As we all know, teeth are typical brittle fracture material; there will be no apparent signs or painful experiences for patients to be aware of before the crack becomes challenging to control and restore. In addition, conventional dental diagnostics aids are partially effective in diagnosing structural defects such as cracks in teeth. Therefore, a new detection method, Quantitative Percussion Diagnostics, usually used to test the structure’s instability, seems like a good choice for doctors to detect the crack before it goes to an irreversible status. But the natural cracked tooth samples are hard to test and analyze to get the actual cracks status of the tooth since the extraction processes produce additional cracks. In addition, most crack growth of the natural teeth is vertical downward, so if we directly fatigue the intact replica tooth, there’s no way to get regular, consistent crack. Therefore, a method of printing a notched 3D replica tooth using a glass-filled resin polymer with mechanical properties similar to dentin was established. After fatiguing on a specific machine, the replica teeth containing such a simulated fatigue crack were tested using Quantitative Percussion Diagnostics (QPD). The results were consistent with QPD data for cracked natural teeth. Besides, the NanoCT scanning results reveal that our methodology can form a short but sharp vertical crack extending from the notch tip. It can be helpful for future research to connect the QPD test results and the internal crack status in a natural tooth.

Conventional nondestructive testing (NDT) techniques used to detect defects in composites are not able to determine intact bond integrity within a composite structure and are costly to use on large and complex shaped surfaces. To overcome current NDT limitations, a new technology was utilized based on quantitative percussion diagnostics (QPD) to better quantify bond quality in fiber reinforced composite materials. Experimental results indicate that this technology is capable of detecting 'kiss' bonds (very low adhesive shear strength), caused by the application of release agents on the bonding surfaces, between flat composite laminates bonded together with epoxy adhesive. Specifically, the local value of the loss coefficient determined from quantitative percussion testing was found to be significantly greater for a release coated panel compared to that for a well bonded sample. Also, the local value of the probe force or force returned to the probe after impact was observed to be lower for the release coated panels. The increase in loss coefficient and decrease in probe force are thought to be due to greater internal friction during the percussion event for poorly bonded specimens.

NDT standards were also fabricated by varying the cure parameters of an epoxy film adhesive. Results from QPD for the variable cure NDT standards and lap shear strength measurements taken of mechanical test specimens were compared and analyzed. Finally, experimental results have been compared to a finite element analysis to understand the visco-elastic behavior of the laminates during percussion testing. This comparison shows how a lower quality bond leads to a reduction in the percussion force by biasing strain in the percussion tested side of the panel.

Even about 70% of our planet is covered by water, lack of access to clean water is still a pervasive problem disturbing people all over the world. Water problems are deemed to be worse in future, given the rapidly growing population. To solve these problems calls out for a tremendous amount of research to be conducted to develop new methods/technologies of economically purifying water and harvesting water, as well as reducing associated negative impact on the environment.

In this study, we investigated water condensation at a cooled surface and the impacts of the surface property and temperature. A device was designed and developed to collect the water condensation rate in a controlled environment. The Alumina surface was used as a substrate to collect water condensation under various cooling levels of the surface. Experiment data show that the water condensation rate rapidly decreases as the difference between the surface and environmental temperature goes down. Graphene is 2D carbon materials and It is a sheet of single-atom-layer thickness which consist of sp2-hydridized carbon atoms arranged in a hexagonal honeycomb structure. It offers many super properties including high electrical and thermal conductivities, great mechanical properties. To investigate its presence’s impacts on water condensation rate, the Al surface randomly dispersed with graphenes was tested under the same condition to study the impact of the graphene presence on the water condensation rate. No obvious influence was identified. The study is important to investigate the surface’s enhancement of phase change and water harvest from ambient air.

