Integrated Optomechanical Nanoresonators for Real-Time Single-Molecule Detection Thorugh Photothermal Spectroscopy

Optical absorption microscopy based on the photothermal heating effect has recently succeeded in detecting single molecules with a temperature-sensitive nanomechanical resonator. Molecules are sampled onto the nanomechanical resonator and probed with a free-space laser.

Upon scanning, optical absorption and photothermal heating of the sample results in a detectable detuning in the mechanical resonance frequency. This technique has overcome the main limitations of alternative optical probing methods.

A remaining challenge of nanomechanical photothermal microscopy is the alignment of the free-space optics with the intersecting molecular sample beam necessary to perform time-resolved single-molecule spectroscopy. Furthermore, off-plane optics limits its possibility to be miniaturized.

Integrating NIR/MIR waveguides in nanomechanical resonators will create an innovative optomechanical device that solves the alignment problem, increases the field of view, decreases optical complexity, and enables photothermal spectroscopy miniaturization avoiding absorption spectroscopy limitations (i.e.Fabry-Perot resonances, outcoupling, and propagation losses).

We propose to give the first steps towards a complete integrated photothermal spectroscopic device for single-molecule analysis dispensing with free-space optics.

In the envisioned design, the probing light travels inside the nanomechanical resonator, orthogonal to the sample beam, resulting in an evanescent interaction with the sample molecules on the surface.

This design will enable the detection of single-molecule deposition events from heterogenous samples, in particular, airborne particles and proteins in solution will be the target analyte due to its environmental and health relevance.

Furthermore, the selectivity provided by the spectroscopic measurement allows for identifying and monitoring neoplastic, while the device holds potential use for early diagnostics.