Latest news with #SushantaMitra
Gizmodo
3 days ago
- Science
- Gizmodo
Cool Physics Feat Makes a Sphere Roll Down a Vertical Wall
Scientists have discovered that under the right conditions, a gummy bear-like ball can roll down a vertical wall all by itself—upending a core assumption in physics. If you place a rigid sphere on a similarly rigid inclined surface, gravity will cause it to roll down said surface. But what happens if the surface, or plane, is completely vertical? Researchers had previously assumed that, without an initial push, the sphere would simply drop straight to the ground without rolling. New research, however, has just redefined this belief—as well as long-held assumptions in the field of physics. University of Waterloo researchers have revealed the exact scenario necessary to make a sphere roll down a vertical plane without physical intervention. While this niche observation might seem detached from everyday life, it could have useful applications for exploring hard-to-reach areas such as pipes, caves, and even space. 'When we first saw it happening, we were frankly in disbelief,' Sushanta Mitra, executive director of the Waterloo Institute for Nanotechnology, said in a university statement. The researchers describe their discovery as a challenge to 'our basic understanding of physics.' They 'double-checked everything because it seemed to defy common sense. There was excitement in the lab when we confirmed it wasn't a fluke and that this was real vertical rolling.' Mitra and his colleagues unexpectedly caught the vertical rolling with high-speed cameras, and explained their discovery in a study published in April in the journal Soft Matter. In their experiment, the vertical rolling depended on a precise balance of softness—scientifically defined as elasticity—between a small sphere and a vertical cellphone-sized surface. When the spheres were too solid, they simply fell directly to the ground. On the other hand, when they were too soft, they either slid down without rolling, or stuck to the plane. But a sphere about as soft as a gummy bear spontaneously rolled down a vertical surface equivalent to a spongy mouse pad at a speed of about 0.039 inches (one millimeter) every two seconds, as described in the statement. 'The key is that as it rolls, the sphere slightly changes shape at the contact point,' Mitra explained. 'The front edge acts as a closing zipper, while the back edge acts like opening it. This asymmetry creates just enough torque, or grip, to maintain rolling without either sticking or completely falling off.' The team's findings could have practical implications for the creation of soft robots that can scale vertical walls to explore or monitor inaccessible infrastructure and natural environments both on and off Earth. 'This opens up a whole new way of thinking about movement on vertical surfaces,' Mitra continued. 'Currently, robots and vehicles are limited to horizontal or slightly inclined surfaces. This discovery could change that.'
CTV News
7 days ago
- General
- CTV News
Researchers discover vertical ball drop at University of Waterloo
Surjyasish Mitra, Sushanta Mitra and A-Reum Kim, the team of researchers responsible for vertical ball drop discovery at the University of Waterloo. (Spencer Turcotte/CTV News) Balls usually roll horizontally but researchers at the University of Waterloo have done it on a vertical surface without applying any external force. 'Oh my God, this is not supposed to happen,' Surjyasish Mitra, a postdoctoral fellow involved in the research, told CTV News. He said his team was looking into something else and just happened to stumble upon it. Then it was balls to the wall to figure out what they were seeing. 'This marble will actually roll down, instead of just falling,' explained Sushanta Mitra, a UW mechanical and mechatronics engineering professor. 'It almost defies the laws of physics.' ball drop university of waterloo vertical surface The ball rolling under a microscope. (Source: University of Waterloo) The discovery hinged on finding the right balance of elasticity, or softness, between a pea-sized sphere and a vertical slide about the size of a cellphone screen. The ball was in their court to figure out how to bring their theory to life. The sponge-like material has the elasticity of a contact lens and the approximate consistency of a gummy bear. 'It is actually making some cracks. It is opening and closing the cracks almost like zippers. So, they are opening up, closing. By this virtue of opening and closing, it is able to propel this motion,' Sushanta Mitra said. Keeping their eye on the ball is a little tricky for researchers, even though it only rolls about one millimetre every two seconds. 'We repeated it multiple times to get the perfect video because it's under a microscope and the field of view is very limited,' said A-Reum Kim, a postdoctoral fellow. ball drop university of waterloo vertical surface Surjyasish Mitra, Sushanta Mitra and A-Reum Kim, the team of researchers responsible for vertical ball drop discovery at the University of Waterloo. (Spencer Turcotte/CTV News) The team is already figuring out how it can be put to good use. 'In some sort of human applications or robotic drug deliveries,' said Sushanta Mitra. 'Even for things like in Mars explorations, where you need these kinds of rolling motions without requiring any external agency.' Whatever it may be used for, they're having a ball thinking up endless possibilities for their discovery.
Scientific American
14-05-2025
- Science
- Scientific American
Wiggling Sperm Power a New Male Fertility Test
Sperm have to wiggle vigorously to reach an egg, and that motion is key to a clever new fertility test. The technique, tested with bull semen and detailed in Advanced Materials Interfaces, harnesses physics to make fertility testing easier and more cost-effective—and, if it works for human sperm, too, it might eventually help people tackle some conception issues from home. 'Fifty percent of families are facing a big challenge in terms of addressing fertility,' says Sushanta Mitra, a mechanical engineer at the University of Waterloo and co-author of the recent study. 'Our aim is to democratize that process.' Current laboratory tests for male fertility involve examining a semen sample under a microscope. Experts check the sperm cells' liveliness, which is considered a good proxy for fertility because the gametes need to quickly swim more than 1,000 times their body length to reach an egg. But these lab tests can be expensive and time-consuming. Meanwhile at-home tests tend to be less accurate because they often only detect the presence of certain proteins in sperm rather than assessing how the cells move. On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. The newly described method uses basic physics to measure sperm activity without costly equipment. The researchers placed droplets of bull semen at the end of a flexible plastic strip suspended next to a water-resistant surface. Next, they moved the surface toward the drop until it made contact and then moved it back to its original position. They measured how strongly each semen droplet stuck to the surface, via weak hydrogen bonds, as it was pulled away. If many highly active sperm were wiggling around inside the fluid, the hydrogen bonds broke more quickly, disrupting the drop's surface adhesion and making it break away earlier; the livelier the sperm, the less sticky the drop. 'It's exciting to be able to come up with a way to quantify sperm mobility at home,' says Stanford University urologist Tony Chen, who was not involved in the study. Mitra and his team hope to develop this technique into a cheaper, easier and more accurate home fertility test. 'There is a lot of stigma around male fertility,' Mitra says. Easier private testing could encourage people to evaluate semen quality more often, allowing them to check in while making lifestyle adjustments to perk up lethargic sperm, such as quitting smoking or reducing alcohol use. Such tests could also potentially be useful for breeding livestock. The researchers' next steps will be to standardize the tests and obtain benchmarks for different types of sperm, including human and bovine. Chen says clinical trials that evaluate droplets from many different patients will also be necessary to ensure the tests work with samples that have varying pH levels, white blood cell counts and fructose concentrations. 'There's more than just sperm in semen,' he says.
