Soft robots currently rely on additional hardware such as pumps, high voltage supplies,light generation sources, and magnetic field generators for their operation. These components resist miniaturization; thus, embedding them into small-scale soft robots is challenging. This issue limits their applications, especially in hyper-redundant mobile robots. This dissertation aims at addressing some of the challenges associated with creating miniature, untethered soft robots that can function without any attachment to external power supplies or receiving any control signals from outside sources. This goal is accomplished by introducing a soft active material and a manufacturing method that together, facilitate the miniaturization of soft robots and effectively supports their autonomous, mobile operation without any connection to outside equipment or human intervention. The soft active material presented here is a hydrogel based on a polymer called poly(Nisopropylacrylamide) (PNIPAAm). This hydrogel responds to changes in the temperature and responds by expanding or contracting. A major challenge regarding PNIPAAm-based hydrogels is their slow response. This challenge is addressed by introducing a mixedsolvent photo-polymerization technique that alters the pore structure of the hydrogel and facilitates the water transport and thus the rate of volume change. Using this technique, the re-swelling response time of hydrogels is reduced to 2:4min – over 25 times faster than hydrogels demonstrated previously. The material properties of hydrogels including their response rate and Young’s modulus are tuned simultaneously. The one-step photopolymerization using UV light is performed in under 15 sec, which is a significant improvement over thermo-polymerization, which takes anywhere between a few minutes to several hours. Photopolymerization is key towards simplifying recipes, improving access to these techniques, and making them tractable for iterative design processes. To address the manufacturing challenges, soft voxel actuators (SVAs) are presented. SVAs are actuated by electrical currents through Joule heating. SVAs weighing only 100 mg require small footprint microcontrollers for their operation which can be embedded in the robotic system. The advantages of hydrogel-based SVAs are demonstrated through different robotic platforms namely a hyper-redundant manipulator with 16 SVAs, an untethered miniature robot for mobile underwater applications using 8 SVAs, and a gripper using 32 SVAs.

In the present study, primarily, gas diffusion layer samples containing microporous layers (MPLs), are fabricated using carbon paper substrate, PUREBLACK® carbon powder and polyethylene glycol (PEG) as pore forming agent. The GDLs are studied in single cell fuel cell, to evaluate the effect of porosity of the micro-porous layer on the performance at different operating relative humidity conditions and compared with commercial GDLs. Scanning electron microscopy (SEM) and contact angle measurements indicate crack-free surface morphology and hydrophobic characteristics of the PUREBLACK® based GDLs, respectively. By varying the wt. % of PEG, fuel cell performance is evaluated under relative humidity conditions of 60 and 100 % using H2/O2 and H2/Air at 70 oC and the durability is also evaluated for the samples without, with 30% PEG and commercial. The fuel cell performance of the GDL with 30 % PEG (with pore volume 1.72 cc.g-1) exhibited higher performance (444 and 432 mW.cm-2 at 60 and 100 % RH conditions, respectively using H2 and air) compared to that without pore forming agent (436 and 397 mW.cm-2).Subsequently, the best performing configuration underwent two different ex-situ methods of accelerated stress testing (AST), in water and hydrogen peroxide (30%), for 1000 and 24 h, respectively. The samples were evaluated via contact angle, SEM, and fuel cell performance, before and after the ASTs, and compared to similar configuration, using carbon powder VULCAN® (XC-72R), and aged in the exact same conditions. Contact angle and SEM demonstrated greater degradation of VULCAN® carbon, especially in hydrogen peroxide, where carbon corrosion caused surface cracks and change in hydrophobicity. The fuel cell performance and durability, evaluated at 60 and 100% RH at 70 oC, using O2 and air as oxidants, confirmed that VULCAN® carbon is more prone to carbon corrosion, with significant performance loss (12-19%) in contrast to PUREBLACK® that demonstrated higher carbon corrosion resistance due to its graphitized surface.

Honeycomb sandwich panels have been used in structural applications for several decades in various industries. While these panels are lightweight and rigid, their design has not evolved much due to constraints imposed by available manufacturing processes and remain primarily two-dimensional extrusions sandwiched between facings. With the growth in Additive Manufacturing, more complex geometries can now be produced, and advanced design techniques can be implemented into end use parts to obtain further reductions in weight, as well as enable greater multi-functionality. The question therefore is: how best to revisit the design of these honeycomb panels to obtain these benefits?

In this work, a Bio-Inspired Design approach was taken to answer this question, primarily since the hexagonal lattice is so commonly found in wasp and bee nests, including the well-known bee’s honeycomb that inspired these panel designs to begin with. Whereas prior honeycomb panel design has primarily focused on the hexagonal shape of the unit cell, in this work we examine the relationship between the various parameters constituting the hexagonal cell itself, specifically the wall thickness and the corner radius, and also examine out-of-plane features that have not been previously translated into panel design. This work reports findings from a study of insect nests across 70 species using 2D and 3D measurements with optical microscopy and X-ray tomography, respectively. Data from these biological nests were used to identify design parameters of interest, which were then translated into design principles. These design principles were implemented in the design of honeycomb panels manufactured with the Selective Laser Sintering process and subjected to experimental testing to study their effects on the mechanical behavior of these panels.