Microgap defects (MGDs), including cracks and fractures in teeth, can lead to irreversible damage, potentially leading to tooth extraction. Early detection of MGDs is pivotal in avoiding permanent defects through appropriate treatments. Quantitative percussion diagnostics (QPD) is a non-destructive method that has been shown to detect MGDs in teeth. The goal of is the present research was to use finite element analysis (FEA) models to better understand the behavior of various MGDs in different tooth geometries and the patterns of QPD force responses generated for teeth with MGDs. This present research analyzed the shape of force versus time plots of QPD results and how they are affected by different MGD types and conditions in both single rooted premolars and double rooted molars. FEA models were constructed based on scanned, converted, and meshed 3D tooth geometries, and by implementing various MGD types, such as vertical cracks, oblique cracks, apical root cracks, damaged PDL and PDL lesions. FEA models were also exercised with different MGD conditions, including crack lengths and gap spaces. A percussion rod contains a force sensor, which was also included in all FEA models to simulate the clinical QPD measurements, capturing percussion force as a function of time. The simulated QPD measurements are analyzed, validated, and discussed in the present work. The results of FEA models are consistent with observed in vivo clinical results and confirm the capability of QPD for detecting MGDs in teeth. These FEA results not only provide insights into the distinctive characteristics of results corresponding to various MGD types and conditions but also explain the reasons contributing to shape changes in percussion force versus time results. Furthermore, a novel approach involving 3D printed replica teeth was also developed to address the limitation of obtaining in vivo conformational data. This innovative method enhances the foundation of the study by using replica teeth to support the understanding gained from FEA simulations.

We describe a theoretical framework for predicting bulk nanobubble size of any given combination of a gas and water, based upon the force balance at the gas/liquid interface. We show how this balance can develop between the internal pressure, external pressure and surface tension, and the electrostatic repulsion of hydroxide ions adhered to the surface of the nanobubble that gives rise to their relatively high negative zeta potential. We also analyse the adsorption of hydroxide ions at the surface of the nanobubble and the dependence of nanobubble formation on pH and the required initial size of a bubble that leads to the formation of a stable nanobubble. Further analysis is carried out on the velocity of the bulk nanobubble due to Brownian motion, and its effects on the rates of diffusion of the gas into the water, as well analysis on the interaction between hydroxide ions and oxygen molecules to infer the inhibition of their diffusion. Future applications and methodologies for applications, based on the equations proposed are also discussed.

Nanobubbles (NBs) have been studied for more than 20 years. One of the two types of NB, the bulk NB, with its extraordinary physical, chemical and biological properties, drew a lot of attention among researchers. However, the fundamental mechanisms of NB generation, stability, longevity and ability to bind nanoparticles are far behind the development of its applications in the industry.We started from studying the generation of NBs with an alternating magnetic field, and studied NB clustering effects with different kinds of nanoparticles that include CaCO3 and nanoscale Polystyrene beads. Furthermore, we tested NB’s effects on the \textit{ex vivo} dissolution of human atherosclerosis plaque. More recently, the NB-nanoparticle clustering mechanism was studied based on established DLVO theories and experimental data. The technologies employed for characterizing NBs, nanoparticles and clusters include Nanoparticle Tracking Analysis (NTA), Dynamic Light Scattering (DLS) with zeta potential measurement and Transmission Electron Microscopy (TEM). Intravascular Optical Coherence Tomography (IVOCT) and Micro Computed Tomography (Micro-CT) were used to characterize the volume of plaque in coronary/periphery arteries and aortic valve tissue, respectively. \par It turns out that Bulk NBs are able to attract not only cations or nanoparticles with dipoles, but also hydrophobic nanoparticles that are nearly electroneutral considering hydrophobic attraction. It provided more insight in the interaction between nano-objects at the nanoscale. The research on the \textit{ex vivo} dissolution of human plaque based on NB clustering also promotes the idea of developing NB treatment methods for atherosclerosis, the most lethal chronic disease.

It is key to consider a material's mechanical properties when determining its use for any given application, including biomaterial implantations. One such characteristic includes the fatigue life, which is determined by repeatedly cycling specified amounts of load on any given material [2]. The fatigue life is then measured according to how many cycles of load the material can undergo before fracture [2]. When a material is introduced to the human body it is usually expected that the life of the material will not match that of the patient. It is crucial to understand the fatigue life of the material before implantation to pre-diagnose how often and when the implant will need to be replaced.

The purpose of this project is to help determine and compare the fatigue behaviors of a commonly used biocompatible coating on Titanium 6-4 metal alloy. The comparison will help identify how the material properties vary with the addition of calcium phosphate when compared to the bare alloy itself.

