Imaging Nanomechanical Vibrations and Manipulating Parametric Mode Coupling via Scanning Microwave Microscopy.

In this study, we present a novel platform based on scanning microwave microscopy for manipulating and detecting tiny vibrations of nanoelectromechanical resonators using a single metallic tip. The tip is placed on the top of a grounded silicon nitride membrane, acting as a movable top gate of the coupled resonator. We demonstrate its ability to map mechanical modes and investigate mechanical damping effects in a capacitive coupling scheme, based on its spatial resolution. We also manipulate the energy transfer coherently between the mode of the scanning tip and the underlying silicon nitride membrane, via parametric coupling. Typical features of optomechanics, such as anti-damping and electromechanically induced transparency, have been observed. Since the microwave optomechanical technology is fully compatible with quantum electronics and very low temperature conditions, it should provide a powerful tool for studying phonon tunnelling between two spatially separated vibrating elements, which could potentially be applied to quantum sensing.

Development of nanomaterial enabling highly sensitive surface-assisted laser desorption/ionization mass spectrometry peptide analysis.

RATIONALE: Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) is an approach derived from matrix-assisted laser desorption/ionization (MALDI)-MS which overcomes the drawbacks associated with the use of organic matrices required to co-crystallize with the analytes. Indeed, nanomaterials commonly used in SALDI-MS as inert surfaces to promote desorption/ionization (D/I) ensure straightforward direct deposition of samples while providing mass spectra with ions only related to the compound of interest. The objective of this study was to develop a novel SALDI-MS approach based on steel plates that are surfaces very rapidly and easily tuned to perform the most efficient peptide detection as possible. To compare the SALDI efficacy of such metal substrates, D/I efficiency and deposit homogeneity were evaluated according to steel plate fabrication processes. METHODS: The studied surfaces were nanostructured steel plates that were chemically modified by perfluorosilane and textured according to different frequencies and laser writing powers. The capacity of each tested 100 surfaces was demonstrated by comparative analyses of a mixture of standard peptides (m/z 600-3000) performed with a MALDI-TOF instrument enabling MALDI, SALDI and imaging experiments. RESULTS: A peptide mix was used to screen the different surfaces depending on their D/I efficiency and their ability to ensure homogeneous deposit of the samples. For that purpose, deposition homogeneity was visualized owing to reconstructed ionic images from all protonated or sodiated ions of the 10 peptides constituting the standard mix. CONCLUSIONS: Seven surfaces were then selected satisfying the required D/I efficiency and deposit homogeneity criteria. Results obtained with these optimal surfaces were then compared with those recorded by MALDI-MS analyses used as references.

Development of a real-time flexible multiphoton microendoscope for label-free imaging in a live animal.

We present a two-photon microendoscope capable of in vivo label-free deep-tissue high-resolution fast imaging through a very long optical fiber. First, an advanced light-pulse spectro-temporal shaping device optimally precompensates for linear and nonlinear distortions occurring during propagation within the endoscopic fiber. This enables the delivery of sub-40-fs duration infrared excitation pulses at the output of 5 meters of fiber. Second, the endoscopic fiber is a custom-made double-clad polarization-maintaining photonic crystal fiber specifically designed to optimize the imaging resolution and the intrinsic luminescence backward collection. Third, a miniaturized fiber-scanner of 2.2 mm outer diameter allows simultaneous second harmonic generation (SHG) and two-photon excited autofluorescence (TPEF) imaging at 8 frames per second. This microendoscope's transverse and axial resolutions amount respectively to 0.8 µm and 12 µm, with a field-of-view as large as 450 µm. This microendoscope's unprecedented capabilities are validated during label-free imaging, ex vivo on various fixed human tissue samples, and in vivo on an anesthetized mouse kidney demonstrating an imaging penetration depth greater than 300 µm below the surface of the organ. The results reported in this manuscript confirm that nonlinear microendoscopy can become a valuable clinical tool for real-time in situ assessment of pathological states.