Functionalized Nanowires as Ultrasensitive Sensors – FOcUS

The goal of our project is to develop and disseminate ultrasensitive versatile force sensors based on nanowire or nanotube oscillators probed by optical means.

The exploration of the nanoworld requires advanced tools to measure and understand the myriad of new phenomena that exist at this scale. In this context mechanical oscillators have played a key role, a prominent example being the atomic force microscope (AFM), which allows converting faint forces into measurable signals. Accessing even finer force sensitivities directly promises to bring new insights in nanoscience. Nanomechanical oscillators with their ultralow mass allow extreme force sensitivities, at attoNewton level, even at room temperature, which represents 6 orders of magnitude improvement compared to commercial AFMs. Our aim is to take advantage of the very low effective mass and high mechanical quality factors of nanowires (NWs) to use them as ultrasensitive force sensors. Using rather simple optical detection, we will use nanowire sensors to investigate several fundamental problems in minute force sensing: single electron and photon recoil, extremely weak magnetic near individual spins and optical forces on selected nano-objects.

The particular geometry of NWs and the many different ways they can be functionalized, for example by decorating their apexes with optically active NV centers, opens a large range of applications in force sensing and measurements. Their high aspect ratio allows using these probes in situations inaccessible for integrated solid state sensors. From a more practical point of view, our goal is also to develop measurement systems that are not restricted to cryogenic environments and that can be used by a large community of scientists working in nanoscience.

To reach ultimate sensitivities, the excitation, response and detection of the resonators must be fully understood and these aspects pose interesting scientific problems in their own right. We plan to take advantage of optical forces and force gradients acting on the oscillator to study non linear mechanical effects such as coupling between mechanical modes and self-oscillating regimes. Such studies have clear ramifications in sensors. Experimental developments will be carried out in parallel with detailed numerical simulations based on finite element analysis.
The consortium consists of two complementary partners that have the required competences and infrastructures in all the necessary domains:
P1. ILM-UCBL/CNRS (ILM): Coordination, Nanowire preparation, Mechanical characterization of nanowire, Optical forces measurements, Single electron recoil measurement.
P2. Institut Néel-CNRS (NEEL): Mechanical characterization of nanowire, Optical force characterization and mapping, numerical simulations, spin dependant and magnetic forces.
The pairs ILM-NEEL are already collaborating with a common article already published in Nature Physics. The experience and infrastructure at the two institutes are directly applicable to our FOcUS.
Philippe Poncharal will coordinate the project. He is known for his pioneer work on physical properties of carbon nanotubes with two seminal publications, each exceeding 1000 citations. He also produced several publications in the nanoscience and nano-object field.
Olivier Arcizet will supervise the activity at NEEL. His research interests are cavity-optomechanics at low phonon number, optical frequency comb generation with micro-toroidal cavities and hybrid optomechanical systems. He is an international leader in optomechanics with ~10 related articles published on high impact journal (Nature, Science, etc.).
The project is supported by very encouraging results that have recently been obtained in collaboration between the 2 partners.