Cavity optomechanical spring sensing of single molecules

Abstract

Label-free bio-sensing is a critical functionality underlying a variety of health- and security-related applications. Micro-/nano-photonic devices are well suited for this purpose and have emerged as promising platforms in recent years. Here we propose and demonstrate an approach that utilizes the optical spring effect in a high-Q coherent optomechanical oscillator to dramatically enhance the sensing resolution by orders of magnitude compared with conventional approaches, allowing us to detect single bovine serum albumin proteins with a molecular weight of 66 kDa at a signal-to-noise ratio of 16.8. The unique optical spring sensing approach opens up a distinctive avenue that not only enables biomolecule sensing and recognition at individual level, but is also of great promise for broad physical sensing applications that rely on sensitive detection of optical cavity resonance shift to probe external physical parameters.

Single Nanoparticle Detection Using Optical Microcavities

“…[51] A microfluidic system may also need to be built in order to detect the analyte in an aqueous environment. [159] Copyright 2016, Nature Publishing Group. Single molecule detection.…”

“…Using plasmonic enhancement, individual thyroglobulin and BSA protein molecules, with masses of 1 ag and 0.11 ag (66 kDa), respectively, have been detected experimentally (Figure 17a). [159] In this optical spring sensing proposal, the detectable sensing signal is improved and is dependent on both the effective mechanical Q and load optic Q of the cavity. [41] Using the mode locking technique, an individual human interleukin-2 molecule with a mass of 15.5 kDa was detected (Figure 17d).…”

“…[135] By embedding a PhC microcavity inside a microfluidic channel, binding events of single streptavidin molecules with a mass of 53 kDa were observed (Figure 17b). [159] Without any plasmonic enhancement or mode locking technique, the optomechanical sensing method realizes the detection of single BSA molecules at an SNR of 16.8 (Figure 17f). [52] The detection limit has been pushed down to a mass of ≈2350 Da by measuring the nucleic acid hybridization of a single 8-mer oligonucleotides using plasmonic enhancement (Figure 17c).…”

Advances in optoplasmonic sensors – combining optical nano/microcavities and photonic crystals with plasmonic nanostructures and nanoparticles

“…In the same vein as WGM lineshape monitoring, the shifts in the mechanical resonance frequency can alternatively be extracted and analysed. A linewidth of 0.1 Hz centred at a frequency of 262 kHz, equating to a mechanical quality factor of 2.6 × 10 6 , with higher-order harmonics, has been reported by Yu et al and then employed as to detect proteins with masses of 66 kDa [96] (Figure 9). Such acoustic modes can be read out from cavities in liquid phase under ambient conditions as well [97] (Figure 10), opening the way for significant optomechanical interactions that lie between optical and mechanical degrees of freedom.…”

Label-Free Biological and Chemical Sensing Using Whispering Gallery Mode Optical Resonators: Past, Present, and Future

“…These include split-frequency sensing [83,84,85,86], resonance broadening [87], and optomechanical oscillations [88,89]. Split frequency sensing is when resonance doublets occur due to backscattering within the cavity from, for example, a manufacturing defect.…”