L'étude des systèmes non-linéaires ouvre un large champ d'investigation en recherche fondamentale, dans cette optique les Systèmes Nano-Electro-Mécanique (NEMS) sont des outils de premier choix. Ce manuscrit met en avant l'utilisation des propriétés non-linéaires de nano-résonateurs pour la physique fondamentale. À la suite d'une calibration rigoureuse de notre dispositif expérimental, nous avons caractérisé les principaux paramètres associés à la résonance de nos structures avec, en particulier, la non-linéarité de Duffing qui est à la source des mécanismes de couplage entre les différents modes de notre système. Une nouvelle procédure expérimentale utilisant une excitation à deux tons est présentée, émergeant du couplage entre modes mais en stimulant un seul mode résonant : un système de détection à haute précision de la résonance de la structure. Le régime de Duffing engendre également l'ouverture d'une hystérésis au sein de la courbe de résonance du NEMS, configuration qui est alors utilisée comme système modèle pour le phénomène de bifurcation. Nous démontrons, numériquement et expérimentalement, que le comportement non-linéaire et les lois de puissances universelles décrites par la théorie sont valides au-delà des prédictions attendues. Différentes techniques expérimentales sont finalement présentées, utilisant les NEMS afin de détecter des caractéristiques fondamentales de la matière condensée, comme les signatures des systèmes à deux niveaux présents au sein des nano-résonateurs ou les propriétés de glissement dans un gaz raréfié. / The investigation of non-linear dynamics intrinsically opens access to a broad field of researches, and Nano-Electro-Mechanical Systems (NEMS) are valuable tools for this purpose. In the present manuscript, we emphasize the fundamental applications of non-linear nano-resonators for condensed matter. After a careful calibration of our peculiar experimental set-up, we characterize the relevant parameters associated to the resonance of our devices, notably the Duffing non-linearity which is the essence of coupling mechanisms between distinct modes of the system. We present a new scheme emerging from the mode-coupling technique, using a two-tone drive but actuating a single flexural mode: a high precision detection procedure of the initial resonator's response. The Duffing regime also opens an hysteresis within the resonance line of the NEMS, and the device is then employed as a model system for the associated bifurcation process. We explored numerically and experimentally this physical phenomenon and found that both the non-linear behaviour and the universal power laws described in the general theory are still valid far beyond any analytical predictions. We finally describe different techniques using NEMS as sensors to measure fundamental features of condensed matter physics, like signatures of two level systems within the resonator's material or slippage in a rarefied gas.

Three problems are investigated in the context of quantum collective dynamics. First, we examine the optomechanics of a Bose-Einstein condensate trapped in an optical ring cavity and coupled to counter-propagating light fields. Virtual dipole transitions cause the light to recoil elastically from the condensate and to excite its atoms into momentum side modes. These momentum side modes produce collective density oscillations. We contrast the situation to a condensate trapped in a Fabry-Perot cavity, where only symmetric ("cosine") side modes are excited. In the ring cavity case, antisymmetric ("sine") modes can be excited also. We explore the mean field limit and find that even when the counter-propagating light fields are symmetrically pumped, there are parameter regions where spontaneous symmetry breaking occurs and the sine mode becomes occupied. In addition, quantum fluctuations are taken into account and shown to be particularly significant for parameter values near bifurcations of the mean field dynamics. The next system studied is a hybrid composed of a high quality micromechanical membrane coupled magnetically to a spinor condensate. This coupling entangles the membrane and the condensate and can produce position superposition states of the membrane. Successive spin measurements of the condensate can put the membrane into an increasingly complicated state. It is possible in principle to produce nonclassical states of the membrane. We also examine a model of weaker, nonprojective measurements of the condensate's spin using phase contrast imaging. We find an upper limit on how quickly such measurements can be made without severely disrupting the unitary dynamics. The third situation analyzed is the string breaking mechanism in ultrahigh energy collisions. When quark-antiquark pairs are produced in a collision, they are believed to be linked by a tube of chromoelectric field flux, the color string. The energy of the string grows linearly with quark separation. This energy is converted into real particles by the Schwinger mechanism. Screening of the color fields by new particles breaks the string. By quantizing excitations of the string using the conjugate coordinates of field strength and string cross-section, we recover the observed exponential spectrum of outgoing particles.

