Reviewed by Lexie CornerMar 6 2025
Researchers at Berkeley Lab have used nanodiamonds in liquid microdroplets for quantum sensing. This new method is particularly useful for studying individual cells or trace chemicals because it is sensitive, fast, precise, and requires only small amounts of the material being studied. The study was published in Science Advances.
Researchers developed a method to detect small amounts of certain chemicals by adding nanodiamonds to microdroplets. Image Credit: Ajoy Lab/UC Berkeley
To improve quantum sensing, researchers combined a standard green laser, microwaves with energy similar to Wi-Fi, and diamond dust in tiny water droplets. This combination created a precise tool for chemical detection.
We weren’t even sure whether our technique would work, but it turned out to be surprisingly easy and effective. There are broad applications where these sensors could be deployed into interesting environments and help you find something that would usually be hard to detect.
Ashok Ajoy, Faculty Scientist, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Department of Energy
Quantum sensing takes advantage of unique properties that emerge at the smallest scales. In this method, researchers created microdroplets, millions of times smaller than a raindrop. These droplets contain a special type of diamond where nitrogen atoms are added and carbon atoms removed, creating "nitrogen vacancies" that act as quantum sensors. When these droplets pass in front of a laser and are hit by microwaves, the nanodiamonds emit light. The amount of light emitted in the presence of a microwave field correlates to the surrounding materials, allowing researchers to determine if a chemical of interest is nearby.
By combining flowing droplets with carefully modulated microwaves, the researchers can ignore unwanted background noise and increase precision. This new flowing nanodiamond technique is already outperforming existing methods for detecting trace amounts of slightly magnetic (or "paramagnetic") chemicals in small sample volumes.
Additionally, researchers can analyze hundreds of thousands of droplets for just 63 cents of diamond dust, making this method both cost-effective and efficient.
Small Sensors, Big Applications
With further development, nanodiamonds in droplets could have a wide range of potential applications.
A team led by graduate student Adrisha Sarkar of UC Berkeley and Berkeley Lab, along with postdoc Zack Jones of Berkeley Lab, demonstrated in their recent study that they could detect traces of two paramagnetic species: gadolinium ions and TEMPOL, a stable radical molecule that is oxygen-sensitive.
Researchers are also interested in other types of paramagnetic ions, which are difficult to study using conventional methods. This includes short-lived oxygen molecules called reactive oxygen species (ROS), which are associated with stress, aging, and cell metabolism.
This new method could offer a more effective way of detecting reactive oxygen within individual cells, providing a valuable tool for monitoring cell health. With implications for diseases like cancer, the research team is preparing to explore this potential.
Additionally, the team is exploring the possibility of attaching other elements, such as antibodies, to the nanodiamonds to expand the scope of biological research. This approach could lead to more accurate diagnostic tests to detect viruses in situations where the virus is present in very small quantities.
Ajoy envisions a portable system that could be used in industrial or field settings to monitor the air or water for hazardous chemicals and trace contaminants. Due to the low-tech nature of the method, it could be scaled up to measure hundreds of samples with high sensitivity, addressing real-world challenges at a low cost.
The technique may also contribute to the development of self-driving bioreactors. These bioreactors, used to grow microorganisms that can produce food ingredients, biofuels, or medications, could be optimized with this method. Each nanodiamond droplet could function as a tiny "beaker," containing a single cell, allowing for precise tuning of bioreactor conditions.
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. 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.
Deepti Tanjore, Director, Advanced Biofuels and Bioproducts Process Development Unit, Lawrence Berkeley National Laboratory
The Berkeley Lab's Laboratory-Directed Research and Development (LDRD) program, which supports innovative research and experimentation, provided funding for the nanodiamond droplet study. Experts from chemistry, microfluidics, biosciences, and earth sciences collaborated on the project.
Flowing Microdroplets
In this slowed-down video, microdroplets filled with nanodiamonds flow through different structures in the science team’s device. The droplets are generated and spaced out. Their contents mix as they travel through loops until they are deposited in a storage chamber. Video Credit: Courtesy of Ajoy Lab/UC Berkeley
Journal Reference:
Sarkar, A., et al. (2025) High-precision chemical quantum sensing in flowing monodisperse microdroplets. Science Advances. doi.org/10.1126/sciadv.adp4033