In large modern urban areas, traffic congestion and fatality have become two serious problems. To improve the safety and efficiency of ground mobility, one promising solution is the cooperative control of connected and automated vehicle (CAV) systems, which can avoid human drivers’ incapability and errors. Taking advantage of two-dimensional (2D) vehicular control, this dissertation intends to conduct a thorough investigation of the modeling, control, and optimization of CAV systems with flocking control. Flocking is a dynamic swarm congregating behavior of a group of agents with self-organizing features, and flocking control of CAV systems attempts to achieve the maintenance of a small and nearly constant distance among vehicles, speed match, destination cohesion, and collision and obstacle avoidance.

Concerning artificial multi-agent systems, such as mobile robots and CAV systems, a set of engineering performance requirements should be considered in flocking theory for practical applications. In this dissertation, three novel flocking control protocols are studied, which consider convergence speed, permanent obstacle avoidance, and energy efficiency. Furthermore, considering nonlinear vehicle dynamics, a novel hierarchical flocking control framework is proposed for CAV systems to integrate high-level flocking coordination planning and low-level vehicle dynamics control together. On one hand, using 2D flocking theory, the decision making and motion planning of engaged vehicles are produced in a distributed manner based on shared information. On the other hand, using the proposed framework, many advanced vehicle dynamics control methods and tools are applicable. For instance, in the low-level vehicle dynamics control, in addition to path trajectory tracking, the maintenance of vehicle later/yaw stability and rollover propensity mitigation are achieved by using additional actuators, such as all-wheel driving and four-wheel steering, to enhance vehicle safety and efficiency with over-actuated features.

Co-simulations using MATLAB/Simulink and CarSim are conducted to illustrate the performances of the proposed flocking framework and all controller designs proposed in this dissertation. Moreover, a scaled CAV system is developed, and field experiments are also completed to further demonstrate the feasibility of the proposed flocking framework. Consequently, the proposed flocking framework can successfully complete a 2D vehicular flocking coordination. The novel flocking control protocols are also able to accommodate the practical requirements of artificial multi-agent systems by enhancing convergence speed, saving energy consumption, and avoiding permanent obstacles. In addition, employing the proposed control methods, vehicle stability is guaranteed as expected.

The fuel cell is a promising device that converts the chemical energy directly into the electrical energy without combustion process. However, the slow reaction rate of the oxygen reduction reaction (ORR) necessitates the development of cathode catalysts for low-temperature fuel cells. After a thorough literature review in Chapter 1, the thesis is divided into three parts as given below in Chapters 2-4.

Chapter 2 describes the study on the Pt and Pt-Me (Me: Co, Ni) alloy nanoparticles supported on the pyrolyzed zeolitic imidazolate framework (ZIF) towards ORR. The Co-ZIF and NiCo-ZIF were synthesized by the solvothermal method and then mixed with Pt precursor. After pyrolysis and acid leaching, the PtCo/NC and PtNiCo/NC were evaluated in proton exchange membrane fuel cells (PEMFC). The peak power density exhibited > 10% and 15% for PtCo/NC and PtNiCo/NC, respectively, compared to that with commercial Pt/C catalyst under identical test conditions.

Chapter 3 is the investigation of the oxygen vacancy (OV) effect in a-MnO2 as a cathode catalyst for alkaline membrane fuel cells (AMFC). The a-MnO2 nanorods were synthesized by hydrothermal method and heated at 300, 400 and 500 ℃ in the air to introduce the OV. The 400 ℃ treated material showed the best ORR performance among all other samples due to more OV in pure a-MnO2 phase. The optimized AMFC electrode showed ~ 45 mW.cm-2, which was slightly lower than that with commercial Pt/C (~60 mW.cm-2).

Chapter 4 is the density functional theory (DFT) study of the protonation effect and active sites towards ORR on a-MnO2 (211) plane. The theoretically optimized oxygen adsorption and hydroxyl ion desorption energies were ~ 1.55-1.95 eV and ~ 0.98-1.45 eV, respectively, by Nørskov et al.’s calculations. All the configurations showed oxygen adsorption and hydroxyl ion desorption energies were ranging from 0.27 to 1.76 eV and 1.59 to 15.0 eV, respectively. The site which was close to two Mn ions showed the best oxygen adsorption and hydroxyl ion desorption energies improvement with the surface protonation.

Based on the results given in Chapters 1-4, the major findings are summarized in Chapter 5.

Commercial Li-ion cells (18650: Li4Ti5O12 anodes and LiCoO2 cathodes) were subjected to simulated Electric Vehicle (EV) conditions using various driving patterns such as aggressive driving, highway driving, air conditioning load, and normal city driving. The particular drive schedules originated from the Environment Protection Agency (EPA), including the SC-03, UDDS, HWFET, US-06 drive schedules, respectively. These drive schedules have been combined into a custom drive cycle, named the AZ-01 drive schedule, designed to simulate a typical commute in the state of Arizona. The battery cell cycling is conducted at various temperature settings (0, 25, 40, and 50 °C). At 50 °C, under the AZ-01 drive schedule, a severe inflammation was observed in the cells that led to cell failure. Capacity fading under AZ-01 drive schedule at 0 °C per 100 cycles is found to be 2%. At 40 °C, 3% capacity fading is observed per 100 cycles under the AZ-01 drive schedule. Modeling and prediction of discharge rate capability of batteries is done using Electrochemical Impedance Spectroscopy (EIS). High-frequency resistance values (HFR) increased with cycling under the AZ-01 drive schedule at 40 °C and 0 °C. The research goal for this thesis is to provide performance analysis and life cycle data for Li4Ti5O12 (Lithium Titanite) battery cells in simulated Arizona conditions. Future work involves an evaluation of second-life opportunities for cells that have met end-of-life criteria in EV applications.