Ultra-thin drums play a crucial role in sensing applications due to their slender construction and relatively low bending rigidity. These properties render them highly sensitive to external forces. The emergence of graphene and other 2D materials has profoundly impacted the development of these devices, allowing for the creation of exceptionally thin membranes, even as thin as a single atomic layer. However, the extreme thinness of these structures introduces challenges, such as susceptibility to large deformations and nonlinear behaviour, making linear models unsuitable for mechanical analysis.

To fully harness the potential of ultra-thin resonators in practical applications, it is thus essential to comprehend their nonlinear mechanical behaviour thoroughly. Consequently, mathematical modelling and numerical simulations play a pivotal role in studying the nonlinear mechanics governing the motion and resonant behavior of these devices. This doctoral thesis investigates the nonlinear mechanics of ultra-thin membranes. Its primary objective is to develop analytical and numerical methodologies that will facilitate the future design and analysis of these structures for various applications...

This thesis investigates the forces and torques acting on acoustically levitated cuboids, with the aim of improving translational and rotational control in acoustic transportation applications. Traditional trans port methods rely on mechanical pick-and-place systems, which introduce challenges such as fragility and contamination. Acoustic levitation presents a contactless alternative that eliminates these issues. To address the research question: “1: Can we develop a model to determine the stiffness and torsional stiffness values of acoustically levitating cuboids of arbitrary shape, in an arbitrary pressure field?” the study begins by reviewing the fundamental principles of acoustic levitation, including acoustic radiation force, the Gorkov potential, and phased array transducer (PAT) configurations. It then explores various modeling approaches for determining the forces and torques on levitated objects, comparing the strengths and limitations of Gor’kov-based, finite difference time domain (FDTD), finite and boundary element method (FEM/BEM), and a proposed simplified trapping model.
The findings show that while the simplified trapping model lacks predictive accuracy, a Finite Element Method (FEM) model was introduced as a more reliable alternative. The FEM model, using a sound hard boundary assumption, agrees well with prior models of forces on non-spherical particles, that cannot be predicted with Gorkov’s or King’s method, and its implementation in Comsol makes it more accessible to a broad audience. In addition, the model predicts accurately the torques that act on non spherical particles and for the first time such a model is experimentally verified for all three translational and three rotational degrees of freedom....

Most micro- and nanomechanical devices are designed to operate within the linear dynamic range by using simple geometries, primarily due to the limited knowledge in utilizing nonlinearity and constraints in fabrication techniques. However, it is anticipated that the scope of applications and fundamental research can be significantly expanded, if these tiny systems can be precisely engineered to account for and exploit their various nonlinear dynamic behaviors. This thesis provides a comprehensive study on the optimization of dynamical properties of high-Q nanomechanical resonators, spanning from linear to nonlinear dynamics and evolving from single-mode to multi-mode analysis.

We first give an introduction to the development of micro- and nanomechanical resonators in Chapter 1. We focus on their unique mechanics, including very low dissipation and strong nonlinearities. Furthermore, we elaborate on the motivation behind this thesis and the need for linking engineering optimization with micro- and nanomechanical resonators. Followed by Chapter 2, we elaborate on the methodology we use throughout this thesis, including fabrication techniques of nanomechanical Si3N4 devices, characterization approaches by optical measurements, and modeling procedures for structural dynamics. Among all methodologies, we highlight the Finite Element (FE)- based Reduced Order Models (ROMs) that can accurately capture the geometric details and boundary conditions, which facilitate the design of resonators with predictable dynamical properties.

We start from investigating linear dynamics of Si3N4 nanostrings in Chapter 3, where the tuning effects of their soft-clamping supports on resonance frequency and Q-factor are evaluated. We experimentally and theoretically reveal a trade-off between maintaining high stress and low stiffness of the supports in designing high-Q resonators fabricated with initial strain. By optimizing this trade-off with our soft-clamping design, we obtain a 50% enhancement of Q-factor compared to doubly-clamped string resonators. With stronger drive levels, in Chapter 4, we show that the nonlinear dynamics can also be substantially tailored by soft-clamping supports. Through careful engineering of support geometries, we introduce softening nonlinearity by stress-induced buckling, allowing precise control over the nonlinear dynamic responses in doubly supported nanostrings, which conventionally exhibit hardening behaviors.

