Doctors know that we need smarter medicines to target the bad guys only. One hope is that tiny robots on the scale of a billionth of a metre can come to the rescue, delivering drugs directly to rogue cancer cells. To make these nanorobots, researchers in Europe are turning to the basic building blocks of life – DNA. Today robots come in all shapes and sizes. One of the strongest industrial robots can lift cars weighing over two tons.

Since research in synthetic biology began nearly two decades ago, the field has expanded beyond its original mandate of using engineering principles to study and manipulate cells. Today, scientists are building biological computers and DNA-based robots that can carry out logical operations and complete tasks. These miniscule machines look nothing like laptops or Roombas. Yet, algorithms still guide the robots through tasks, and the biological computers funnel inputs through logic gates. While a standard circuit works with electrical currents, though, the inputs in the biological version are biochemical signals triggered by presence of a protein or pathogen.

Scientists have built and tested a walking robot that can pick up and carry objects but is too small to be seen with the naked eye. The machine is made from DNA, the molecule that carries the'book of life' genetic instructions for all living things. In future, similar nanobots could be used to assemble new chemicals and materials at the molecular level, build incredibly miniaturised circuit boards, or roam through blood vessels delivering medicines. Shown here is a conceptual illustration of a DNA robot sorting two types of cargos. The machine is made from DNA, the molecule that carries the'book of life' genetic instructions for all living things Nanobots are devices made from DNA that are so small they can be injected into the human bloodstream. The nanobot described in the journal was made with a few nucleotides, sub-unit elements of DNA.

Miniature robots with arms and legs made of DNA can sort and deliver molecular cargo, a new study finds. Such DNA robots could be used to shuffle nanoparticles around on circuits, assemble therapeutic compounds, separate molecular components in trash for recycling, or deliver medicines where they need to go in the body, researchers from the California Institute of Technology in Pasadena say. "Just like electromechanical robots have been sent to places that are perhaps too far for humans to go to--for example, on another planet--if we truly master the ways of engineering molecular machines, we would be able to build molecular robots and send them to places that are perhaps too small for humans to go to--for example, inside the bloodstream," says study senior author Lulu Qian, an assistant professor of bioengineering at Caltech. The new robots are made from three basic modules that are each brief snippets of DNA. One module is a "leg" with two "feet" for walking; another is an "arm" with a "hand" for grabbing onto cargo; and the last can recognize specific delivery points and make the hand release its cargo at those spots.

We demonstrate a DNA robot that performs a nanomechanical task substantially more sophisticated than previous work. We developed a simple algorithm and three modular building blocks for a DNA robot that performs autonomous cargo sorting. The robot explores a two-dimensional testing ground on the surface of DNA origami, picks up multiple cargos of two types that are initially at unordered locations, and delivers each type to a specified destination until all cargo molecules are sorted into two distinct piles. The robot is designed to perform a random walk without any energy supply. Exploiting this feature, a single robot can repeatedly sort multiple cargos.