Label-free single molecule detection using microtoroid optical resonators

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Detecting small concentrations of molecules down to the single molecule limit has impact on areas such as early detection of disease, and fundamental studies on the behavior of molecules. Single molecule detection techniques commonly utilize labels such as fluorescent tags or quantum dots, however, labels are not always available, increase cost and complexity, and can perturb the events being studied. Optical resonators have emerged as a promising means to detect single molecules without the use of labels. Currently the smallest particle detected by a non-plasmonically-enhanced bare optical resonator system in solution is a 25 nm polystyrene sphere1. We have developed a technique known as Frequency Locking Optical Whispering Evanescent Resonator (FLOWER) that can surpass this limit and achieve label-free single molecule detection in aqueous solution2. As signal strength scales with particle volume, our work represents a > 100x improvement in the signal to noise ratio (SNR) over the current state of the art. Here the procedures behind FLOWER are presented in an effort to increase its usage in the field.

Original languageEnglish (US)
Article numbere53180
JournalJournal of Visualized Experiments
Issue number106
StatePublished - Dec 29 2015
Externally publishedYes


  • Bioengineering
  • Biological detection
  • Biosensor
  • Frequency locking
  • Issue 106
  • Label-free
  • Microtoroid
  • Optical resonator
  • Single molecule
  • Whispering gallery mode

ASJC Scopus subject areas

  • Neuroscience(all)
  • Chemical Engineering(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)


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