Based on the accurate modeling of both linear and nonlinear dynamics that is validated by experiments, we integrate our FE-based ROM technique with a derivative-free optimization algorithm for the design of nonlinear mechanical resonators in Chapter 5. By optimizing the support’s geometry of our nanostrings, we show that the proposed methodology is not only capable of handling a single optimization goal, but also multiple conflicting objectives, such as the simultaneous enhancement of Q-factor and the Duffing constant. Besides, we generate Pareto frontiers that visualize the trade-offs among multiple optimization objectives, verify the optimized results with brute-force simulations and validate the numerical framework with experiments.

Apart from the dynamics in a single mode, we observe modal interactions between multiple vibrational modes of our nanostrings in the strong nonlinear regime. In Chapter 6, we demonstrate that soft-clamping techniques, commonly utilized to achieve high-Q resonators, can be employed to engineer mode coupling. We verify the analytically derived two-degree-of-freedom system between the lowest two out-of-plane modes by FE-based ROMs and experiments. We further reveal the significant impact of multi-mode interactions on the nanostrings’ frequency response, demonstrating additional opportunities to tailor the nonlinear dynamics of mechanical resonators facilitated by soft clamping. Moreover, we highlight the design potential of soft-clamping supports through the geometric optimization of two-mode coupling, showcasing the effective Duffing constant of the driven mode can be increased by 70%, as well as the onset of mode coupling can be geometrically programmed to either facilitate or inhibit its occurrence.

We conclude all works presented for achieving the optimization of nonlinear dynamics in nanomechanical resonators, and give an outlook for future directions in Chapter 7.

3D imaging of subsurface structures at the nanoscale is a longstanding challenge in microscopy. Ultrasound enables subsurface imaging, but nanometer depth resolution requires high-frequency sound waves, achieved by heating with pulsed lasers. Combined with Atomic Force Microscopy (AFM), which offers atomic-scale surface resolution a promising candidate for full 3D nanoscale imaging emerges.

This thesis focuses on the development of such a combined ultrasound-AFM system.
Novel optical detection techniques are introduced for both the ultrasound and the AFM, enabling simultaneous operation.

Acoustic waves up to 100 GHz are generated and detected, used to characterize the thickness and adhesion of thin films. We demonstrate that the conical AFM tip acts as an acoustic lens, focusing the wave into the tip apex. When in contact with a sample, changes in the reflection signal confirm acoustic transmission—opening the door to true 3D nanoscale imaging.

Multiple recent events have shown the alarming vulnerability of infrastructure on sea to sabotage. This infrastructure can be monitored and protected with passive sonar systems, which provide a number of advantages over other surveillance methods such as RADAR or active sonar. An overview of different localisation methods suitable for the Dutch littoral zone that perform bearing estimation, ranging or complete localisation on the surface plane is made from methods available in literature. From this overview a proposal is made to select cepstral ranging for further research, as there is a limited amount of literature available on this subject. Experimental data from the Dutch coastal area has been gathered with a RHIB and stationary sensor to verify important parameters for both computation and the ranging environment. An effective cepstral ranging method based on experimental data has been developed, although ranging with tidal effects and SNR mismatch remains somewhat problematic. To compensate for this a novel ray tracing method based on open-source measurements has been developed that offers a significant increase in accuracy while effectively compensating for variations in bathymetry and tide.

The nonlinear dynamics of nanomechanical resonators has drawn great interest for applications in sensing, material characterisation, and for uncovering fundamental interactions at the nanoscale. In this thesis, we explore multi-tone excitation as a route towards extracting the full nonlinear reduced order model of a multi-mode nanomechanical resonator. By driving at two frequencies, the nonlinear terms in the equation of motion will cause the generation of motion at sum-frequencies. For certain combinations of the fundamental tones and at sufficient drive levels, this motion can be detected. By analysing the amplitude of the response, the relevant nonlinear reduced order model parameters can be extracted.
In this thesis we present a theoretical analysis of a general nonlinear reduced order model excited by two-tone excitation, a description of the methodology to estimate nonlinear terms, and an experimental setup to perform these experiments. The methodology is applied on a string resonator with non-ideal supports, to estimate most nonlinear terms in its modal equations of motion for the first two modes. These results are in relatively good agreement with results estimated using backbone curve estimation and numerical simulations for a string.
The reduced order model, resulting from these measurements done with the presented methodology, could be used for validating nonlinear models, by characterizing nonlinearities in resonant systems, and for designing nonlinear mechanical systems with accurately tuned nonlinear properties.

