Many natural systems interact with the interface between air and liquids on a daily basis. Plants like the lotus that have self-cleaning leaf surfaces and animals that intake fluids in a variety of ways are all examples of these systems. Plants and animals exploit interfacial fluid dynamics in a variety of ways to survive in numerous harsh environments. In this thesis, five studies, inspired by natural interactions with interfaces are presented. The first study explores the influence of surface wettability in the dynamics of beams struck by water droplets. This study is inspired by raindrop-leaf interaction in nature. We characterize beam behavior after impact using a simple ODE and also find that a hydrophobic cantilever experiences reduced average torque over time than a cantilever with a hydrophilic surface. In the second study we investigate the fluid dynamics of how dogs lap water with their tongue. Dogs lap because they have incomplete cheeks and cannot suck. When lapping, a dog's tongue pulls a liquid column from the bath, suggesting that the hydrodynamics of column formation are critical to understanding how dogs drink. We measured lapping in nineteen dogs and used the results to generate a physical model of the tongue's interaction with the air-fluid interface. These experiments help to explain how dogs exploit the fluid dynamics of the generated column. The results demonstrate that effects of acceleration govern lapping frequency, which suggests that dogs curl the tongue to create a larger liquid column. Comparing lapping in dogs and cats reveals that, despite similar morphology, these carnivores lap in different physical regimes: a high-acceleration regime for dogs and a low-acceleration regime for cats. In the third study how bats drink on the wing is investigated. Bats are unique in nature in that they are one of the only animals that ingest fluids during non-hovering flight. This behavior has the advantage that bats can drink and maintain flight while hunting for food. We find that bats simply extend the tongue and drag it on the water surface while flying. The bats ingest water that coats the inside of the mouth and tongue after removal from a water bath. Bats also change their wing-beat pattern to avoid hitting the water. We investigate the crown splash instability formed when a rounded rod impacts a fluid bath. The crown splash has been widely studied; however, it has not been seen in the configuration we present. When a rounded rod impacts water, it displaces fluid, and that fluid forms a lamella that climbs up the side of the rod. Depending on the speed of impact, rod size, and other fluid parameters an instability similar to a crown splash forms. In this study, we characterize the growth of the fluid lamella along with the wavelength of the instability. Finally, we investigate the dynamics of squeezed fluids inspired by clapping wet hands. When water splashes, numerous water droplets, rather than fluid threads, are dispersed. This squeezing motion of the hands makes the fluid in between eject and eventually break into drops. In this study, the trajectory of a rim formed by fluid squeezed between two plates is measured and captured by a theoretical model. Additionally, the spacial distribution of the rim perturbation is predicted using Rayleigh-Plateau instability theory. / Ph. D.

Generating accurate simulations of the forces in the Glenohumeral joint is essential for investigation of normal and pathologic Shoulder function. It forms the basis for evaluating fracture treatment, joint replacement design and fixation. However, due to its complex anatomy and large range-of-motion, measuring the dynamic in-vivo forces and kinematics of the Glenohumeral joint remains a challenging problem in the field of biomechanics. This study shows the development and validation of a new testing medium for the Glenohumeral joint. The study uses a combined approach of in-vitro and in-silico testing and validates against previous data. This is achieved using a mechanical testing rig and finite element model which both closely represent the in-vivo Glenohumeral physiological characteristic including; geometry, muscular loading patterns, joint range-of-motion and external loadings. The mechanical model uses two instrumented implants based on current gold standard in-vivo testing. The two head types used are a Stem implant and a resurfacing head type implant. Comparison is made between the two head types as testing mediums for in-vitro testing. It is shown the resurfacing head more closely maintains the natural properties of the bone. Testing displays the significant advantages of in-vitro and in-silico testing over in-vivo testing. Validation is achieved by comparing simulated functional movements and activities of daily living to previous published data. When compared with previous data, recorded results from the mechanical testing rig shows high conformity. Comparison shows -3.95% and 4.14% error during 45° abduction with the resurfacing and stem implants respectively. Activities of daily living display similar loading patterns but lower maximum recorded force agreement. This has highlighted problems with unpredictable and complex muscular combinations when assessing complex movements. FE results show similar loading patterns and stress areas to previous data but record lower maximum forces than previous in-vivo data. Force and stress results from the FE model highlight the significant force increase external loads apply to the joint complex. Cross-validation between the mechanical testing rig and FE model shows high conformity and similar loading patterns. The developed medium is shown to be successfully validated against “gold standard” in-vivo data and other previous studies. Research experiments are used to illustrate the variety of testing possible with the developed medium and to further develop and validate the design. Research into trauma, injury and fixation is discussed and joint forces measured. This data lays a foundation for future testing using the developed test medium. The testing medium provides repeatable and reproducible results for forces within the Glenohumeral joint. This can now be used to further understand joint kinematics, injuries, fracture prorogation and fixation. It will also provide a valuable training aid for a complex joint. Better understanding, testing and training of new techniques, tools and traumas is now possible. This will aid in reducing injury prevalence, severity, healing time and ultimately improving patient quality of life.

Nowadays, almost all existing wheelchairs have the problem that they only satisfy the disabled people to use for normal moving and transportation. A new wheelchair with a gear system guide rail which installed in the car is presented in this paper. The gear guide rail system will transport the whole wheelchair and person on it into the car. This wheelchair system will help people with disability whatever passengers or drivers to get into cars automatically. In this paper, the operation and the strength will be analysed through 3D model and theoretical calculations. Surveying to Swedish market, Volvo XC60 and V60 is chosen to design the size of the wheelchair. Besides, this new wheelchair system also can be suitable for the cars which are larger than those two car models.

Innovative multifunctional materials are essential to many new sensor applications. Piezoresistive nano-composites make up a promising class of such materials that have the potential to provide a measurable response to strain over a much wider range than typical strain gages. Commercial strain gages are currently dominated by metallic sensors with a useable range of a few percent strain at most. There are, however, many applications that would benefit from a reliable wide-range sensor. These might include the study of explosive behavior, instrumentation of flexible components, motion detection for compliant mechanisms and hinges, human-technology interfaces, and a wide variety of bio-mechanical applications where structural materials may often be approximated as elastomeric. In order to quantify large strains, researchers often use optical methods which are tedious and difficult. This thesis proposes a new material and technique for quantifying large strain (up to 40%) by use of piezoresistive nano-composite strain gages. The nano-composite strain gage material is manufactured by suspending nickel nano-strands within a biocompatible silicone matrix. Study and design iteration on the strain gage material requires an improved understanding of the electrical behavior and conduction path within the material when strained. A percolation model has been suggested for numerical approximations, but has only provided marginal results for lack of data. Critical missing information in the percolation model is the nano-strand cluster size, and how that size changes in response to strain. These data are gathered using a dynamic technique in the scanning electron microscope called voltage contrast. Cluster sizes were found to vary in size by approximately 6% upon being strained to 10%. A feasibility study is also conducted on the nano-composite to show its usability as a strain gage. High Displacement Strain Gages (HDSGs) were manufactured from the nano-composite. HDSGs measured the strain of bovine ligament under prescribed loading conditions. Results demonstrate that HDSGs are an accurate means for measuring ligament strains across a broad spectrum of applied deformations.

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