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Granular materials such as sand, sediment, grains and tiny particles may look simple, but when they begin to flow, they can display surprisingly complex behaviour. Add flowing water to the system, and things become even more interesting. In a new experimental study, Miles Morgan and his team investigated what happens when water is used to drive a dense bed of grains downward through a narrow vertical silo . They discovered several different flow patterns—including finger-like structures, porous flow and conventional silo flow—but one behaviour stood out: the sudden formation of straight, wormhole-like channels through the granular material. Once these channels appear, they can rapidly grow toward the outlet, creating a preferred pathway through which water and grains move while much of the surrounding material is bypassed. The discovery could help scientists better understand fluid-driven sediment transport and processes occurring in environments ranging from industrial systems to und...

Space exploration is entering a new era. Future astronauts are expected to spend months or even longer away from Earth as space agencies prepare for missions to the Moon and eventually Mars. But while rockets, habitats and life-support systems continue to improve, scientists are paying increasing attention to another challenge: what happens to the human skeleton during long periods in space? A new study published in Mayo Clinic Proceedings has found that astronauts who completed spaceflights lasting more than 90 days experienced higher rates of hip fractures than astronauts after shorter missions and people who had never traveled to space. The finding highlights an important concern for the future of human space exploration. Astronauts are generally selected for excellent physical health, but spending extended periods in microgravity can cause changes inside the body that may not be obvious when they return to Earth. Why Does Spaceflight Affect Bones? On Earth, our bones constantly r...

As humanity prepares for a new era of lunar exploration and future missions to Mars, scientists are studying a critical question: How will reduced gravity affect the human immune system? Astronauts will not experience Earth’s normal gravity on the Moon or Mars. The Moon has only about 16% of Earth’s gravity (0.16 g) , while Mars has about 38% (0.38 g) . Although these environments are not completely weightless, researchers are finding that even partial gravity can change how immune cells interact with blood vessels. A new study led by Yu Du and colleagues investigated how immune cells behave under lunar and Martian gravity. The researchers discovered changes in immune-cell movement, attachment to blood-vessel cells, adhesion molecules and the internal structure of endothelial cells—the cells that line our blood vessels. The findings suggest that partial gravity could influence the body’s ability to control inflammation and move immune cells through blood vessels. Why Immune Health Mat...

Asteroids may look like solid rocks from space, but many are actually loose collections of rocks, boulders and dust held together mainly by gravity and weak forces. These objects are known as rubble-pile asteroids , and understanding what lies inside them is crucial for explaining how they formed, changed over time and respond to forces such as rotation. Now, a study led by Yun Zhang and colleagues has used advanced computer simulations to investigate the hidden interior of Bennu , the 500-meter-wide asteroid explored in detail by NASA’s OSIRIS-REx mission. The results suggest that Bennu is much weaker internally than a solid rock, with a complex structure containing several stronger regions. The findings could also explain a major mystery: why Bennu does not have a moon, despite rotating fast enough for material to potentially escape its surface. Bennu Is Not a Solid Rock Scientists believe that many asteroids between roughly 200 meters and tens of kilometers across are rubble piles....

Imagine two small flying robots hovering almost directly above and below each other. Instead of keeping a safe distance, one robot carries a tool while the other reaches upward with a robotic arm, connects to that tool, and takes control of it—all while both machines remain in the air. This sounds extremely difficult because flying robots create powerful downward airflow called downwash . When multiple drones fly close together, this turbulent air can disturb their position and make precise movements much harder. Now, researchers led by Cao have developed a system called FlyingToolbox that demonstrates how flying robots can cooperate even under these challenging conditions. The system allows two aerial robots to operate in a vertical-stack formation and perform precise midair tool exchange with sub-centimetre-level accuracy . Why flying robots struggle when they get too close Multirotor drones, such as quadcopters, stay in the air by spinning their propellers and pushing air downward....

 What if a single sustainable material could be made rigid in one area, flexible in another and strong somewhere else—without joining different materials together? Researchers at the Institute for Bioengineering of Catalonia (IBEC) have developed a new approach that could make this possible. By adding tiny amounts of different metal ions to chitosan, the team found a way to locally control how stiff, strong and flexible the material becomes while keeping the same basic polymer. The research, published in the Journal of Materials Chemistry A , takes inspiration from one of nature’s most efficient designs: the insect exoskeleton. Learning from insect exoskeletons Modern products often depend on several different materials. A bottle may have a rigid body and a flexible cap or seal. Electronic devices can contain hard casings, soft protective layers and flexible components. Although combining materials can provide useful properties, it creates a major problem when the product reaches t...

Swimming through water requires considerable force, but a new experiment from MIT shows that even a single thin layer of living muscle cells can propel a tiny robot through water. Engineers have developed a paper-thin, muscle-powered swimming robot that uses genetically engineered cells and flashes of light to move, turn and navigate. The research, published September 28 in Advanced Functional Materials , introduces a new type of two-dimensional biohybrid robot —a machine that combines living biological tissue with engineered materials. Unlike conventional swimming robots that rely on motors, batteries and rigid mechanical parts, this tiny machine is powered by living skeletal muscle cells. A Robot Powered by Living Muscle At the heart of the new robot is a thin film of gel roughly the length and width of a stick of gum. The film acts as the robot's skeleton, while its two sides form flexible fins. Each fin is covered with a layer of living muscle cells that is thinner than a human...