Johns Hopkins Applied Physics Laboratory scientists are developing a quantum sensing platform roughly the size of a laptop, aiming to bring the versatility of nuclear magnetic resonance (NMR) spectroscopy to warfighters in contested environments. Current NMR techniques, while capable of identifying both chemical and biological threats, rely on refrigerator-sized equipment and large liquid samples; the APL team seeks to overcome these limitations with a portable device.
“There are many good sensors employed in field environments, but they tend to focus on a narrow range of either chemical or biological threats — not both,” said APL experimental physicist Isaiah Gray. This new platform promises to detect a wider spectrum of harmful substances, potentially revolutionizing safety for those operating in high-risk areas.
Nano-Container Design Improves Threat Detection Sensitivity
These containers are designed to confine nuclear spins, a critical step toward achieving the sensitivity needed to identify minute quantities of harmful substances, potentially increasing NMR accuracy by an order of magnitude according to simulations conducted. This improvement addresses a key limitation of conventional NMR, which requires large sample volumes and bulky, cryogenically cooled equipment for sufficient signal strength. The core innovation lies in manipulating the quantum property of nuclear spin; when exposed to magnetic fields, these spins emit spectral data revealing molecular structure, allowing differentiation between benign and dangerous compounds.
While nitrogen-vacancy (NV) centers in diamonds offer a pathway to miniaturizing NMR, extracting reliable signals from extremely small samples has proven difficult. Confining the nuclear spins within these newly designed nano-containers is intended to extend the duration of the signal, enabling accurate readings even with volumes measured in tens or hundreds of atoms.
This approach circumvents the need for large sample sizes traditionally associated with NMR analysis. The development of these nano-containers is not merely a theoretical exercise; the team has already constructed a working prototype capable of measuring magnetic fields by reading the spin states of the NV centers. Currently, the focus is on achieving the necessary resolution to reliably identify chemicals within these minuscule samples.
Researchers have simulated various container geometries, identifying one configuration that demonstrates the potential to meet the required sensitivity thresholds, and are now actively engaged in the fabrication process. “In the field, you don’t need to achieve the level of accuracy that you do in a chemistry lab,” said Isaiah Gray, an experimental physicist at APL. “You just need to be able to answer a couple of critical questions: Is the substance a threat?
Do you need to be wearing standard personal protective equipment or a hazmat suit? We think that’s achievable with a device that could fit in a backpack.” This targeted approach to accuracy, sufficient for field assessment rather than laboratory-grade analysis, is central to the platform’s design philosophy.
The APL platform aims to overcome this limitation by using the broad applicability of NMR spectroscopy, which can identify a wide spectrum of harmful substances. The team’s internal funding has facilitated the construction of a proof-of-concept demonstration and the initial steps toward prototyping a fieldable NMR device capable of detecting both biological and chemical threats in small volumes. The potential applications extend far beyond warfighter safety, however. NV-driven quantum magnetometers, the foundation of this technology, have implications for environmental monitoring, GPS-denied navigation through local magnetic field mapping, and even low-frequency radio communications.
Gray highlighted the versatility of the platform, noting ongoing discussions with colleagues about potential deployments on satellites or within cryostats. “We’ve already had several conversations with colleagues across the Lab about different applications—can the sensor be placed on a satellite? Or inside a cryostat?” he said. “The answer is generally ‘yes.’” Sarah Adams, program manager for Alternative Computing Paradigms in APL’s Research and Exploratory Development Mission Area, emphasized the strong combination of expertise driving this project.
“The better we get at building these, the more we can integrate them in creative ways to address all kinds of mission-specific challenges,” Adams said. “Creating this capability requires the ability to not only conceptualize it but to then execute and integrate all the disparate pieces—quantum sensing, microfluidics, the physics and chemistry of NMR, and microfabrication.
The Laboratory has the multidisciplinary expertise to combine all of these to demonstrate a critical advancement in bio-chem threat detection.” The team, comprised of Andrew Bennett-Jackson, David Flay, Prashant Ramesh, Bryan Brensinger, and Andrea Timm alongside Gray, is currently focused on fabricating the nano-container structures and validating their performance.
Successful implementation of this technology promises a significant leap forward in portable threat detection, offering a versatile and sensitive platform for safeguarding personnel in a variety of challenging environments. The ability to rapidly and accurately identify a broad range of chemical and biological agents, even in minute quantities, could revolutionize safety protocols for warfighters, first responders, and environmental monitoring agencies alike.
There are many good sensors employed in field environments, but they tend to focus on a narrow range of either chemical or biological threats – not both.
Isaiah Gray, experimental physicist at APL
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