For Better Quantum Sensing, Go With the Flow

The combination of flowing droplets and carefully modulated microwaves lets researchers ignore unwanted background noise and adds to their precision. When it comes to detecting trace amounts of slightly magnetic (or “paramagnetic”) chemicals in small sample volumes, the new flowing nanodiamond approach is already outperforming leading techniques.

(If you’re thinking that science has spared no expense, don’t fear – researchers can analyze hundreds of thousands of droplets for about 63 cents of diamond dust, making it both a relatively inexpensive and effective option.)

Small sensors, big applications

With further development, there are many potential ways to use the nanodiamonds in droplets.

In the new study, a team of researchers headed by UC Berkeley and Berkeley Lab graduate student Adrisha Sarkar and Berkeley Lab postdoc Zack Jones successfully showed they could pick up trace amounts of two paramagnetic species: gadolinium ions and TEMPOL, a stable radical molecule that is sensitive to oxygen.

Several other kinds of paramagnetic ions are of interest, but difficult to study using traditional techniques. Such is the case for reactive oxygen species (ROS), short-lived molecules of oxygen that have been linked to cell metabolism, aging, and stress. The new technique could prove a better way to detect reactive oxygen within single cells, giving experts a way to track cell health, with implications for studying diseases such as cancer. The team is already preparing for such a study.

They’re also looking at how to attach additional components that aid in identification (such as antibodies) to the nanodiamonds, expanding the tool for biological research. One can imagine using the technique to build better diagnostic tests to identify viruses when only trace amounts of the virus are present. Or, because the method is relatively low-tech, Ajoy foresees a portable system that could be used to monitor the air or water for harmful trace contaminants and chemicals, either in the field or in industrial settings. Because the nanodiamond microdroplets are cheap and plentiful, the technique could be scaled up to measure hundreds of different samples with great sensitivity and address complex, real-world problems.

The new approach could also be useful for creating self-driving bioreactors of the future. Bioreactors create controlled environments for growing microorganisms that can make medicines, biofuels, or food ingredients. Because each droplet of nanodiamonds can act as a microscopic “beaker” and can hold a single cell, researchers could potentially use the technique to tune bioreactors.

“You can envision setting up bioreactors in austere environments around the world or in space, to make things like food that you couldn’t deliver on a daily basis,” said Deepti Tanjore, director of the Advanced Biofuels and Bioproducts Process Development Unit at Berkeley Lab. “Having precise quantum sensors that tell you how the microorganism culture is behaving is an important step toward that dream. To build a self-regulating bioreactor, we need that real-time intracellular data.”