Methods based on the atomic force microscope (AFM) were implemented or developed to measure and map at the nanoscale the mechanical properties of polymer surfaces and of nanomaterials: force spectroscopy, force modulation, phase detection in intermittent-contact mode. Especially, a technique, referred as resonant contact-AFM, was developed. It is based on the electrostatic excitation of the cantilever vibration and on the measurement of its resonance frequency when the tip contacts the probed sample. A theoretical model was developed to determine the tip-sample contact stiffness from the measurement of the frequency shift. These methods were used to study several questions raised in the fields of polymer surfaces and interfaces and of nanomaterials. Surfaces of toughened polypropylene (PP) with ethylene-propylene copolymer (EP) were studied by force spectroscopy and force modulation microscopy (FMM) to characterise the effect of the blending and the moulding processes and the PP/EP viscosity ratio on the surface distribution of the EP rubber nodules. The contribution of the EP rubber to paint adhesion was also demonstrated. Surfaces of atactic polypropylene photo-grafted with acrylic acid monomers were analysed by intermittent-contact AFM (IC-AFM) with phase detection. The combination of these methods with other analytical techniques allowed characterising the chemical composition of the heterogeneous surface morphology obtained after photo-grafting. The tensile elastic modulus of polymer nanotubes and metallic nanowires was measured with force spectroscopy and resonant contact-AFM. These measurements confirmed the ability of resonant contact-AFM to quantitatively measure the mechanical properties of nanomaterials. Moreover, they showed that the measured modulus increased when the nanowires or nanotubes diameter decreases. This behaviour was explained by taking into account the effect of the surface deformation that added a surface stiffness proportional to the surface tension, or surface stress, of the material. Resonant contact-AFM was also used to characterise the variation of the mechanical properties at the interfaces in polymer blends. It was demonstrated that this technique allows the determination of the interfacial width in incompatible polymer blends. It also allowed characterising the mechanical property gradient that can appear in reactive polymer blends.

Several nanomaterials systems, both inorganic and organic in nature, have been extensively investigated by a number of characterization techniques including atomic force microscopy (AFM), electron microscopy, Fourier transform infrared spectroscopy (FTIR), and energy dispersive x-ray spectroscopy (EDX). The first system consists of boron nitride nanotubes (BNNTs) synthesized via two different methods. The first method, silica-assisted catalytic chemical vapour deposition (SA-CVD), produced boron nitride nanotubes with different morphologies depending on the synthesis temperature. The second method, growth vapour trapping chemical vapour deposition (GVT-CVD), produced multiwall boron nitride nanotubes (MWBNNTs). The bending modulus of individual MWBNNTs was determined using an AFM three-point bending technique, and was found to be diameter-dependent due to the presence of shear effects. The second type of nanomaterial investigated is the biomineralized calcareous shell of the serpulid Hydroides dianthus. This material was found to be an inorganic-organic composite material composed of two different morphologies of CaCO3, collagen, and carboxylated and sulphated polysaccharides. The organic components were demonstrated to mediate the mineralization of CaCO3 in vitro. The final system studied is the proteinaceous cement of the barnacle Amphibalanus amphitrite. The secondary structure of the protein components was investigated via FTIR, revealing the presence of β-sheet conformation, and nanoscale rod-shaped structures within the cement were identified as β-sheet containing amyloid fibrils via chemical staining. These rod-shaped structures exhibited a stiffer nature compared with other structures in the adhesive, as measured by AFM nanoindentation.

