highest concentration of sweat glands on the body and produce continuous charge even if the wearer isn’t exercising.

“Even with the minute amount of sweat compared to the sweat you got from a really intense workout, this power is still very sizeable,” says Yin. “No matter how clean your hand is, it’s very easy to leave your fingerprint everywhere. That’s basically the residue of your sweat, with a lot of metabolites. What we did is to take advantage of this.”

Currently, the enzyme that is key to the reaction begins to break down and become ineffective after two weeks. Yin says that further research is needed to create a stable enzyme that can be used in permanent sensors.

Pencil sketches on paper can be used as sensors that detect a variety of physiological signals, including heart rate, skin temperature and compounds in sweat.

Zheng Yan at the University of Missouri and his colleagues have developed electrodes made from pencil marks on paper that can pick up the body’s electrical signals when applied to the skin. The researchers believe it could be a cheaper alternative to other on-skin electrodes that cost more to produce and require materials such as copper or silicon.

The team created the electrodes by drawing mesh-like geometric sketches onto pieces of ordinary office copy paper. They then sprayed the paper with an adhesive to help it stick to human skin. They connected the pencil-and-paper electrodes to external data-recording hardware using a conductive cable.

The lines of graphite that a pencil makes on paper are conductive and can convey electrical signals that are present on the surface of human skin from underlying organs. An electrocardiogram (ECG), for example, records the heart’s electrical activity using electrodes fixed to the skin.

The researchers successfully used their electrodes to record ECG signals, heart rate and respiratory rate. They say the results were comparable in quality to conventional methods.

The devices could also detect skin temperature. “Electrical resistance reduces when the temperature of the pencil electrodes increases,” says Yan.

The electrodes were drawn with serpentine designs so that they would maintain their electrical properties even when stretched or bent, says Yan. “The electrical resistance in this case is determined by the length and cross-sectional area of these conductive traces,” he says.

When treated with certain chemicals, the electrodes can also be used to detect pH levels and compounds, such as uric acid and glucose, in sweat.

A different design was also able to harvest electrical energy from humidity in the air, sustaining a voltage of up to 480 millivolts for more than 2 hours.

Next, the team plans to develop pencil-and-paper-based electrodes with wireless capabilities, says Yan.

“The chips will be small and cheap enough to be built into clothing, allowing an AI to keep tabs on your BO”