Diamagnetism can be used for energy-less levitation, while allowing for friction-free movement of objects in vacuum conditions. A very suitable material can be found in Highly Oriented Pyrolytic Graphite(HOPG), which not only has relatively high diamagnetic properties, but also electrical properties which allow for contactless actuation through electrostatic forces. These properties open up the possibility for the design of a multiple degree-of-freedom(DOF) levitating precision motion stage. To this end a design was created consisting of a permanent magnet array, which is covered by a thin PCB, housing multiple electrodes. Above this PCB a square HOPG plate was made to levitate, which can be actuated in the vertical and lateral directions, as well as be rotated out-of-plane. Analytical models and FEM simulations were produced to find the dimensions of this design so that optimal performance could be achieved. An experimental setup was designed and manufactured to measure the performance of the design. It was shown that for voltages below Dutch main's voltage (230V), movements within the micrometer and millirad range could be achieved. Because of environmental disturbances, it was not possible to show movement at the nanometer scale, since these disturbances were in the submicron range. It can however be analytically calculated that for actuations of 1V, displacements of less than 1nm can be achieved. Another design challenge provided itself in the separation of the DOF's, since the electrostatic force always acts in the vertical direction, due to the attraction between the electrodes and the levitating plate. That's why the electrode set-up on the PCB was engineered in a way that rotations produced by lateral displacements could be cancelled by counter-actuation. This method was experimentally proven to work. It was then also shown that with this multiple electrode set-up, movement could be produced along a diagonal line, which shows that the plate could be made to move in multiple dimensions at once, as to be expected of a multiple DOF precision motion stage. This precision motion stage was manufactured at a fraction of the costs of comparable commercial multiple DOF precision motion stages that are currently available.

Silicon Photonics is a dynamic field of research for developing new sensing technologies. In the domain of biomedical imaging, much effort is put to design photonic sensors as an alternative to commonly used piezo transducers for detecting ultrasounds. Piezo transducers are popular due to their cost effectiveness but they have some disadvantages such as limited bandwidths, difficulty of miniaturisation for achieving higher image resolutions and high sensitivity to electromagnetic noise. On the other hand, photonic sensors can achieve much higher bandwidths, be easily miniaturised and are more energy efficient. The most common photonic sensing device is the micro ring resonator (MRR). When a laser light propagates inside them, for certain laser wavelengths, resonance occurs and causes a sharp change of light intensity. Whenever an ultrasound wave hits the ring resonator, deformation occurs and causes a shift of the resonant frequency. This amount of shift is tracked to characterise the ultrasound wave. Currently, MRRs are not sufficiently sensitive for detecting weak ultrasounds. Therefore, this project was aimed at improving ring resonator sensitivity to ultrasounds by applying a patterned polymer layer on top of a MRR.

To study the effect of a patterned polymer on ultrasound sensitivity: First a FEM simulation was conducted to compute MRRs sensitivity to ultrasounds with different polymer configurations. Then multiple fabrication methods were tested to produce a polymer pattern on top of a MRR. Finally, an ultrasound characterisation was done with the fabricated patterns to determine and compare sensitivity results with the simulation and conclude about the patterning effect.

One way to tackle the rise in antibiotic resistance, is to develop new techniques for testing the susceptibility of cells to antibiotics. In this paper, a comparison is made between a novel bacterial susceptibility testing method and a modification on this method. Both methods rely on bacterial samples deposited on graphene cavities, where the bacteria will stick to the graphene by the addition of APTES. By making use of a 632.8 nm He-Ne laser, the sample is probed, and the cavities then serve as ultrasenstive sensors for determining bacterial nanomotion. The existing method (single spot readout) is based on focusing a laser on graphene drums, where the drums are read out one at a time by the use of a photodiode. The modified method (parallel readout) makes, by the addition of one lens, use of an expanded laser, and a CMOS camera. At 100 frames per second, four drums are read out simultaneously. This technique hypothetically makes very high throughput possible for antimicrobial testing.

Both methods rely on converting a signal based on the intensity of the incoming light to the membrane deflection in nanometer, and the bacterial motility is found by taking the variance. The comparison of the two methods is done by performing multiple experiments, in order to relate the quality of the signal by finding the standard deviation (noted as S) of the variance of the deflection σ_z² . 