This dissertation primarily documents the quantification of the interfacial behavior of carbon based nanomaterials, which includes two categories, one is the nanofriction properties evaluation of aligned carbon nanotube carpets, few-layer graphene as well as three types of functionalized graphene nanoribbons, the second is the mechanical characterization of individual functionalized carbon nanofibers and the interfacial fracture toughness quantification in carbon nanotube/polymer derived ceramics nanocomposite. The aligned carbon nanotube carpets have a highly anisotropic friction behavior, which means the friction force are lower for transversely aligned CNTs side than for vertically aligned CNTs surface. We can also tune the friction properties of graphene ribbons by grafting different functional groups. In addition, two narrow angular regions with high friction, separated by a wide angular interval with low friction, were identified between graphene and highly oriented pyrolytic graphite. The distance between the two friction peaks is 61◦, which corresponds well with the 60◦ symmetry of individual atomic layers in the graphite lattice. The technique that involves the usage of mcirodevices and nanoidenter was used to conduct tensile tests on pristine, fluorinated and amino-functionalized carbon nanofibers, which were found to exhibit varied load-bearing abilities and unique fracture modes. The technique was also used to perform single fiber pullout experiments to study carbon nanotube/polymer derived ceramic interface.

Several nanomaterials systems, both inorganic and organic in nature, have been extensively investigated by a number of characterization techniques including atomic force microscopy (AFM), electron microscopy, Fourier transform infrared spectroscopy (FTIR), and energy dispersive x-ray spectroscopy (EDX). The first system consists of boron nitride nanotubes (BNNTs) synthesized via two different methods. The first method, silica-assisted catalytic chemical vapour deposition (SA-CVD), produced boron nitride nanotubes with different morphologies depending on the synthesis temperature. The second method, growth vapour trapping chemical vapour deposition (GVT-CVD), produced multiwall boron nitride nanotubes (MWBNNTs). The bending modulus of individual MWBNNTs was determined using an AFM three-point bending technique, and was found to be diameter-dependent due to the presence of shear effects. The second type of nanomaterial investigated is the biomineralized calcareous shell of the serpulid Hydroides dianthus. This material was found to be an inorganic-organic composite material composed of two different morphologies of CaCO3, collagen, and carboxylated and sulphated polysaccharides. The organic components were demonstrated to mediate the mineralization of CaCO3 in vitro. The final system studied is the proteinaceous cement of the barnacle Amphibalanus amphitrite. The secondary structure of the protein components was investigated via FTIR, revealing the presence of β-sheet conformation, and nanoscale rod-shaped structures within the cement were identified as β-sheet containing amyloid fibrils via chemical staining. These rod-shaped structures exhibited a stiffer nature compared with other structures in the adhesive, as measured by AFM nanoindentation.

Dissipation is an inevitable property of a mechanical system and influences the dynamical behavior and device performance. It is, therefore, crucial to study and understand the sources of dissipation in mechanical systems in order to control the dissipation present in the system. These sources of dissipation can be broadly classified in two groups: extrinsic and intrinsic mechanisms. Extrinsic mechanisms are independent of material properties and influenced by the external properties of the system, such as geometry, pressure, and temperature. Intrinsic mechanisms on the other hand, are independent of external conditions and arise from the intrinsic properties of the device material, such as defects in the bulk and the surface of the material. In this work, we closely study two extreme limits of dissipation at the opposite ends of the spectrum. First, at the high dissipation limit where extrinsic mechanisms dominate dissipation, spectral properties of the thermal noise force giving rise to Brownian fluctuations of a continuous mechanical system — namely, a doubly clamped nanomechanical beam resonator — immersed in a viscous liquid are investigated. To this end, two separate sets of experiments are performed. The power spectral density (PSD) of the Brownian fluctuations of the resonator around its fundamental mode are measured at the center of the resonator. Then, the frequency-dependent linear response of the resonator is measured, again at its center, by driving it with a harmonic force, via an electrothermal transducer, that couples well to the fundamental mode. These two separate measurements are then used to determine the PSD of the Brownian force acting on the structure in its fundamental mode. The PSD of the force noise extracted from multiple resonators with varied lengths spanning a broad frequency range displays a ``colored spectrum'' and follows the viscous dissipation of a cylinder oscillating in a viscous liquid by virtue of the fluctuation-dissipation theorem. In the second application, which is at the ultra-low dissipation limit at low temperature where intrinsic mechanisms dominate dissipation, we design and fabricate high-frequency aluminum nitride (AlN) piezo-optomechanical resonators. Furthermore, an acoustic radiation shield consisting of periodic phononic crystals is designed and implemented to further decrease dissipation. Fabrication and design of both the optomechanical cavity and phononic crystals are discussed in detail. Room temperature characterization of the ring resonator is presented and out-of-plane thickness mode of the AlN resonators has been identified. With microwave mechanical frequency and high Quality factor mechanical response, these resonators can be cooled down to quantum ground state with direct cooling methods such as dilution fridge cooling. These type of resonators can achieve efficient conversion between electrical, optical, and mechanical signals which can be utilized for quantum information science and sensing applications in the field of nanoelectromechanical systems. / 2023-09-24T00:00:00Z

