This work is a “sandwich” thesis, containing the work of 4 manuscripts studying droplet motion preceded by background chapters. We start with an introduction that focuses on general concepts in capillarity and fluid dynamics, and how we can build scaling models from first principles. Following the introduction, there is a methodology chapter which provides some notes on the experimental methods used in the manuscripts. In the first manuscript (chapter 3) we look into how a moving a droplet leads to dissipation in an underlying underlying soft substrate. We develop a system of sub-micron elastomeric substrates as well as micropipette based technique to study the forces on micrometric droplets in motion. We find that dissipation scales with the thickness of the underlying film. In chapter 4, we follow up the work on dissipation in soft substrates with a study on the role of uncrosslinked chains in the same substrates, as well as providing more details on substrate fabrication. Next, in chapter 5 we study how geometry can be used to drive motion in droplets. We suspend droplets between two fibers held at an angle and find droplets move towards the apex of the fibers. We develop a simple scaling model for the motion and we are able to modify the fibers to develop a droplet pump that allows for long range microdroplet transport. In the final manuscript (chapter 6) we study how external forces can be used to drive droplet motion. In particular, we study how magnetic fields can drive rearrangements in an aggregate of ferrofluid droplets. We describe phase changes in such a system with a simple scaling model. In these works we develop an understanding of how to drive motion in droplets, with an impact on both fundamental physics and applications in industry. / Thesis / Doctor of Philosophy (PhD) / From cactus needles using their needles to collect water droplets, to microfluidic devices used for health sensing, the motion of droplets is ubiquitous in both nature and industrial applications. In this work, we use experiments and simple models to understand the motion of microscopic droplets across a variety of systems. We first look at how energy is lost in these systems, in particular dissipation in droplets moving across a soft substrate. We then look at how we can use geometry and capillarity to drive motion in droplets by moving droplets with fiber pairs. Finally we use ferrofluids to study the effect of external driving forces on clusters of droplets.

A method of using optical fiber to measure strain and correct for the effects of temperature is proposed. A means of measuring apparent strain is given, pure temperature is measured using Fresnel-backscatter based Optical Time Domain Reflectometry, and a method for combining the two measurements to obtain a measurement of mechanically-induced strain alone is developed. The background, theory and experimental results that demonstrate the feasibility of such a system are presented and the results are compared with the performance of existing fiber-based means of measuring temperature. Experiments on several OTDR-addressed, intensity-based optical temperature sensors are performed and a method for manufacturing small air gap splices for use in measuring strain at several places along an optical fiber are presented. / Master of Science

The use of fiber reinforced plastics (FRP) in repairing and strengthening bridges has been researched in recent years. In particular, attaching unidirectional FRP to the tension face of reinforced concrete beams has provided an increase in stiffness and load capacity of the structure. However, due to the brittle nature of the unidirectional FRP, the ductility of the beam decreases. One possible solution to this problem is the use of cross-ply or off-axis FRP laminates. This thesis focuses on the investigation of the flexural behavior of reinforced concrete beams strengthened with one of two different FRP orientations (0°/90° and ±45°). More particularly, the change in strength and ductility of the beams as the number of FRP layers are altered is investigated. Seven under-reinforced concrete beams were constructed and tested to failure. With the exception of the control beam, each specimen was applied with two, three, or four layers of either 0°/90° and ±45° FRP orientations. To predict the flexural behavior of the specimens, a theoretical model was derived using basic concepts, past research, and the tested properties of the concrete, steel reinforcement, and FRP. Also, two methods were used to analyze the ductility of the tested beams. Along with the test details of each specimen; the moment, deflection, CFRP strain, crack patterns, and mode of failure are discussed. The results included an increase in load capacity with respect for the number of CFRP layers applied for both orientations. Also, the ductility of the beams were reduced by adding CFRP orientations. / Master of Science

Axial strain effects in multimode fibers are studied. A few-mode fiber is mounted on a tensile testing machine and strained at various speeds. The output of a monochromatic light source passing through it is monitored and recorded. Relations are noted between the light output the magnitude of tension and the rate of the applied axial strain. Flexural behavior of the optical fiber at various tensions is also studied by monitoring the modal output pattern. Relations are compiled to serve as a beginning to model these and other related modal effects. A theoretical background is also suggested to explain the observed effects. / Master of Science

