Current technologies capable of establishing bioresorbable orthopedic fixation devices and stents have broad utility for biomedical applications to improve constructive tissue remodeling. Recent studies and investigations on bioresorbable conductors, semiconductors, dielectrics, and polymer substrates offer a promising opportunity to propel the existing non-degradable bioelectronic devices to the promising bioresorbable electronics,...
Lubrication is the most means for sliding interface failure prevention because it helps separate two interacting surfaces, reduce asperity contacts and thus extend the working life of the parts. Improving the tribological performance of lubricated interfaces is a challenging work, as several influence factors are involved, such as coating, plasticity,...
Hollow biopsy needles are widely adopted medical devices for the removal of biological tissue to better identify a lesion or an abnormality observed through a physical exam or a radiology scan. These procedures can provide significantly more information than most medical tests, and they are usually performed on dermis layers,...
Global energy demand is increasingly rapidly in today’s modern world with increasing living standards all around the world. As global energy demand rises, energy efficiency has never been more crucial and that the improvement of tribological systems is critical to the progress of the global future. A large part of...
In recent years, we have seen the embryo of Industry 4.0 which has been promoting manufacturing processes towards the future with better efficiency, higher accuracy and better reliability. However, manufacturing precision has been restricted by the precision of metrology and material characterization. In other words, one can only manufacture parts...
Polymer nanocomposites have attracted great interest in recent years because of their potential as tailored materials with enhanced properties. Recent experiments have shown that polymer nanocomposites are able to achieve significant improvement in dielectrical, thermal, mechanical and other physical properties compared with their parent polymer systems. More importantly, these outstanding...
Muscle strength assessment is a standard part of any clinical evaluation. Due to the kinematic and muscular redundancy in the human musculoskeletal system, muscle strength can not be measured directly in vivo. Clinicians utilize specific postures and forces to bias the muscles of interest, then infer the muscle strength from...
Polymer nanocomposites are a class of advanced materials comprised of soft polymer matrix and nano-filler inclusions. While it has been found qualitatively that enhancements of material properties could be achieved by dispersing inorganic nano-particles into organic polymer matrix, the intrinsic governing principles of such composite has not been thoroughly studied...
High performance polymers and their composites have wide ranging application in advanced and emerging material systems. The macroscale performance of these advanced materials is often defined by interfaces that induce nanoscale changes in the microstructure or molecular conformations (termed the ‘interphase’) of the polymer. Atomic force microscopy (AFM) is an...
Predicting pediatric spinal deformity (PSD) from X-ray images collected on the patient's initial visit is a challenging task. This research provides a bio-informed framework based on a mechanistic machine learning technique with dynamic patient-specific (PS) parameters to predict PSD. We provide a geometry-based bone growth model that can be utilized...
As the technology enabling touch-sense rendering of virtual textures grows in efficacy and prevalence, so too grows the need for a standardized means of storing, transferring, and reconstituting textural signals. Furthermore, to achieve the ultra-low-latency requirements of the next generation of global communications networks, this digital texture representation must be...
Polymer nanocomposites are a designer class of materials where nanoscale particles, functional chemistry and polymer matrix combine to yield unprecedented combinations of superior physical properties. While well-defined data representation and quantitative models have been developed in material science domains such as metallic alloys, polymer nanocomposites have remained a largely untouched...
Active lateral force feedback is essential for haptic applications in which forces on the fingertip is perpendicular to or in the same direction of finger movement, such as virtual shape rendering and button click rendering. In this thesis, I first present a novel device, the UltraShiver, that can provide large...
Additive manufacturing (AM), also known as three-dimensional (3D) printing, has received considerable interests in recent years. It enables fabrication of complex, customizable parts that would otherwise be too expensive or impossible for traditional manufacturing methods. 3D printing encompasses a wide variety of processes, including photopolymerization, material extrusion, selective laser sintering,...
The functions of lubricants in moving interfaces are extensive; lubricants minimize friction, transfer heat, clean the rubbing surfaces, extract debris, and diminish wear. Rather than using separate lubricants for each of the functions, it is more desirable to make one lubricant serve multiple purposes, or a muti-functional lubricant. The goals...
The rapid development of flexible electronics enables a huge amount of bio-integrated applications with advantages of the mechanical compliance, stretchability and comformability of the devices. My dissertation further advances this area by a series of projects, which include designing and optimizing novel compliant structures, proposing novel elastomer encapsulation process for...
Additive manufacturing (AM) offers exciting advantages for the fabrication of metallic parts compared to traditional techniques, such as the ability to create complex geometries with less material waste. This is done by building arbitrary geometries in a layer-by-layer fashion, thereby giving the designer great control over the design of the...
