Scientists tune into cells’ electrical whispers with atom-thick “microphones”

For decades, probing the electrical activity of living cells has been like listening to a symphony recorded with bulky, imprecise microphones — relying on invasive electrodes and sometimes disruptive dyes. Now, engineers at the University of California, San Diego, have unveiled a potentially life-changing invention: atom-thick semiconductors that can “hear” these faint cellular signals using only light, offering a less invasive and potentially much more detailed listening experience.

A new study published in Nature Photonics details how ultra-thin materials, barely thicker than a single atom, can act as highly sensitive detectors of biological electrical activity. These quantum materials, which confine electrons to two dimensions, respond to electrical fields by subtly shifting their interaction with light. This allows researchers to map cellular voltage changes with unprecedented speed and resolution — all without physically touching the cell or introducing foreign chemicals.

Scientists have long sought better ways to observe the electrical conversations of the body’s most excitable cells: neurons, heart muscle fibers, and pancreatic cells. These tiny electrical pulses orchestrate everything from thought to heartbeat and are fundamental to life. However, current methods have significant limitations.

Traditional electrophysiology uses fine microelectrodes to provide precise recordings but is inherently limited in scale. “Implanting electrodes across large tissue regions can cause significant damage, and even the most advanced probes are limited to recording just a few hundred channels at once,” the researchers note. While optical techniques like calcium imaging offer broader views, they only provide an indirect picture. Instead of recording the voltage shifts driving cellular communication, they capture secondary changes that can introduce significant discrepancies,” the study explains.

The UC San Diego team, led by Professor Ertugrul Cubukcu, proposes a high-speed, all-optical alternative. “We believe that the voltage sensitivity of excitons in monolayer semiconductors has the potential to enable high spatiotemporal investigation of the brain’s circuitry,” said Cubukcu, a professor in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering, as well as the Department of Electrical and Computer Engineering at the UC San Diego Jacobs School of Engineering.

Their method exploits the quantum dance of electrons within these materials. When exposed to an electric field, electrons in the atom-thick semiconductor molybdenum sulfide shift between electrically neutral excitons and charged trions. Crucially, the researchers discovered this exciton-to-trion conversion could be harnessed to sense the electrical signals of living cells directly.

“In other words, the quantum properties of the material itself can be used as a sensor,” the researchers state. By tracking subtle changes in the material’s photoluminescence – the light it emits – they could map the electrical activity of heart muscle cells in real time at speeds unmatched by conventional imaging.

The team chose molybdenum sulfide for its biocompatibility and unique property: it naturally develops sulfur “vacancies” during production, creating a high density of trions. “This built-in defect makes it exceptionally responsive to changes in nearby electric fields, including the ones generated by living cells, allowing spontaneous exciton-to-trion conversion,” the researchers explained.

While this all-optical method holds significant promise, researchers acknowledge that it is still an early-stage technology. Potential limitations include the material’s sensitivity to environmental factors, the depth of light penetration in tissue, and the complexities of translating lab experiments into practical, widely accessible tools. Further research will be necessary to optimize the material’s production, enhance signal clarity, and fully explore its long-term biocompatibility.

However, the potential impact is noteworthy. This technology could transform our understanding of neurological and cardiac disorders, enhance brain stimulation therapies, and provide a non-invasive, high-speed insight into the electrical language of life itself. As Cubukcu suggests, this quantum approach may indeed pave the way for a “high spatiotemporal investigation of the brain’s circuitry” and beyond, leading us into a new era of cellular electrophysiology.