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       Device made from glass microbeads could provide 100 times more computing power than other DNA computers
       A DNA computer that displays results by moving tiny beads could greatly enhance the parallel computing capabilities of such machines.
       DNA computers take up less space than silicon-based computers and can operate in humid environments. They can be used in applications such as detecting contaminants in drinking water or monitoring sugar levels in the body.
       Previous designs used fluorescent tags to display results and could only display dozens of results at a time. They also need sophisticated microscopes to read the results.
       “A conservative estimate is that we can perform a hundred times more parallel computations with DNA computers than with computers using fluorescent markers,” said Khalid Salaita of Emory University in Atlanta, Georgia.
       Salaita and his colleagues built a computer using DNA-coated glass beads that rolled or stopped on the surface of a gold chip, depending on how the DNA strands interacted with molecules attached to the chip’s surface. Rotating is equivalent to pin 1, and stopping is equivalent to pin 0.
       The results of the calculations can be discovered by tracking the movement of the beads using a smartphone camera attached to a simple magnifying glass.
       “It’s really crazy. You can use a standard smartphone to translate information from the computational operation of DNA into the macroscopic world in just 15 minutes,” Salaita said.
       The team designed “targeting” DNA molecules onto the beads that could bind to corresponding RNA molecules attached to the surface of the chip. When this happens, the beads remain stationary in their original position, but when the enzyme ribonuclease H is added to the chip, the beads roll around, breaking up the DNA-RNA complexes.
       The researchers then added a DNA “lock complex” to the computer, which allowed them to control the movement of the balls depending on the presence or absence of certain DNA molecules. They demonstrated that the presence of DNA molecules stopped the balls, while their absence caused the balls to roll. The system can be easily adapted to detect any DNA of interest in the environment.
       Because there are thousands of microbeads of different shapes and sizes, the researchers say the computer can produce thousands of readings in parallel. They hope the device will provide a quick way to determine the level of virus in saliva. “What’s really neat is that you can use multiple parallel operations to determine whether you have SARS-CoV-2 and also determine whether you have influenza A and other pathogens,” Salaita said.
       However, further work is needed to find ways to replenish the RNA molecules on the surface of the chip, which degrade after 24 hours and limit the life of the computer.
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