The microcantilever has become a ubiquitous tool for surface science, chemical sensing, biosensing, imaging, and energy harvesting, among many others. It is a device of relatively simple geometry with a static and dynamic response that is well understood. Further, because of it's small size, it is extremely sensitive to small external perturbations. These characteristics make the microcantilever an ideal candidate for a multitude of sensing applications. In this thesis dissertation we use the microcantilever to conduct numerous physical measurements and to study fundamental phenomena in the areas of fluid dynamics, turbulence, and biology. In each area we use the cantilever as a sensitive transducer in order to probe fluctuating forces. In micro and nanometer scale flows the characteristic length scale of the flow approaches and is even exceeded by the fluid mean free path. This limit is beyond the applicability of the Navier-Stokes equations, requiring a rigorous treatment using kinetic theory. In our first study, we conduct a series of experiments in which we use a microcantilever to measure gas dissipation in a nanoscopically confined system. Here, the distance between the gas molecules is of the same order as the separation between the cantilever and the walls of its container. As the cantilever is brought towards the wall, the flow becomes confined in the gap between the cantilever and the wall, affecting the resonant frequency and dissipation of the cantilever. By carefully tuning the separation distance, the gas pressure, and the cantilever oscillation frequency, we study the flow over a broad range of dimensionless parameters. Using these measurements, we provide an in-depth characterization of confinement effects in oscillating nanoflows. In addition, we propose a scaling function which describes the flow in the entire parameter space and which unifies previous theories based on the slip boundary condition and effective viscosity. In our next study, we seek to gain a better understanding of the transition to turbulence in a channel flow. We use a cantilever embedded in the channel wall to perform two sets of experiments: first, we study transition to turbulence triggered by the natural imperfections of the channel walls and second, we study transition under artificially added inlet noise. Our results point to two very different paths to turbulence. In the first case, wall effects lead to an extremely intermittent transitional flow and in the second case, broadband fluctuations originating at the inlet lead to less intermittent flow that is more reminiscent of homogeneous turbulence. The two experiments result in random flows in which high-order moments of near-wall fluctuations differ by orders of magnitude. Surprisingly however, the lowest order statistics in both cases appear qualitatively similar and can be described by a proposed noisy Landau equation. The noise, regardless of its origin, regularizes the Landau singularity of the relaxation time and makes transitions driven by different noise sources appear similar. Our results provide evidence of the existence of a finite turbulent relaxation time in transitional flows due to the persistent nature of noise in the system. In our last study, we turn to biologically-driven fluctuations from bacterial motion. Recent studies suggest that the motion of living bacteria could serve as a good indicator of bacteria species and resistance to antibiotics. To gain a better understanding of these fluctuations, we measure the nanomechanical motion of bacteria adhered to a chemically functionalized silicon microcantilever. A non-specific binding agent is used to attach E. coli to the surface of the device. The motion of the bacteria couples efficiently to the cantilever well below its resonance frequency, causing a measurable increase in its mechanical fluctuations. We vary the bacterial concentration over two orders of magnitude and are able to observe a corresponding change in the amplitude of fluctuations. Additionally, we administer antibiotics (Streptomycin) to kill the bacteria and observe a decrease in the fluctuations. A basic physical model is used to explain the observed spectral distribution of the mechanical fluctuations. These results lay the groundwork for understanding the motion of microorganisms adhered to surfaces and for developing micromechanical sensors for rapid bacterial identification and antibiotic resistance testing.