Mixing by cutting-and-shuffling (like that for a deck of cards or a Rubik's cube) is a paradigm that has not been studied in detail even though it can be applied in a variety of situations including the mixing of granular materials. Mathematically, cutting- and-shuffling is described by piecewise isometries (PWIs),...
In recent years Additive Manufacturing (also known as 3D printing) processes have risen in use within research and industry to create complex, custom parts, which would be otherwise too expensive or even impossible to fabricate via conventional manufacturing methods. While originated as a tool for rapid prototyping, the improvements in...
Nanoelectromechanical (NEMS) systems fabricated using atomically-thin materials have low mass and high stiffness and are thus ideal candidates for force and mass sensing applications. Transition metal dichalcogenides (TMDCs) offer certain unique properties in their few-layered form – such as piezoelectricity and a direct band gap in some cases – and...
The staggered (or imbricated) lamellar ``brick-and-mortar" nanostructure of nacre endows nacre with strength and fracture toughness values exceeding by an order of magnitude those of the constituents, and inspires the advent of new robust biomimetic materials. While many deterministic studies clarified these advantageous features in the mean sense, a closed-form...
The dissertation systematically delineates the mechanically-guided deterministic assembly of three-dimensional (3D) mesostructures by compressive buckling, covering topics from mechanics concepts, design and analysis, fabrication techniques, to application opportunities. The development of approaches to form complex 3D functional mesostructures in advanced materials is a topic of broad interest, thanks to the...
Engineering design is a systematic process of identifying needs and their translation into functional systems. This is a cyclic process that alternates between the acquisition of data and the synthesis of said data to inform design decisions. Conventionally, data from physical experiments are used to explore the efficacy of alternative...
A framework is developed that models point defect diffusion and interaction with pre-existing microstructures during irradiation, including defect-defect interactions and defect sinks. This framework uses a modified diffusion potential that includes not only defect concentration, but also intrinsic stresses from the pre-existing microstructure. Various microstructures are studied in {Fe} by...
The advent of metamaterials—hierarchical structures that manifest properties beyond those found in nature through geometry rather than material composition—inspired new possibilities and research in many fields. In mechanics, periodic metamaterials exhibit behaviors ranging from unprecedented compressibility to extreme stiffness. Numerous geometric classes of metamaterials with these properties have been discovered,...
Bio-integrated electronics with advanced monitoring capabilities have garnered considerable interest as a means of expanding patient care beyond traditional hospital and clinic settings. These mechanically soft microsystems, many of which are bioresorbable and wireless, have the potential to replace bulky, rigid, and wired medical technologies by matching or exceeding their...
Biological experiments involving the manipulation and analysis of cells have always strived towards greater precision and resolution. Recent advances in micro and nanotechnology have improved the precision of manipulation and the resolution of analysis down to a single cell, thus opening new avenues of investigation. These advances have added a...
Over the last several decades, market-driven needs created a vast assortment of products with micron-sized features. To achieve the necessary levels of precision and accuracy, a synergistic approach was undertaken, where both material addition and subtraction was employed in the creation of the desired parts. However, currently employed micromanufacturing processes...
An extensive set of functional electronic properties depends on the electronic structure. These properties are directly connected to the reciprocal-space representation of electronic structure. However, there is a complementary, real-space perspective that is described by combinations of atomic orbitals. Atomic orbitals are the components of electronic structures, analogous to how...
Modeling the mechanical performance of metal produced with additive manufacturing (AM) has proven to be a challenging task. In the as-built state, these materials have been shown to exhibit strong heterogeneity and anisotropy. Even after post-processing, such as heat treatment or hot isostatic pressing and depending on the alloy, some...
Proteins and many other systems are often conceptualized as networks to access analysis methods from the field of network science. Several approaches use molecular dynamics (MD) simulations of proteins to construct networks using correlational statistics. However, in the field of network science, a well-established approach for network construction is solving...
With the increasing demand for customized products, rapid prototyping, and small-batch production, incremental sheet forming (ISF) is gaining ever-growing attention. The potential of ISF to produce parts without the use of geometry-specific dies has revolutionized the sheet forming processes. Despite its promising characteristics, ISF thus far has not been extensively...
Modern design practices rely more and more on computer simulations due to their low cost compared with physical experiments. However, it is still an elusive task to fully unleash the advantages of the simulation models while mitigating their disadvantages for designing complex engineering systems. In simulation-based design, computer simulation models...
