One of the fundamental tasks confronting engineers is the transmission and control of energy. The engineer, faced with this requirement and influenced by details of a specific, situation, his education and experience, and the customer's desires, will probably select a mechanical, electrical, or electro-mechanical system. Often a better choice exists—the use of a fluid power system. Fluid power systems employ pressurized fluids, liquids and/or gases, to transmit and control energy. Hydraulic systems use liquids, usually special oils or treated water. Pneumatic. systems use air or other gases. Both types are versatile and find a wide range of application.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering Johannesburg, September 2016 / The work in this dissertation presents the analysis of developing a novel means of flight trajectory alteration of a civil aircraft. Piezoelectric actuators have been advancing in the aerospace industry with uses in structural, vibrational and sensing applications. However, they have not been considered as a primary control method like an elevator, aileron and rudder. The analysis performed in this research involved developing an actuation model which is designed such that various changes in flight trajectory are brought about. The analysis began by building a base rigid aircraft model, where other analyses were appended to. The rigid aircraft model was developed using the aerodynamics of both Roskam (2001) and DATCOM. The DATCOM model was found to compensate for additional aircraft positions outside the flight envelope, whereas Roskam (2001) did not adequately provide the aerodynamics for when the aircraft would experience stall conditions, for example. The research then lead into developing the piezoelectric actuation model. This involved utilizing piezoelectric actuators on the wing of the aircraft, which was set to create vertical and twisting deformations, without altering the wing’s camber. Two novel methods of actuation are discussed. A wing - twist mode which consisted of three types of actuation, viz. linear twist, inverse linear twist, and linear twist symmetric. The second was the bending mode which altered the aircraft’s dihedral, and consisted of two types of actuation, viz. linear bending and linear bending symmetric. Effects of these two modes on the aerodynamics were depicted. Added to the overall model was the analysis of elastic aerodynamic effects. This was conducted by performing vibrational analysis on the individual components of the aircraft, viz. wing, horizontal tail and vertical tail. The results found that the elastic aerodynamic effects on the rigid model were significant only in lift. The rest were not significant because of the high frequency of the beams under consideration. Conclusively, the novel actuation methodology developed in this research yielded results demonstrating the viability of it being used above conventional methods such as elevator, rudder and ailerons. This was found by noting that various trajectory alterations were perceived without input from the conventional actuation methods. Increase in the rotational motions, as well as the translational motion was found, but did not cause any dynamic instabilities in the aircraft model. Thus, the actuation model was seen to operate well above the conventional methods, and situation specific uses were described for the actuation modes. These include uses in take-off and landing, cruise optimization and coordinated turns. / MT2017

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Chronic dehydration is an endemic problem for many population groups. Current methods of monitoring hydration status are invasive, time consuming, cannot be performed while exercising, and require lab resources. A proposed solution is a wearable, continuous, and non-invasive device that uses harm-free ultrasonic pulses to detect changes in tissue hydration status over time. Customer and engineering requirements were defined and used to guide the design process. Literature reviews were performed to identify essential information on dehydration, assess current methods, discover state of the art devices, and describe ultrasonic theory. Market research was performed to identify athletes as the target population group. An adjustable elastic nylon bicep band prototype was manufactured and the integration of more advanced components was proposed. The theoretical signal processing method used to detect hydration status was validated through initial tests with a prototype electrical system composed of a Teensy 3.1 board, two 18 kHz piezoceramic disc elements, and an Arduino/LabVIEW interface. Tests with aluminum, rubber, and sponge materials were performed to compare the signal response to propagation through materials with different acoustic properties and water contents. Finally, tests performed with dehydrated bovine muscle tissue revealed a statistically significant difference between hydrated and dehydrated tissue, a promising indication for future device refinement.

Recent advances in the complexity of in vitro biological systems have enabled new possibilities for "Organ-on-a-Chip" systems with greater physiological relevancy. Microphysiological Systems (MPS) represent one such advance which incorporates a sophisticated biological construct with a custom designed biological sensor. As the world grapples with grand challenges such as the Opioid Crisis, novel neural MPS offer a means to address both the safety and efficacy of alternative therapeutics, while potentially accelerating the bench-to-market timeframe for lifesaving addiction treatments. Investigations into custom microfabrication processes for such in vitro combinatorial biosensors are thus warranted. This Dissertation addresses the development of a 3D microelectrode array (MEA) biosensor, designed for integration with a custom peripheral-central nervous system, nociceptive circuit. For such Biological MicroElectroMechanical Systems (BioMEMS) sensors, the dielectric layer is crucial as an insulator and part of the cellular microenvironment. Nanoporous silicon dioxide (SiO2) represents an excellent material for this application, however, can be difficult to incorporate on polymer-based BioMEMS platforms. After development of the baseline 3D MEA platform that can integrate several sensing modalities on a single chip, the work presented in this Dissertation further establishes a novel polydopamine (PDA) mediated chemistry for nanoporous SiO2 / Polyethylene Glycol / Matrigel microenvironment definition. Dorsal Root Ganglion (DRG)/nociceptor and Dorsal Horn (DH) neural spheroids were then matured atop this 3D MEA platform, and spontaneous / evoked compound action potentials (CAPs) were successfully recorded during and at the 6-month timepoints. Lastly, inhibitory drug trials enabled confirmation of multi-part biological activity, indicative of the neural coculture that enables a novel 3D MEA-integrated neural 3D MPS, demonstrated for the first time to our knowledge, for long-term electrophysiological applications.

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