Advancements in Electronics Technology Bring Free Radicals Detection Closer to Real-Time The ability to detect and analyze free radicals has become increasingly important in various fields, including technology, food quality, and healthcare. These highly reactive molecules can have devastating effects on materials, foods, and biological systems. The technique of electron paramagnetic resonance (EPR) spectroscopy is a crucial tool for detecting and studying free radicals. In recent years, researchers have been working to miniaturize this equipment, enabling scientists to take it into the field.

One of the key challenges in traditional EPR machines is the large size of the powerful electromagnets required to detect and analyze free radicals. However, groups of researchers in California, Germany, and France have been developing ways to shrink these systems onto a chip, allowing for more portable and flexible detection.

The most recent breakthrough comes from a team at the French government technology labs CEA-Leti and CEA-IRIG, in Grenoble. They presented a new, potentially faster, take on chip-scale EPR earlier this year at the IEEE International Solid-State Circuits Conference in San Francisco. This development has significant implications for scientists who want to study free radicals in real-time.

Free Radicals: The Key to Understanding Many Phenomena Free radicals are molecules with unpaired electrons, which makes them highly reactive. These molecules can be present in various environments, including our bodies, materials, and foods. They play a crucial role in many biological processes, but they can also cause damage when present in excess.

“Free radicals determine the quality of almost everything on the planet,” says Jens Anders, director of the Institute of Smart Sensors at the University of Stuttgart, Germany. The presence of free radicals can have significant effects on technology, such as reducing battery capacity or causing photovoltaic panels to age.

EPR Spectroscopy: A Crucial Tool for Analyzing Free Radicals EPR spectroscopy works by detecting the paramagnetic properties of free radicals. When a sample is placed between two poles of an electromagnet, the unpaired electrons in the free radicals align with the magnetic field. A weaker oscillating magnetic field is then applied to the sample, causing the electrons to resonate at specific frequencies.

The EPR spectrometer’s circuitry picks up these resonant frequencies and plots them as a frequency spectrum that chemists can interpret. This information can provide valuable insights into the presence and concentration of free radicals in a sample.

Continuous-Wave Electron Paramagnetic Resonance The CEA-Leti team's chip uses a continuous wave method to detect EPR signals. However, they have developed a new way to measure the phenomenon that is faster than traditional methods. By sweeping very quickly through a range of frequencies, the new circuit can detect micromolar quantities of free radicals in a sample that’s just 10 nanoliters.

This breakthrough relies on injection-locked phase detection, which allows the EPR chip to sweep through its bandwidth in just 200 nanoseconds, equivalent to 1,400 terahertz per second. This is three times as fast as competing systems, according to the researchers.

Pulse Electron Paramagnetic Resonance While the CEA-Leti development advances continuous wave EPR, other researchers have been focusing on chips that do a different form of EPR, called pulse mode. In pulse EPR, instead of presenting free radicals with a sweep of frequencies, they’re exposed to a pulse containing a band of frequencies surrounding the central oscillation frequency.

This approach allows for more flexibility and sensitivity in detecting and analyzing free radicals. At ISSCC 2024, Constantine Sideris and his student Ray Sun at the University of Southern California presented the first chip that can actually perform both continuous wave and pulse EPR.

Turning Free Radicals Detection into a Product The development of miniaturized EPR equipment has required significant advancements in electronics technology. One key challenge was increasing the size of the coil that delivers the varying magnetic field, which had to be segmented and embedded with electronics to prevent radiation.

However, this breakthrough has enabled scientists to create smaller and more efficient EPR chips. The CEA-Leti team plans to let loose its new version of EPR on scientific questions, hoping to reveal new phenomena that were not previously observable due to the speed of the technique.

Conclusion The detection of free radicals is a critical area of research with significant implications for various fields. The advancements in electronics technology have brought us closer to developing miniaturized EPR equipment that can be taken into the field. The CEA-Leti team's breakthrough using injection-locked phase detection has enabled faster and more sensitive detection of free radicals, opening up new possibilities for scientific research.

As researchers continue to push the boundaries of EPR technology, we can expect significant advancements in our understanding of free radicals and their role in various environments.

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