Multiple, small rectangular samples were cut by electrical discharge machining (EDM) of which half were covered with calcium phosphate coating. Fatigue crack initiations and propagation would then be analyzed using scanning electron microscopy (SEM) to help determine the nature of the damage processes. It was found that the fatigue life of the coated samples varied at different stresses but was greater than the bare samples, and particularly high in the 900 MPa - 1000 MPa stress range.

Frontalis suspension is a commonly used surgery that is indicated in patients with droopy eyelids (blepharoptosis) and poor levator muscle function. The surgery is based on connecting the tarsal plate of the droopy eyelid to the frontalis muscle with various slings made either from fascia lata tissue or synthetic materials. However, one of the main complications of this surgery is the high rate of blepharoptosis recurrence, which has been reported for some slings as high as 100%.

We initiated a collaborative multidisciplinary research to explore the effect of choice of sling material on this common problem. Two different experimental setups for testing the behavior of various sling materials in-vitro have been developed. Using our first experimental setup, we explored possible gradual permanent elongation of sling materials due to cyclic loading caused by eye blinking. In addition, a more sophisticated second experimental setup was developed to investigate fatigue behavior of different implants under physiologically relevant conditions.

We could show that physical changes such as permanent elongation, and holding load drop in the slings could happen under fatigue conditions caused by eye blinking. These changes can contribute to the failure of the frontalis suspension slings and recurrence of blepharoptosis. Our experiments show that different sling materials exhibit significantly different responses. The results of the present study indicate that characterizing the in vitro fatigue behavior of different sling materials can lead to a better understanding of what causes high recurrence rates in frontalis suspension. The characterization methods developed can also be used to improve material selection as well as assist in the development of new materials for this procedure.

Many structural applications require a material that is both lightweight and corrosion resistant, for which aluminum and its alloys may be considered for use if not for their relatively low strength. By improving strength of aluminum through the Hall-Petch mechanism, it could become a more suitable choice for many structural applications. Cryomilling is used as a production technique to strengthen aluminum by reduction of grain size to the 20-50 nm range. Although the powders produced by cryomilling are well within the nanocrystalline regime, the powders experience significant grain growth during consolidation to a solid body. Cryomilled powders have been shown to remain nanocrystalline by introducing a nano-diamond, diamantane to the grain boundaries. To better characterize the thermal stability of the cryomilled powder with diamantane, Differential Scanning Calorimetry (DSC) was used to measure the isothermal heat flow in the 0.6Tm to 0.9Tm range. A model was developed to correlate the isothermal DSC signal to a grain growth curve and grain growth parameters were elucidated by assuming variable boundary mobility with a sigmoidal form. The model revealed a tendency for boundary mobility to transition from an athermal grain growth mechanism to standard thermally activated grain growth. Grain growth parameters were compared to shed light on possible mechanisms of aluminum-diamantane involvement during grain growth. Powders and consolidated samples with very low concentrations of diamantane and with magnesium were observed by TEM, SEM and XRD, and compared both separately and together to characterize the how thermal stability is affected by diamantane concentration and the presence of magnesium.

Understanding fatigue is important to the success of dental materials as evident from the eventual failure of restorations and cyclic loads during mastication. However, detection of such failures often poses clinical challenges as most cracks are invisible or subsurface when initiated and only identified when catastrophic failures occur. Current detection methods are limited in clinical application. Therefore, the aim of this research study was to design a test method and parameters that simulate the oral environment to assess the detection of crack initiation and growth using quantitative percussion diagnostics (QPD) technology. Nine 3D tooth models were subjected to cyclic fatigue loading amplitudes of 92 N accompanied by periodic QPD testing. Normal fit error values determined by QPD before loading and after fatigue cycling testing were recorded for the 3D simulated teeth. Results showed that location and depth of notch were important determinants of the number of cycles to crack initiation. The QPD device was able to monitor crack initiation and growth in at least three of the simulated teeth with accuracy. Although each tooth was found to reach failure at a different cycle number, the paired comparison was non-significant (p= 0.099) indicating results are comparable. Future analysis requires more simulated teeth to confirm these findings. Also, a comparison of the data obtained from 3D tooth models to natural extracted teeth as well as comparison to existing diagnostic tools used for crack identification would be warranted. These preliminary findings provide further evidence for the use of QPD as a diagnostic aid for early crack identification and monitoring structural integrity of teeth.