Engineering 101

Sensor detects ever smaller nanoparticles and their movement in space

Although conventional microscopes enlarge images of small structures or objects using light, they miss the mark with nanoparticles that remain invisible due to their inability to absorb or scatter light. Optical resonators can increase the interaction between light and nanoparticles, reflecting light thousands of times between two mirrors. When a nanoparticle is located in the captured light field, it interacts thousands of times with the light so that the change in light intensity is measurable. This allows conclusions to be drawn with respect to the position of the nanoparticle in the three-dimensional space, according to  Dr. Larissa Kohler from KIT’s Physikalisches Institut.

In addition, if a nanoparticle is in water, it collides with water molecules that move in arbitrary directions because of thermal energy. The collisions cause the nanoparticle to move randomly, which can now also be detected.

By using the novel fiber-based Fabry-Pérot resonator, highly reflecting mirrors are located on the ends of glass fibers allowing researchers to derive the thickness of the water surrounding the particle, from its three-dimensional movement. This enables the detection of  to nanoparticles that would have been too small.

A potential application may be the detection of 3-D motion with high temporal resolution and characterization of optical properties of biological nanoparticles, such as proteins, DNA origami, or viruses.

Original Release: Eureka Alert

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