From an analysis of S, statistical quantities describing the distances between probability distributions have been conceived, and a criterion is proposed to differentiate between the noise levels of the two techniques. One such quantity is the normalized distance between the signals of two types of experiments, the one being an experiment without bacteria as a reference and the other being an experiment with living bacteria.
In the case of hypermotile bacteria, parallel readout has an average variance of deflection of 5.95 nm², it is substantially higher than the method of single spot readout, having average 2.92 nm². The unitless metric D for the distance between two signals however shows that both methods score similarly in probing nonmotile (∆-MotAB) E. Coli, as for the parallel readout the measure has for ∆-MotAB a value 0.34 and for single spot readout it has the value 0.31. In the case of hypermotile (7740) E. Coli, parallel readout scores again better with a value of 2.35 versus 0.39, which is the value obtained for single spot readout.

Finally an outlook is given where interesting findings have been summarized. With the use of power spectral densities and heatmaps of either average intensity or variance of the signal, interesting phenomena are noted and are topics for future research.

Nanomechanical resonators made of two-dimensional (2D) materials are the subject of intensive research due to their remarkable properties, allowing them to operate at high frequencies with high sensitivity. However, dissipation losses and manufacturing issues have prevented them from reaching their full potential. This thesis aims to overcome these challenges by dry-transferring 2D materials onto a MEMS and clamping them using electron beam-induced deposition. By in-plane straining the membranes using MEMS, the tensile energy is increased, thereby diluting intrinsic losses. This approach increased the Q-factor of 2D material resonators by 91% and allowed measuring forces down to sub-piconewtons, outperforming commercially available silicon-based force sensors.

This thesis discusses several studies on magnetic two-dimensional (2D) materials, focusing on their nanomechanical properties and the behavior of resonance frequencies in response to temperature changes. These studies employ nanomechanical resonators, specifically suspended membranes (drum resonators) of 2D magnetic materials. The frequency response of these resonators is measured using optical excitation combined with an interferometric setup, allowing identification of resonance frequencies. By altering the temperature of the resonators, the resonance frequency shifts as the strain within the 2D material changes. This strain change is partially magnetostrictive in origin due to changes in the magnetic order within the materials, offering a method to study these magnetic characteristics...

Hermeticity is a measure of how well a package is leak-tight. Many Micro-Electro-Mechanical Systems (MEMS) sensors, actuators, and microelectronic devices need a defined cavity environment for optimal performance, hence measuring the package leak rate is critical for lifetime prediction. MEMS devices are generally packaged through the wafer-bonding technique. The MEMS device is produced on a wafer with a cavity and bonded to a cap wafer to seal the hole. Reducing the cap wafer thickness allows it to deflect due to the cavity interior-exterior pressure differential. Consequently, if leakage occurs, the deflection will
change. By measuring these deflections, it is possible to quantify leak rates.

In order to use it as an in-line testing process, this research aims to determine the accuracy of the deflection method for determining the leak rates. To achieve this, our approach involved designing and leak testing test structures (or devices) using an experimental setup that can vary pressure, supply desired species
inside a vacuum chamber, and measure deflection using an interferometer to determine leak rates. Deflections are converted to leak rates using a formulated analytical expression, subsequently utilized to determine the error involved in measuring leak rates.

Using the experimental setup, the test devices were effectively characterized for sensitivity using pressure-induced deflection measurements, with experimental sensitivity values closely matching the theory. Further, air leak testing was performed on devices interconnected with nanometer-gap size leak channels to
gain first-hand knowledge of leakage. Experimental leak rates matched well with analytical models, proving that flow through devices having leak channels can be characterized. Ultimately, the setup enabled successful helium leak testing of devices without any defined leak channels.

The helium leak-tested samples were circular membranes of diameters: 2000, 1600, 1400, 1300, and 1100 μm with a thickness of 40 μm bonded to a cavity depth of 3.24 μm. Uncertainty analysis associated with leak rate measurement revealed that when considering a certain cavity depth and membrane thickness,
the membrane with the largest diameter would exhibit the least amount of uncertainty. This was also observed through experiments, for the diameter of 2000 μm, a clear linear trend of deflection reduction due to the helium leakage was observed during a two-week period of deflection measurements. Whereas, for the diameter of 1100 μm, it was not possible to observe the same linear trend of deflection reduction, indicating that even more no.of.days is required to determine an accurate leak rate.

