Scientists create tattoos you can switch on and off with light
A University of Colorado Boulder team has made photochromic inks that appear under UV light and fade again in bright light, with colours still switchable after two years in skin.
Science
Can a woolly bear caterpillar really predict the winter? Here is what scientists say
Folklore says the caterpillar's black and brown bands forecast how harsh winter will be. Entomologists are not convinced.
Hidden until needed: how switchable tattoo ink could help cancer patients
Radiotherapy patients often carry permanent alignment tattoos. A new light-activated ink could keep those marks invisible except in the clinic.
How woolly bear caterpillars survive being frozen all winter
The fuzzy caterpillar famous for "predicting" winter has a real superpower: it lets its body freeze, then thaws out in spring.
Why are more roofs not made of solar tiles? The trade-offs explained
Solar tiles look like an ordinary roof and suit conservation areas, but they cost more, produce less and need a full re-roof. Here is who they make sense for.
The forgotten experiment that paved American streets with crushed glass
Since the early 1970s, engineers have tested "glasphalt", asphalt made partly from waste glass. It works, within limits, and here is why it never became the norm.