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Metal tubes that do not sink — Level A2 — Metallic arches rise from water against mountains.

Metal tubes that do not sinkCEFR A2

4 Feb 2026

Adapted from Luke Auburn-Rochester, Futurity CC BY 4.0

Photo by Logan Voss, Unsplash

Level A2 – High beginner / Elementary
2 min
120 words

Researchers at a university developed aluminum tubes that remain buoyant in water. They used an etching method to make tiny pits on the inside surface. These pits make the metal very water-repellent, called superhydrophobic (very water-repellent), so the surface stays dry.

When a treated tube enters water, it traps a stable air bubble inside. The trapped air keeps water out and the tube floats. The team added a divider in the middle so the air stays trapped even if the tube is pushed down. They tested tubes in rough water for weeks and found no loss of buoyancy. Many tubes can join into rafts for ships, buoys, or floating platforms and could harvest wave energy to make electricity.

Difficult words

  • superhydrophobica surface that strongly repels water
  • buoyantable to float on water or liquid
  • etchto make small marks or holes on metal
    etching
  • trapto hold something so it cannot escape
    traps, trapped
  • buoyancythe force that keeps things floating
  • harvestto collect energy or useful resources

Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.

Discussion questions

  • Would you like to use floating platforms made from these tubes? Why or why not?
  • How could floating tubes that collect wave energy help your community?
  • What problems might happen if many tubes float together in rough water?

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