You may have had a children's toy that had a wheel with a coiled string or rubber band coming out from each side. You would pull on the strings and the wheel would spin .. it's a non-linear oscillator. Every time you pull the strings you're putting energy into uncoiling and into spinning the wheel. (this problem is often given in Physics mechanics courses). There are some loses, but they can be efficient.
Someone connected the toy with the need for an inexpensive centrifuge that doesn't use electricity for the developing world. People have tried salad spinners, but they're way too slow - about 6oo rpm. This one hit 125,000 rpm with 60,000g s at the spinning wheel. Just the ticket for separating blood components. Couple this with a smartphone microscope and you can do serious good work.
Nature has posted the paper outside their paywall. It has a bit of undergrad level physics... but go in even if that's not interesting... there are some great videos at the end of the paper.
Hand-powered ultralow-cost paper centrifuge
M. Saad Bhamla, Brandon Benson, Chew Chai, Georgios Katsikis, Aanchal Johri & Manu Prakash
Abstract In a global-health context, commercial centrifuges are expensive, bulky and electricity-powered, and thus constitute a critical bottleneck in the development of decentralized, battery-free point-of-care diagnostic devices. Here, we report an ultralow-cost (20 cents), lightweight (2 g), human-powered paper centrifuge (which we name ‘paperfuge’) designed on the basis of a theoretical model inspired by the fundamental mechanics of an ancient whirligig (or buzzer toy; 3,300 BC). The paperfuge achieves speeds of 125,000 r.p.m. (and equivalent centrifugal forces of 30,000 g), with theoretical limits predicting 1,000,000 r.p.m. We demonstrate that the paperfuge can separate pure plasma from whole blood in less than 1.5 min, and isolate malaria parasites in 15 min. We also show that paperfuge-like centrifugal microfluidic devices can be made of polydimethylsiloxane, plastic and 3D-printed polymeric materials. Ultracheap, power-free centrifuges should open up opportunities for point-of-care diagnostics in resource-poor settings and for applications in science education and field ecology.
A centrifuge is the workhorse of any medical diagnostics facility. From the extraction of plasma from whole blood (for performing immunoassays or determining the haematocrit value), to analysing the concentration of pathogens and parasites in biological fluids, such as blood, urine and stool (for microscopy), centrifugation is the first key-step for most diagnostic assays 1 . In modern diagnostics, separation of unwanted cellular debris is especially critical for the accuracy and reliability of molecular diagnostics tools and lateral-flow-based rapid diagnostic tests 2 that are designed for detecting low levels of infection in diseases such as malaria, human immunodeficiency virus and tuberculosis 3,4,5 . Currently, centrifugation is typically inaccessible under field conditions, because conventional machines are bulky, expensive and electricity-powered 4 . The need for electricity-free centrifugal bio-separation solutions has prompted researchers to use egg-beaters and salad-spinners as proposed devices 6,7 . However, these suffer from bulky designs and extremely low rotational speeds (maximum 1,200 r.p.m.; 300 g), leading to impractical centrifugation times for a simple task of blood plasma separation (>10 min). Thus, a low-cost, portable, human-powered centrifuge that achieves high speeds is an essential, yet unmet need, especially for diagnostics in resource-limited environments 8,9,10 .
We describe the design and implementation of an ultralow-cost (<20 cents, Supplementary Table 5), lightweight (2 g), field-portable centrifuge, henceforth referred to as a ‘paperfuge’ and inspired by historic whirligig (or buzzer) toys (Fig. 1a). We demonstrate that the paperfuge achieves speeds of 125,000 r.p.m. (30,000 g) using only human power. Using a combination of modelling and experimental validation, we uncover the detailed mechanics of the paperfuge and leverage this understanding to construct centrifuges from different materials (in particular, paper and plastic). We demonstrate applications including plasma separation, quantitative buffy coat analysis (QBC) and integrated centrifugal microfluidic devices for point-of-care (POC) diagnostic testing.
Forests are potent carbon sinks, but also the oceans' seagrasses can store enormous amounts of carbon. A little bay in Denmark stores a record amount of carbon. Here is the secret.
Seagrass plays a bigger role in the Earth's carbon cycle than most of us think. The underwater meadows of seagrass are capable of storing large amounts of carbon - a talent that draws attention in a time, where decision makers and scientists are searching for ways to bring down the release of CO2 to the atmosphere.
In the past year the climate in the Arctic has at times bordered on the absurd. Temperatures were 30 to 50 degrees Fahrenheit above average in some places during the recent Christmas week. Through November the area of ice-covered ocean in the region reached a record low in seven of 11 months—an unprecedented stretch. More important, perhaps, the difference between Arctic temperatures and those across the midlatitudes of North America, Europe and Asia during 2016 was the smallest ever seen.
That narrowing gap is important to note because it seems to be driving extreme weather in the midlatitudes, from heat waves and droughts to heavy snowfalls. Why is the Arctic so crazy lately, and how strong is the connection to bad weather to its south, where so many people live? Scientific American asked Jennifer Francis, who is a research professor at the Institute of Marine and Coastal Sciences at Rutgers University and has investigated Arctic climate change and its links to weather worldwide since 1994.
Behold the hyolith — a bizarre Cambrian-period creature that dwelt on the ocean floor alongside other armored invertebrates like trilobites more than 500 million years ago. Its body was encased in a pair of shells that resembled an ice cream cone with a lid like a trap door. Two tusklike spines protruded from the soft tissue near the hinge, and on top of its mouth was a row of fluttering tentacles.
Since its discovery in the 19th century, the hyolith has puzzled paleontologists. Some thought it was a mollusk, like a snail or clam. Others said it belonged to its own group of animals.
Joseph Moysiuk, an undergraduate student at the University of Toronto, thinks he has solved the mystery.