The newly-developed all-optical nanosensors are luminescent nanocrystals that can change intensity and/or color when you push or pull on them; they are probed with light only and therefore allow for fully remote read-outs — no wires or connections are needed; they have 100 times better force sensitivity than the existing nanoparticles that utilize rare-earth ions for their optical response, and an operational range that spans more than four orders of magnitude in force, a much larger range (10-100 times larger) than any previous optical nanosensor.
Illustration of the atomic arrangement within a single lanthanide-doped nanocrystal; each lanthanide ion can emit light. Image credit: Andrew Mueller / Columbia Engineering.
“We expect our discovery will revolutionize the sensitivities and dynamic range achievable with optical force sensors, and will immediately disrupt technologies in areas from robotics to cellular biophysics and medicine to space travel,” said Dr. Jim Schuck, a researcher at Columbia University.
The new nanosensors achieve high-resolution, multiscale function with the same nanosensor for the first time.
This is important as it means that just this nanosensor, rather than a suite of different classes of sensors, can be employed for the continuous study of forces, from the subcellular to the whole-system level in engineered and biological systems, such as developing embryos, migrating cells, batteries, or integrated NEMS, very sensitive nanoelectromechanical systems in which the physical motion of a nanometer-scale structure is controlled by an electronic circuit, or vice versa.
“What makes these force sensors unique — apart from their unparalleled multiscale sensing capabilities — is that they operate with benign, biocompatible, and deeply penetrating infrared light,” said Dr. Natalie Fardian-Melamed, a postdoctoral researcher at Columbia University
“This allows one to peer deep into various technological and physiological systems, and monitor their health from afar.”
“Enabling the early detection of malfunction or failure in these systems, these sensors will have a profound impact on fields ranging from human health to energy and sustainability.”
The researchers were able to build these nanosensors by exploiting the photon-avalanching effect within nanocrystals.
In photon-avalanching nanoparticles, the absorption of a single photon within a material sets off a chain reaction of events that ultimately leads to the emission of many photons. So, one photon is absorbed, many photons are emitted.
The optically active components within the study’s nanocrystals are atomic ions from the lanthanide row of elements in the periodic table, also known as rare-earth elements, which are doped into the nanocrystal; for this study, the scientists used thulium.
They found that the photon avalanching process is very, very sensitive to several things, including the spacing between lanthanide ions.
With this in mind, they tapped on some of their photon avalanching nanoparticles (ANPs) with an atomic force microscopy (AFM) tip, and discovered that the avalanching behavior was greatly impacted by these gentle forces — much more than they had ever expected.
“We discovered this almost by accident,” Dr. Schuck said.
“We suspected these nanoparticles were sensitive to force, so we measured their emission while tapping on them.”
“And they turned out to be way more sensitive than anticipated!”
“We actually didn’t believe it at first; we thought the tip may be having a different effect.”
Knowing how sensitive the ANPs were, the authors then designed new nanoparticles that would respond to forces in different ways.
In one new design, the nanoparticle changes the color of its luminescence depending on the applied force.
In another design, they made nanoparticles that do not demonstrate photon avalanching under ambient conditions, but do begin to avalanche as force is applied — these have turned out to be extremely sensitive to force.
They now aim to apply these force sensors to an important system where they can achieve significant impact.
“The importance of developing new force sensors was recently underscored by Ardem Patapoutian, the 2021 Nobel Laureate who emphasized the difficulty in probing environmentally sensitive processes within multiscale systems — that is to say, in most physical and biological processes,” Dr. Schuck said.
“We are excited to be part of these discoveries that transform the paradigm of sensing, allowing one to sensitively and dynamically map critical changes in forces and pressures in real-world environments that are currently unreachable with today’s technologies.
The team’s work appears today in the journal Nature.
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Natalie Fardian-Melamed et al. 2025. Infrared nanosensors of piconewton to micronewton forces. Nature, in press; doi: 10.1038/s41586-024-08221-2
This article is a version of a press-release provided by Columbia University.