The concept of incorporating optical fiber delay lines as signal processors is investigated. These signal processors are discrete-time filters implemented using optical fiber delay lines in the form of optical fiber couplers advantages of such a filter include the ability to eliminate the need for electro-optical conversion or at least postpone the conversion to a point where the electronics may be simplified. In addition, these optical signal processors exhibit all the advantages afforded traditional optical fiber systems. Furthermore, these devices allow high-speed signal processing rates greater than 1GHZ which rival the performance of the most advanced electronic counterparts available today. In this thesis, optical signal processors are investigated in detail. First, the fundamental signal processing concepts and optical component background is discussed for the analysis of the devices are developed. Subsequently, various configurations of optical signal processors are discussed and novel computer models for these configurations using Z-transform theory are presented. Lastly, experimental verification is presented of the rudimentary models and a unique approach is presented that will allow the creation of optical signal processors with a flexibility never achievable before. / Master of Science

A single piece of optical fiber can be utilized to sense both strain and temperature simultaneously. To develop such a sensor, we sandwich a section of two-mode elliptical core (e-core) fiber between two partially reflecting mirrors. This configuration can be considered as an intrinsic Fabry-Perot interferometer, in which the two-mode, e-core fiber serves as the resonant cavity. Two different types of phase modulation can be extracted under perturbations of strain and temperature on the fiber. These phase changes are due to the two-mode interference and intrinsic Fabry-Perot interference, respectively. The relationship between the phase information and the two physical measurands, i.e. strain and temperature, can be established using two coupled equations, in which the strain and temperature are considered as two unknowns. By solving these two coupled equations, we can simultaneously determine the strain and temperature. The waveguide theory and the Cross sensitivity analysis of this sensor are presented. The descriptions of four independent experiments that have been used to determine the coefficients of the two coupled equations are given. The resolutions of the strain and temperature measurements have been obtained to be 31 μm/m and 4.5 °C, respectively. / Master of Science

Methods designed to improve the practicality of the elliptical-core two-mode optical fiber sensors for use in real-life applications are presented. The improvements include the development of insensitive lead fibers and an optical device which allows fringe counting at the output of the sensor. The insensitive leads eliminate extraneous perturbations and effectively isolate the sensing region. The fringe counting optics are designed to generate quadrature-phase shifted signals, thereby allowing the determination of whether the strain is increasing or decreasing. Work performed to advance the understanding of the effect of sensor placement within a composite specimen is also presented. Optical fiber sensors are embedded between different laminae of a graphite-epoxy composite panel, and the outputs of the sensors are shown to be proportional to the distance of the sensor from the neutral axis. / Master of Science

This work concentrates on the study, analysis, and development of rare-earth-based optical fiber active devices. The properties of the neodymium ion are analyzed and related to its potential role in the operation of various active optical devices. Existing technology in rare-earth-based fiber amplifiers is reviewed. Novel techniques for the fabrication of rare-earth-based glass rods and fibers are presented. Further, a discussion of results and ideas for the point sensing of temperature, and the simultaneous sensing of temperature and strain using optical time-domain reflectometry techniques with such devices is also presented. / Master of Science

The objective of this thesis is to demonstrate the feasibility of developing holograms in the cladding region of an optical fiber. The cladding is first stripped and replaced with dichromated gelatin ( DCG ) which is a highly efficient holographic storage medium. The evanescent field of the fiber is used as the reference beam to form an interference pattern with an object wave. The interference of the two fields is recorded in the DCG and forms the hologram. The holograms recorded have a grating type structure and can be utilized for guiding light selectively in and out of the fiber. / Master of Science

Yes / Cells migrating over 2D substrates are required to polymerise actin at the leading edge to form lamellipodia protrusions and nascent adhesions to anchor the protrusion to the substrate. The major actin nucleator in lamellipodia formation is the Arp2/3 complex, which is activated by the WAVE regulatory complex (WRC). Using inducible Nckap1 floxed mouse embryonic fibroblasts (MEFs), we confirm that the WRC is required for lamellipodia formation, and importantly, for generating the retrograde flow of actin from the leading cell edge. The loss of NCKAP1 also affects cell spreading and focal adhesion dynamics. In the absence of lamellipodium, cells can become elongated and move with a single thin pseudopod, which appears devoid of N-WASP. This phenotype was more prevalent on collagen than fibronectin, where we observed an increase in migratory speed. Thus, 2D cell migration on collagen is less dependent on branched actin.