In the end, a short analysis was made using the cavity design having the 2000 μm membrane, which had the least uncertainty in measuring the leak rate. This analysis aimed to ascertain the designed test structure’s usefulness in measuring leak rates of the MEMS packages. Based on the analysis, it was concluded that large-volume wafer-bonded MEMS packages (> 1 mm3) with an acceptable cavity pressure increase of 10 mbar could be tested using the deflection method and our proposed test structure design to guarantee their lifetime.

Non-Destructive Testing (NDT) of infrastructures has become an increasingly prominent topic in contemporary society with great significance in terms of safety, economy and environmental protection. Acoustic Emission (AE) technology is a representative NDT technology based on passive ultrasonic guided waves, which has the advantages of large coverage, low energy consumption and rapidity but also puts forward higher requirements on performance specifications of sensors, such as sensitivity, bandwidth, signal-to-noise ratio and miniaturization. Silicon photonics employs silicon as an optical medium to create sub-micron precision photonic systems, which provides promising scope for next-generation sensors with ultra-high sensitivity, small footprint and special functionalities. Oriented towards the requirements from AE applications, this project proposes the first silicon photonic micromechanical AE sensor based on micro-machined membranes, with an ambition of replacing the conventional piezoelectric sensors. The prototype design presented in this work includes two options with different cladding materials, which is capable of a peak velocity sensitivity of more than 75dB[V /(m/s)] and a wide operating frequency range of 100 ∼ 1000 kHz. The overall performance of the proposed design is comparable to that of mainstream piezoelectric AE sensors, while the footprint is reduced to about 1/40. In the design process, a complete design methodology for opto-mechanical AE sensors is developed, which allows rapid design with good agreement with simulation results.

In a world increasingly dominated by technological advancements, the demand for high-quality microphones has never been more present. Seamless speech recognition and the development of userfriendly hearing aids remain significant challenges. State-of-the-art micro-electromechanical system (MEMS) microphones are reaching their bottlenecks in terms of thermo-acoustic noise, caused by the acoustic resistance of the parallel plate capacitor. This constrains the achievable signal-to-noise ratio (SNR). This thesis presents a novel solution to address these challenges through the application of silicon photonics technology in the development of a silicon photonic microphone. Silicon photonics is a technology that uses silicon as an optical medium to create photonic systems with sub-micrometre precision, which can be used to create ultra-sensitive sensing devices. The optical sensors are fabricated on standard silicon-on-insulator (SOI) wafers, allowing for seamless integration with the precise and cost-effective complementary metal-oxide-semiconductor (CMOS) process. The optomechanical
sensitivity of the proposed microphone is derived for three different cladding materials that could be deposited on the wafer in the fabrication process. The thermal acoustic noise of the microphone is quantified. As the integrated photonic circuit does not require a backplate the design potentially reduces the thermal acoustic noise of current microphones by 44 %. The optimized design for the laboratory setup that is considered for this thesis can theoretically result in an SNR of 73.1 dB, which is roughly 5 dB more than the current state-of-the-art microphone technology.

Creating a lateral force on a finger touching a touch- screen can provide the sensation of a bump in the surface, and generate a pulling sensation, which could enhance the experience of operating a touchscreen. The Ultraloop, a device built to generate such a lateral force on a finger in contact, works by producing flexural traveling waves that push the finger. However, its shape is not simple to manufacture. Moreover, its shape is inconvenient to place in most touch input interfaces, which often appear in flat devices. A flat UltraLoop is proposed providing similar traveling wave force feedback, fitting the form factor of flat human-machine touch interfaces better. Furthermore, the new shape allows for manufacturing from a sheet of aluminum, using a cnc. The flat Ultraloop works by actuating two orthogonal modes at around 38k Hz, with a phase shift of 90 degrees, similarly to the Ultraloop. To validate the performance, force measurements have been conducted showing a maximum lateral force of 0.3N. Also, the influence of the normal force, phase, and finger motion on the lateral force is investigated. Lastly, we present a demo showing application of the flat Ultraloop, simulating a spring and a bump.

