Image of the force detector, a metal box with electrodes either end, a lens. Red and orange illustrate the movement of the atom when force is applied.

There’s only one atom at the heart of this force sensor. Image: CSIRO/Griffith University

What’s the faintest touch you can feel? A feather on the back of your hand, a whispered breath in your ear? Scientists from CSIRO and Griffith University just built a device that feels much lighter touches – in fact, it’s the most sensitive force detector on the planet!

To detect a tiny push, you need a tiny detector. The heart of this detector is a single atom, held in place with electricity. But it’s only held softly. When something pushes against the atom, it moves. To work out how hard the push is, scientists need to measure how far the atom travels.

Above the captive atom, there is a lens, almost like a tiny magnifying glass. This lens helps the team see how far the atom moves when touched. But there’s one problem. Looking down on the atom, it’s hard to tell how far up and down the atom moves. To solve this, the team deliberately unfocused the lens, making it blurry. They can tell how far up and down the atom moves based on whether it’s getting sharper or blurrier.

So how sensitive is it? Scientists usually measure force in newtons. A small feather weighing 0.03 grams pushes down on your hand with a force of about 0.3 millinewtons. This detector can measure forces of 100 zeptonewtons, about three million billion times weaker than the weight of that feather. Griffith University’s Dr Erik Streed says it best: “It’s about the same as the force of gravity between a person in Brisbane and a person in Canberra.”

Erik is planning to use the sensor to map out electrical forces surrounding interesting molecules. Other scientists are planning on integrating the tech into quantum computing experiments. There’s a lot of ways to use the world’s most sensitive force detector!

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