Physicists suggest new way to measure speed in liquid micro-flows

October 11, 2018, ITMO University

Scientists from ITMO University developed a novel optical method of measuring reagent delivery rates for "labs on a chip." The method is based on a dynamic interaction between a nanoantenna and luminescent molecules as the distance between them affects light intensity. Processed mathematically, these light dynamics determine the flow speed. This method can also be used for measuring temperature and identifying flow types. The research was published in Laser & Photonics Reviews.

"Lab on a chip" is a tiny device that conducts chemical reactions, analysis or synthesis on a chip measuring only several square centimeters. It can be used for estimating concentrations of substances, carrying out diagnostics, or performing complex biochemical processes. Reagents are delivered via micron-diameter microtubules. The delivery rate affects the course of the reaction, so scientists are developing special sensors to monitor this variable.

ITMO University scientists developed a novel optical for measuring the speed of liquid micro-flows. It is based on the Purcell Effect, which appears when luminescent interact with a concentrating electromagnetic field. The effect describes the impact the distance to nanoantenna has on the luminescence of excited molecules. Monitoring how a solution containing luminescent molecules changes its radiation when moving past the nanoantenna helps determine its speed.

"Luminescent molecules emit light when excited by a laser pulse. However, the duration of this emission may vary depending on how far they are from the nanoantenna. We run a luminescent-molecule solution past the nanoantenna, irradiate the region near the nanoantenna with a short laser pulse, and record how the signal fades. After special processing, the analysis of how the signal fades in time allows us to understand how quickly the solution was moving," explains Alexey Kadochkin, research associate at ITMO University's International Laboratory of Nano-opto-mechanics.

Post-processing of the received fading signal helps scientists select components with different fading rates. The most intense component corresponds to radiation the solution emits when located farthest from the nanoantenna. At the same time, the fading rates spectrum contains components that correspond to the emission of molecules interacting with the nanoantenna. Establishing the position of these components helps measure the flow speed.

"This work still remains in the realm of theoretical, so we are really proud of the fact that it made the front cover. In the near future we plan to extend the method for measuring temperatures by recording the Brownian motion, learn how to distinguish between different flow types, and conduct experiments. As a result, we want to design a conclusive model for "lab on a chip" sensors," says Alexander Shalin, head of ITMO University's International Laboratory of Nano-opto-mechanics.

Explore further: Nanodiamond turns into controllable light source

More information: Alexey S. Kadochkin et al. Quantum Sensing of Motion in Colloids via Time-Dependent Purcell Effect, Laser & Photonics Reviews (2018). DOI: 10.1002/lpor.201800042

Related Stories

Nanodiamond turns into controllable light source

May 2, 2018

A research group from ITMO University has developed a controlled light source based on nanodiamond. Experiments have shown that the diamond shell doubles the emission speed light sources and helps to control them without ...

Researchers invent light-emitting nanoantennas

February 19, 2018

Scientists from ITMO University have developed effective nanoscale light sources based on halide perovskite. Such nanosources are based on subwavelength nanoparticles serving both as emitters and nanoantennas and allow enhancing ...

Recommended for you

CMS gets first result using largest-ever LHC data sample

February 15, 2019

Just under three months after the final proton–proton collisions from the Large Hadron Collider (LHC)'s second run (Run 2), the CMS collaboration has submitted its first paper based on the full LHC dataset collected in ...

Gravitational waves will settle cosmic conundrum

February 14, 2019

Measurements of gravitational waves from approximately 50 binary neutron stars over the next decade will definitively resolve an intense debate about how quickly our universe is expanding, according to findings from an international ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.