DNA Robot Sorts Molecules Autonomously The Engineer posted on September 15, 2017

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Such a useful helper at the moment may be in the science fiction realm; however Caltech researchers have managed to develop an autonomous molecular machine that can perform similar operations-at the nanoscale.

On the future outlook of research and development in the field of nanotechnology, co-researcher Qian said: "The biggest implication that I hope the work will have is to inspire more researchers to develop modular, collective, and adaptive DNA robots for a diverse range of tasks, to truly understand the engineering principles for building artificial molecular machines, and make them as easily programmable as macroscopic robots". The robots have been programmed to find and collect fluorescent molecules out of the DNA based platform. Considerable artistic license has been taken.

Lulu Qian, assistant professor of bioengineering, and her team at the California Institute of Technology have created a microscopic machine from DNA that is able to independently perform multiple tasks.

A (very) conceptual illustration of two DNA robots collectively performing a cargo-sorting task on a DNA "origami" surface.

The nanobot, described in the journal Science, was constructed from three basic building blocks to provide "feet" for walking, an "arm" and "hand" for picking up objects, and a segment that can recognise a specific drop-off point and trigger the release of the cargo.

Each of these components is made of just a few nucleotides within a single strand of DNA.

In tests the nanobot was sent to explore a molecular surface, pick up two different fluorescent dye molecules coloured yellow and pink, and deposit them at specific target drop-off points. The robot effectively sorted six scattered molecules, three yellow and three pink, into their correct places in 24 hours.

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"We designed specific drop‐off locations for each type of cargo: If the type matches, the drop‐off location will signal the robot to release the cargo; otherwise the robot will continue to walk around and search for another drop‐off location", explained Qian. It's also programed like a robot, although in this case the programing is all done in the language of chemicals.

There are now three emerging fields within DNA nanoscience, the science of creating molecular-sized devices out of DNA: The self-assembly of nanostructures from DNA strands; molecular computation and data storage; and DNA robotics, which is the focus of the study published this week in Science.

DNA is composed of the nucleotides adenine (A), thymine (T), cytosine (C) and guanine (G).

A single strand possessing the right nucleotides can push two partially zipped strands to unzip from each other. The robot moves by attaching to one peg after another, and linking to its DNA. Furthermore, the length of a single strand or two zipped strands can be measured.

Using these physical and chemical principles, the researchers can create not only robots but also "playgrounds", such as molecular pegboards, to analyze them on.

While the DNA strand isn't a robot in the electromechanical sense, it's designed and built much in the same manner as a traditional robot, with moving parts that stand in for legs, arms, and hands. As one foot lands, the other lifts up, causing it to randomly move from stone to stone until it eventually comes into contact with the desired cargo.

It may take a day for a robot to travel the whole board. (A sheet of paper, by comparison, is about 100,000 nanometers thick.) As the robots roam the pegboard, they grab molecules tethered to the pegs, then drop them off when they receive a chemical signature at a different peg. The process is slow, but it allows for an extremely simple robot design that utilizes very small quantities of chemical energy.