Photonic Sensor for High-Speed Biodetection

A fluid meniscus inside an opto-mechano-fluidic resonator (OMFR) made of high purity silica glass. Particles flowing through the internal micro channel can be detected optically at extremely high speed. (Source: U Illinois)

A fluid meniscus inside an opto-mechano-fluidic resonator (OMFR) made of high purity silica glass. Particles flowing through the internal micro channel can be detected optically at extremely high speed. (Source: U Illinois)

Researchers from the Univer­sity of Illinois at Urbana-Champaign have developed a new technique for extremely high speed photonic sensing of the mechanical properties of freely flowing particles using an opto-mechano-fluidic reso­nator (OMFR). This research poten­tially opens up completely new mechanical axes of measure­ment on micro-, nano-, and bio­particles.

“It is known that diseases such as cancers and anemia can correlate with mechanical properties of cells such as compressi­bility and visco­elasticity, but these properties are not used diagnostically due to absence of tools with enough speed and sensitivity to perform the measurement,” explained Gaurav Bahl, an assistant professor of mechanical science and engineering at Illinois. “Because of this, we have a substantial knowledge-gap, and have barely scratched the surface of under­standing of how diseases modify the mechanical properties of cells in our body. Developing knowledge around the mechanics of cells and bio­particles can help us understand the mobility of these micro-objects throughout the human body, about how tumors form, about how cells and bacteria can propagate through us, how diseases spread, and more.”

High-speed optical detection methods, such as flow cytometry, are routinely used for analysis of large popu­lations of particles through measurements of their optical properties, with analysis speeds approaching 50,000 particles per second. Optical sensors, however, cannot directly measure any mechanical properties of the particles such as mass, density, compressi­bility, stiffness. Until now, mechanical sensors have not approached the speed of optical flow cytometers, which makes routine measure­ments on large cell populations simply impractical.

“In this study, we aimed to blend the best features of optical sensing, i.e. the extremely high bandwidth and sensi­tivity, with mechanical sensing which gives us the ability to measure mechanical properties,” stated doctoral candidate Kewen Han. “To achieve this, we have developed a new microfluidic opto-mechanical device that optically detects the mechanical pertur­bations created by individual micro­particles flowing through the fluidic channel at very high speed.”

Using bakers’ yeast and two types of microbeads, the researchers explored the particle-sensing capabilities of the OMFR. “The OMFR’s multimode sensing capa­bility permits measurement of multiple particles with redundancy, and indicates future potential for inertial imaging,” Han said. “The system also detects mechanical energy loss associated with individual particles, likely related to visco­elastic properties of the soft material and boundary loss at interface of particle and liquid.”

“We have shown that our technique is sensitive to the density and compressi­bility of each individual particle as it passes by,” Bahl added. “The smallest detec­table particle as reported in this work is around 660 nm. This work presents a new approach to perform resonantly enhanced optical sensing of freely flowing particles through the action of long-range phonons that extend between solid and fluid phases of the sensor and sample.” (Source: U Illinois)

Reference: K. Han et al.: High-throughput sensing of freely flowing particles with optomechanofluidics, Optica 3, 585 (2016); DOI: 10.1364/OPTICA.3.000585

Link: Dept. of Mechanical Science and Engineering (G. Bahl), University of Illinois at Urbana-Champaign, USA

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