Additive manufacturing (AM) processes have advanced rapidly over the last three decades to the point where they have the potential to fundamentally change the way complex parts will be designed and fabricated in the future. Additive methods leverage the ability to join metal particles or molten droplets in a layer-by-layer...
The heart of computational materials science lies in providing fundamental insights and understanding of materials behavior and properties across different scales. The significance of this task is highlighted by the Materials Genome Initiative and the emergence of computational tools and frameworks such as materials by design, microstructure sensitive design, and...
The successful isolation of graphene marked the advent of two-dimensional (2D) materials. Their atomically thin structures enable unprecedented electrical, optical, and mechanical properties, which have triggered significant research interests in the past decade. For instance, they are promising candidates for the fabrication of flexible electronics, biological sensors, battery electrodes, and...
ABSTRACTUnderstanding Micro-macroscopic Phenomena of Tribological Fluids and Surfaces
Mechanical power and motion are transmitted through interfaces under contact and relative motion. Friction is inevitable, which can lead to higher operating and energy costs, and severe frictional rubbing can result in material damage and cessation of motion. A deep understanding of...
Metal Additive manufacturing (AM) processes build 3D objects by heating and consolidating material in a point-by-point manner. Unlike traditional manufacturing methods, AM allows the material properties of each point in the build to vary by controlling process conditions locally. The process parameters can be considered as inputs to the AM...
In this dissertation, advances are made in understanding both the way hyporheic exchange impacts riverbed morphodynamics and the physical processes that lead to turbulent momentum transfer in the first few grains of riverbed sediments. In terms of physical advances in understanding the interplay between bedform movement and hyporheic exchange, we...
Robots can be capable partners when interacting with humans, but their value is largely dependent on how information is communicated in that partnership. In physical human-robot interaction, information is communicated via motion---configurations, velocities, forces, and torques. The autonomy interprets these implicit signals using metrics, which ultimately drive the the autonomy....
To relate the mechanical responses of hard-soft copolymer systems with their microstructures, a coarse-grained molecular dynamics (CGMD) approach is employed. With the generic bead-spring polymer model mapped from atomistic simulations, this dissertation first studies the morphology of structures with various hard-soft compositions and interactions between hard beads. Following that, this...
As opposed to the nanoscale deposition techniques often used for material syntheses, here, I focus on mesoscale material depositions and how to design interfaces to efficiently manage such deposition and potential accumulation. These deposition processes include condensation, condensation frosting, particle capture, and vaporization. Through the lens of energy and sustainability,...
Controlled delivery of foreign cargo into cells is a critical step in many biological studies and in cell engineering and analysis workflows. Recent advances in micro and nanotechnology, specifically in microfluidics and microfabrication have added significantly to the precision, accuracy, resolution and throughput of cell manipulation and analysis pipelines. These...
Integrated Computational Materials Engineering (ICME) has emerged as a transformative paradigm that enables the co-design of products, materials, and their manufacturing processes. A gamut of computational tools, such as manufacturing process simulations and multiscale materials analyses, have been developed henceforth by their respective research communities. However, it remains challenging to...
The presence of unwanted biofilms on surfaces is a great concern for industrial, naval, and healthcare fields, and many other settings. To better inhibit, remove, or harness the properties of biofilms, an explanation of how specific structural or chemical features of biofilm matrix components leads to enhanced adhesion and persistence...
Flowing granular mixtures with species differing in some property, such as size, shape or density of the grains, tend to segregate (de-mix) during flow. Since flowing granular materials are common in industry, and since segregation is often unwanted and costly, understanding and mitigating segregation is an important concern in industrial...
Flexible sheet metal forming processes possess significant potential in today’s industrial goods market with the advent of the next generation manufacturing paradigm, which put stresses on products customization and cost efficiency. However, due to the unique tooling configurations and forming mechanisms adopted in different flexible sheet metal forming processes, there...
Increasingly high global energy consumption demands effective approaches to high energy efficiency and, at the same time, paths to reduced release of carbon dioxide, a primary greenhouse gas behind global climate change. Friction reduction is a vital aspect towards making energy systems more efficient and one of the most crucial...
The viscoelastic properties of microbial biofilms have attracted great interests in recent years due to the ubiquity of biofilms and their wide range of industrial and municipal applications causing tremendous societal impacts. Biofilms are predominantly architected by extracellular polymeric substances (EPS) matrices composed of bacterial cells and biopolymers secreted by...
Although flowing granular materials have been formally studied for over two hundred years, their behavior is still poorly understood relative to fluids, solids, and gases. Sheared granular materials with differing particle properties (e.g., size, density, shape) segregate (de-mix) due to percolation (small particles fall between large ones) and buoyancy (light...