<p>This thesis is concerned with employing the statistics of charge transfer in a conductor as a tool for quantum measurement. The physical systems studied are electronic devices made by nanoscale manufacturing techniques. In this context quantum measurement appears not as a postulate, but as physical process. In this thesis I am considering a quantum system, in particular a qubit or a nanomechanical resonator, interacting with a tunnel junction. The effect of coupling a quantum system to a tunnel junction is twofold: The state of the quantum system will be changed and there will be information about the quantum system in the statistics of charge transfer of the tunnel junction. As the first example a quantum measurement process of a qubit is considered. A common description of the system and charge dynamics is found by introducing a new quantity, the charge specific density matrix. By deriving and solving a Markovian master equation for this quantity the measurement process is analyzed. The measurement is shown to be a dynamical process, where correlations between the initial state of the qubit and the number of charges transferred in the tunnel junction arise on a typical timescale, the measurement time. As another example of a quantum system a nanomechanical oscillator is considered. It is found, that the biased tunnel junction, acting as a non-equilibrium environment to the oscillator, increases the temperature of the oscillator from its thermal equilibrium value. The current in the junction is modulated by the interaction with the oscillator, but the influence vanishes for bias voltages smaller than the oscillator frequency. For an asymmetric junction and non-vanishing oscillator momentum a current is shown to flow through the junction even at zero bias. The current noise spectrum induced by the oscillator in the tunnel junction consists of a noise floor and a peaked structure with peaks at zero frequency, the oscillator frequency and double the oscillator frequency. The peak heights are dependent on the coupling strength between oscillator and junction, the occupation number of the oscillator, the bias voltage and the junction temperature. I show how the peak height can be used as a measure of the oscillator temperature, demonstrating that the noise of a tunnel junction can be used for electronic thermometry of a nanomechanical oscillator.</p>

Owing to atomic force microscopy’s (AFM) high-resolution in both imaging and force spectroscopy, it is very successful in probing not only structures, but also nanomechanics of biological samples in solution. In this thesis, the nanomechanical properties of lipid bilayers of biological relevance and proteins of the barnacle adhesive were examined using AFM indentation, AFM-based force mapping, and single-molecule pulling experiments. Through high-resolution AFM-based force mapping, the self-organized structures exhibited in phase-segregated supported lipid bilayers consisting of dioleoylphosphatidylcholine / egg sphingomyelin / cholesterol (DEC) in the absence and presence of ceramide (DEC-Ceramide) were directly correlated with their breakthrough forces, elastic moduli, adhesion, and bilayer thickness. Results were presented as two-dimensional visual maps. The highly stable ceramide-enriched domains in DEC-Ceramide bilayers and the effect of different levels of cholesterol as well as of diblock copolymers, on the nanomechanical stability of the model systems studied were further examined. For the proteins of the barnacle adhesive, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and chemical staining with amyloid-selective dyes, in addition to AFM imaging, indentation, and pulling experiments were performed to study the structure and nanomechanics of the polymerized barnacle glue. Nanoscale structures exhibiting rod-shaped, globular, and irregularly shaped morphologies were observed in the bulk barnacle cement by AFM. SEM coupled with energy dispersive x-ray (EDX) makes evident the organic nature of the rod-shaped nanoscale structures while FTIR spectroscopy on the bulk cement gave signatures of β-sheet and random coil conformations. Indentation data yielded higher elastic moduli for the rod-shaped structures as compared to the other structures in the bulk cement. Single molecule AFM force-extension curves on the matrix of the bulk cement often exhibited a periodic sawtooth-like profile, observed in both extend and retract portions of the force curve. Rod-shaped structures stained with amyloid protein-selective dyes (Congo Red and Thioflavin-T) revealed that about 5% of the bulk cement are amyloids.