Acoustic levitation is an novel method that could lend itself very useful to fast and precise transportation of small objects. To verify the acoustic field and the modelling assumptions, the acoustic field must be visualised and quantified. Different methods to visualise a pressure gradient are investigated and rated against design requirements. These requirements are: 1. difficulty, as the setup should be buildable within the period of a MSc. thesis. 2. Time per measurement and 3. measurement sensitivity. It is decided that using a double coincidence spherical mirror schlieren setup is most suitable measurement method. To capture the high speed sphenomena of ultrasound acoustic waves in air, the schlieren light source is pulsed and matched to the frequency of the acoustics to ’freeze’ the acoustic wave in the air. Parameters that influence the schlieren image are identified and studied. These parameters are duty cycle, cut-off, ISO, light source phase delay and light source frequency. A horizontal cut-off is determined as the best, while it is determined that the other parameters can be adjusted dependent on the acoustic field. The acoustic field generated by double phased array is observed. Trap locations and types can be identified using the schlieren system. Quantification of the schlieren images has been attempted but without satisfactory results, mainly due to an interesting observation regarding a correlation between the camera focus distance and the pressure gradient. The schlieren system is a useful research tool and successful at visualising
the pressure gradient under the assumption that it is constant over the optical axis. Further research is needed to for quantification and to assess the impact of the observation.

This thesis explores the challenges of using ultrathin graphene membranes in microelectronic mechanical sensors (MEMS) technology, specifically in the development of MEMS microphones. Graphene, being only an atom thin and one of the strongest known materials, offers promising potential for further miniaturization of MEMS microphones. However, the mass loading effect on the graphene membrane can impact the device’s resonance frequency and bandwidth.To address this issue, this study analyzes the dynamic response of the graphene membrane under different pressures and membrane parameters, such as diameter and thickness. The membranes are fabricated by using chemical vapour deposition, after which the membranes are transferred over a cavity. The measuring setup uses a laser Doppler vibrometer to measure the deflection of the membranes and investigate their dynamic response. Pressure-dependent experiments are performed to measure the resonance frequency of the membrane’s response, and the relationship between the radius, thickness, and resonance frequency is explored. By doing these measurements we explore the effect of air loading to investigate the ultimate performance limits of graphene membranes for microphone application.
The experimental results show a clear presence of the air loading effect and align with earlier models of the resonance frequency with mass loading effects. The thesis validates the accuracy and reliability of the measurements and contributes to the body of knowledge surrounding the topic. The limitations of the study include fabrication imperfections and setup difficulties like a limited bandwidth of the piezo-shaker used for the actuation of the membranes. The assumptions made about limited cavity effects are also discussed. Future research could explore the impact of an added backplate with venting holes for capacitive readout. Next to that, the influence of air loading on the system’s damping could be researched.

Two-dimensional (membrane) materials have been receiving much scientific attention due to their unique material properties that can be used to study the smallest physical phenomena. One such material is graphene, perceived as the holy grail in material physics, due to its unique material properties. Its aspect ratio diminishes the bending rigidity and allows wrinkles, ripples and other morphological imperfections to dominate the mechanical behaviour. Applying tension is a necessity to control these geometrical imperfections and simultaneously opens up pathways to study physical phenomena such as magnetism, superconductivity, optics and much more. Typically, this tension is applied using electrostatic forces, which alters amongst others, the electric properties of the material. Mechanically applied tension offers a solution to this problem but comes at the cost of difficult manufacturability. In this work, a new method to incorporate 2D materials with N/MEMS is presented. The dynamics of mechanically tensioned graphene are probed in linear and nonlinear regimes. The former regime finds the exact opposite of what is observed in electrostatically tensioned membranes. The latter shows exotic nonlinear effects that can be tuned by applying tension. Furthermore, it is identified that the dynamics of the MEMS device are coupled to that of the resonating membrane despite their mass and stiffness being roughly five orders of magnitude apart. The bottleneck of this project is the adhesion force between the two is insufficiently strong to apply significant strain allowing slippage to occur.

Micro and nanomechanical resonators are essential to the state-of-the-art communication, data processing, timekeeping, and sensing systems. The discovery of graphene and other two-dimensional (2D) materials has been a profound source of inspiration for the next generation of these devices, owing to their exceptional mechanical, electrical, and thermal properties. However, alongside their advantages, the atomically thin nature of these resonators also presents its own unique challenges, as the dynamic response of these resonators rapidly becomes nonlinear, where nonlinear coupling and dissipation processes manifest. To unleash the full potential of these resonators, a comprehensive understanding of the emerging nonlinear phenomena is crucial. In this pursuit, this thesis studies nonlinear dissipation pathways in 2D material resonators that arise from the coupling of their internal mechanical modes to each other as well as to theirmicroscopic physics. The thesis consists of six chapters.