▼ This was a co-author thesis done by Taylor Dunn and Adam Smith Abstract: A stair stretcher is a medical transportation device specifically designed to negotiate a staircase. The current market available products require significant physical effort of use by emergency personnel and lack in patient safety. To design a better system the engineering design processes was used to design and develop an improved prototype system. The group first gained and understanding of the market and potential improvements by researching into patents, standards, professional advice, and the business markets. From this research the group formed developed a list of design priorities to be executed by the design plan. By understanding customer’s needs and with thorough engineering analysis the group redesigned an improved stair chair prototype via improvement of six main sub-systems: motor and drive system, back rests, arm rests, restraints, leg rests, and the overall chair frame. Each sub-system was designed to enhance the chair’s functionality and to make a product solution that is superior to the current stair chairs on the market. The chair prototype was then assembled for testing and verification of design potential. Advisors/Committee Members: Setlock, Robert.

▼ Magnetorheological elastomers (MREs) are an emerging branch within the smart materials field that consists of hard or soft magnetic particles embedded in a rubber compound. Current applications and research have been focused on changing the stiffness of these materials by applying an external magnetic field. Components of vibration absorbers and base isolation systems that employ this material have shown the capability of offering improved performance over conventional solutions. These particular applications use soft magnetic material; however, MRE materials containing hard magnetic filler materials (those that remain permanently magnetized) were the primary focus of this project and are referred to as H-MREs. When a magnetic field is applied perpendicularly to these particles, the filler particles generate a net torque and these samples can be used as a controlled actuator. Preliminary work has been conducted to characterize these H-MREs (since their properties are significantly different than “soft” MREs) and this work has shown their usefulness in engineering applications. However, unlike comparable smart materials such as piezoelectrics and electroactive polymers (EAP), additional modeling and experimentation needs to be conducted in order to develop usable models and better understand their behavior. The first portion of this paper focuses on developing experimental models to predict the behavior of H-MRE materials as cantilevered beam actuators for use in future applications. Two additional, newer applications for which H-MREs could be useful are energy harvesting and sensing. Sensors are utilized almost everywhere today as they are used to monitor the performance of a system (whether it is fluid flow, vibration measurements, etc.). Piezoelectric materials, those that respond to electric stimuli, and Galfenol, an engineered material similar to MREs, have been studied extensively for their application as self-sensing actuators. It is hypothesized that H-MREs could be used in a similar capacity by developing a way to monitor the displacement of the material using a magnetic circuit. Based on a similar principle, energy harvesting involves the conversion of one form of energy (kinetic, solar, etc.) into a more storable form. Previous research has been conducted using other smart materials in this capacity and it is also hypothesized that H-MREs could be used in a similar capacity by capturing energy from mechanical vibrations and storing it in the form of electrical energy/power using a specialized circuit and the same principles discussed above. The primary goal of the second portion of this project will be to determine the feasibility of using H-MREs in the capacity of energy harvesting and sensing technologies. This feasibility study includes the development of experiments to assess these capabilities and the implementation of the experiments for verification of the predicted behavior. Finally, much consideration is given to work that will need to be done in the future in order to fully understand the behavior of these materials and allow them to be implemented in future relevant applications. Advisors/Committee Members: Koo, Jeong-Hoi.

▼ This thesis investigates the factors influencing bone remodeling within the human skeleton with a focus on developing methods for constructing prosthetic bone scaffolds containing cells to progenerate into living bone upon implantation in the body. These porous scaffolds would ideally regulate events such as cellular proliferation and intracellular signaling after surgical implantation. The overarching goal is to identify materials, geometries, and other properties of the scaffold design in order to generate replacement tissue that replicates the original bone structure and geometry.Bone remodeling is the process of simultaneous removal of old bone and replacement with new bone powered by the coupled actions of osteoclasts and osteoblasts, cells that resorb bone and produce bone, respectively. While bone remodeling occurs more intensely during skeletal development, it continues throughout a human's lifetime, repairing microscopic damage resulting from stress and fatigue on the body. There are many different models that describe how remodeling may occur as well as what initiates the remodeling response to damaged bone. Historically, biologists explored tissue development primarily in terms of chemical and electrical signal pathways controlled by genes. However, recently published studies have implied that bone cells may be able to sense and react to mechanical forces. These forces likely have a crucial role in stimulating remodeling to occur based on the existing three-dimensional geometry of the bone and how well suited it is to handle the forces. Many independently published studies have investigated singular mechanical factors in the stimulation of bone remodeling as well as the resulting implications for the design of implanted skeletal scaffolds. However there remains a lack of publications that analyze multiple studies in order to examine their similarities and discrepancies. Reviews linking multiple studies are valuable tools for moving bone engineering theories into practical realities. Based on the hypothesis that stresses that develop among bone cells are control mechanisms in regulating bone remodeling, a literature search was conducted. Two critical factors were examined in detail: the effects of pore geometry and the stiffness of the substrate on the rate and concentration of cell proliferation. Experimental results of conducted studies as well as theoretical results using finite element analysis and analytical equations were compared and contrasted. Finally, conclusions were synthesized from each study into general observations that are important to the future creation of bone scaffolds. Advisors/Committee Members: Setlock, Mr. Robert.

▼ Please note: This is a co-authored thesis by two honors students, Adam Smith and Taylor Dunn. ABSTRACT By Adam Smith and Taylor Dunn Development of an Improved Medical Transport Device: Stair Chair A stair stretcher is a medical transportation device specifically designed to negotiate a staircase. The current market available products require significant physical effort of use by emergency personnel and lack in patient safety. To design a better system the engineering design processes was used to design and develop an improved prototype system. The group first gained and understanding of the market and potential improvements by researching into patents, standards, professional advice, and the business markets. From this research the group formed developed a list of design priorities to be executed by the design plan. By understanding customer’s needs and with thorough engineering analysis the group redesigned an improved stair chair prototype via improvement of six main sub-systems: motor and drive system, back rests, arm rests, restraints, leg rests, and the overall chair frame. Each sub-system was designed to enhance the chair’s functionality and to make a product solution that is superior to the current stair chairs on the market. The chair prototype was then assembled for testing and verification of design potential. Advisors/Committee Members: Setlock, Robert.

▼ The viscoelastic material models are often frequency dependent hence the dynamic behavior of such materials is characterized by the associated non-linear eigenvalue problems. Traditionally these eigenvalue problems are formulated in state-space form via first order realization of the frequency domain equations to time domain. However, such transformation leads to a large matrix eigenvalue problem, which depends upon number of internal parameters used for approximating the material behavior, and hence they can be computationally expensive. Moreover, the state-space formulation does not provide physical insight of the original coordinates which may be used for measurement and control purposes. In this research, it is shown that by solving the associated transcendental eigenvalue problems, these frequency dependent eigenvalue problems can be solved without state-space realization. With a few numerical examples, the eigenvalues computed by the proposed method are compared with those obtained in the traditional state-space methods. By preserving the dynamics behavior in the frequency domain, it is also shown that the physical parameters (especially damping and stiffness) of the material can be modified by active means (active control). Such modification utilizes frequency response receptance functions, which may be extracted during dynamic experiments. Active modification strategy may be used to alter the material behavior during its operation and may be instrumental in developing more advanced viscoelastic materials. Advisors/Committee Members: Singh, Kumar.