Fast, Label-Free Tracking of Single Viruses and Weakly Scattering Nanoparticles in a Nanofluidic Optical Fiber

Sanli Faez, Yoav Lahini, Stefan Weidlich, Rees F. Garmann, Katrin Wondraczek, Matthias Zeisberger, Markus A. Schmidt, Michel Orrit, Vinothan N. Manoharan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

109 Scopus citations


High-speed tracking of single particles is a gateway to understanding physical, chemical, and biological processes at the nanoscale. It is also a major experimental challenge, particularly for small, nanometer-scale particles. Although methods such as confocal or fluorescence microscopy offer both high spatial resolution and high signal-to-background ratios, the fluorescence emission lifetime limits the measurement speed, while photobleaching and thermal diffusion limit the duration of measurements. Here we present a tracking method based on elastic light scattering that enables long-duration measurements of nanoparticle dynamics at rates of thousands of frames per second. We contain the particles within a single-mode silica fiber having a subwavelength, nanofluidic channel and illuminate them using the fiber's strongly confined optical mode. The diffusing particles in this cylindrical geometry are continuously illuminated inside the collection focal plane. We show that the method can track unlabeled dielectric particles as small as 20 nm as well as individual cowpea chlorotic mottle virus (CCMV) virions - 26 nm in size and 4.6 megadaltons in mass - at rates of over 3 kHz for durations of tens of seconds. Our setup is easily incorporated into common optical microscopes and extends their detection range to nanometer-scale particles and macromolecules. The ease-of-use and performance of this technique support its potential for widespread applications in medical diagnostics and micro total analysis systems.

Original languageEnglish
Pages (from-to)12349-12357
Number of pages9
JournalACS Nano
Issue number12
StatePublished - 27 Oct 2015
Externally publishedYes


FundersFunder number
Center for Nanoscale SystemsCNS
National Nanotechnology Infrastructure Network
National Science Foundation1420570
National Sleep FoundationPHY-1066293
Massachusetts Institute of Technology
Harvard University
Aspen Center for Physics
Materials Research Science and Engineering Center, Harvard UniversityDMR-1420570


    • biosensing
    • label-free
    • nanofluidics
    • self-diffusion
    • single particle tracking
    • virus detection


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