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Stress urinary incontinence refers to the unintentional leakage of urine, which is caused by weakening of, or damage to, urethral sphincters or pelvic floor muscles. Not only do the symptoms lead to physical discomfort or pain, but also the embarrassment and inconvenience significantly affects the quality of life, including social, familial, occupational, and sexual aspects. The use of inherently compliant and stretchable materials in soft robotics has driven a new class of biomedical devices which exhibit safe human interaction and embodied intelligent responses. This thesis focuses on the potential solutions for addressing the lack of occlusive pressure adaption in artificial urinary sphincter by employing soft robotic technologies. The research problem is decomposed into three different engineering topics: sensing, actuation, and control, which can correspond to receptors, muscles and the spinal cord or brain, respectively, in terms of human nervous system. For sensing, a stretchable sensor that can wirelessly measure various types of strain is developed, which can be used to remotely monitor physiological activities such as bladder volume or urethral pressure and provide essential information for feedback control. Regarding actuation, a new design of artificial urinary sphincter is proposed. It allows local urethral tissue to relax and potentially avoid ischemia, erosion or atrophy resulting from long-term compression. For control, a new approach of soft control and computing using liquid metal is investigated. The transformation from fluidic to electrical signals allows the device to respond to any sudden intra-abdominal pressure change and give extra support to the mid-urethra. In addition to the active modalities of sensing, actuation and control, an elastic artificial bladder is created which is more physically and physiologically similar to the proximal portion of the lower urinary tract system compared to the rigid funnel specified in the ISO standard, creating a novel platform for testing new catheters or artificial urinary sphincters. This thesis demonstrates different transformative soft technologies to solve the unmet health problems in urinary incontinence. The prototypes are experimentally characterised on the benchtop and demonstrate their functionalities, controllability, and the potential of being implanted. The combination of these technologies can lead to an active or passive pressure-adaptive device that can be compliant to physiological signals or user demands.

While fluidic elastomer actuators (FEAs) have been widely adopted for soft roboticsapplications showing potential for capabilities not achievable by their rigid counterparts, they have limited stiffness due to their innate compliance and cannot alter stiffness independently of their configuration on their own. Existing methods of combining FEAs with other mechanisms to achieve stiffness tunability limit the flexibility of the actuators and necessitate additional control inputs, or require energy to maintain higher stiffness and need onboard electronics, and may not work in the presence of electromagnetic fields. To address these limitations, this work proposes the use of supercooled liquid (sodium acetate trihydrate solution) as the multifunctional working fluid of FEAs to control both position and stiffness; we hypothesize that such fluid would be capable of both inflating the elastomer chambers while in liquid state and rapidly solidifying and stiffening the actuators. We investigate the mechanical properties of crystallized SAT samples and ways that they can be reinforced. Additionally, we analyze the stiffness of FEAs that use the supercooled SAT solution as their working fluid, highlighting the high degree of stiffness change (increase by 6.56 times) induced by the crystallization of the solution. Furthermore, we demonstrate the multifunctional manipulation and stiffness change of an FEA with minimal control inputs using supercooled SAT solution as the working fluid. The proposed mechanism is a new way to combine the high manipulability of FEAs with stiffness tunability and opens up new possibilities in designing soft robots and manipulators.

The emergence of mechanical metamaterials — which derive their properties primarily from the underlying architecture rather than the constituent material — has unleashed a new era of material design and functionalities. To fully materialize the promising potentials of metamaterials, it is crucial to develop versatile, scalable, and easy-to-fabricate methods that can both generate and tailor the underlying periodic architecture. To this end, we propose the use of kirigami — a popular recreational art of cutting and manipulating paper — as a platform to create periodicity and super-stretchability. Kirigami has become a design and fabrication framework for constructing metamaterials, robotic tools, and mechanical devices of vastly different sizes. In this dissertation, our target is to study the mechanical behavior --- mostly in the field of dynamics and kinematics--- of kirigami metamaterials and establish a framework for future studies. For the first time, our study focuses on wave propagation in a buckled kirigami sheet with uniformly distributed parallel cuts.When we apply an in-plane stretching force that exceeds a critical threshold, this kirigami sheet buckles and generates an out-of-plane periodic deformation pattern that can change the propagation direction of passing waves. That is, waves entering the buckled Kirigami unit cells through its longitudinal direction can turn to the out-of-plane direction. As a result, the stretched kirigami sheet shows wave propagation bandgaps in specific frequency ranges. We have two approaches toward manipulating the bandgap, 1) Tuning the bandgap by controlling the stretching displacement to change the distribution of cross-section of area and distribution of moment of inertia inside of the periodic unit cell of kirigami metamaterial and 2) programming stretched kirigami material by intentionally sequencing its constitutive mechanical bits. Such sequencing exploits the multi-stable nature of the stretched-buckled kirigami, which allows each mechanical bit to settle into two stable equilibria with different shapes (aka. “0” and “1” states). Therefore, by designing the sequence of 0 and 1 bits, one can fundamentally change the underlying periodicity of the kirigami and thus program the phononic bandgap frequencies. To this end, our study develops an algorithm to identify the unique periodicities using “n-strings” consisting of n mechanical bits.

Efficient and tube-traversing systems are needed. Hydraulically driven soft robots offer a solution to this problem where the maneuverability of soft robotics and the power density of hydraulic power transmission are both critical. This thesis presents the design, modeling, and manufacturing techniques for developing a multi-segment, hydraulically driven soft robot capable of traversing tubular environments like a burrow. A new force model was developed to address modeling limitations of the traditionally thin-walled, pneumatically-driven McKibben actuator – a common linear soft actuator. Hydraulic contracting and extending actuators were fabricated, and the new model was experimentally validated against commonly used existing models for both actuator versions. In the contracting McKibben experiments, the overall average error for the new model was 9.1% while the overall average error for three commonly used models were 9.9%, 10.5%, and 10.0%. Similar results were reported in the extending McKibben experiments. While the improvement of the new model over the other models is small, it is expected that the new model will be more accurate for high-pressure actuators with thicker walls that are needed in burrowing applications. One contracting actuator was driven at 13.9 MPa – the highest known pressure to date in literature. Further testing showed that extending McKibben actuators follow traditional column buckling theory, and it was demonstrated that extending McKibben actuators can develop extension forces greater than the critical buckling load when operating in a constrained environment such as a burrow. Radially expanding traction actuators were developed to generate the forces needed to anchor the multi-segment robot in the burrow. A new traction force model was developed to predict the generated traction force when actuated in a burrow. Multiple traction actuators were designed, fabricated, and experimentally tested to validate the model. The results of the experiments showed the new model to be a reasonable predictive design tool for the traction actuators. One extending McKibben and two traction segments were combined into a novel multi-segment robot with internal fluid lines allowing for independent actuation of the robot segments - enabling travel in both the forward and reverse directions. Experimental constraints, performance constraints, and performance objectives of the robot design were selected to ensure the robot could generate the forces and motions for efficient travel. A grid-search was used to study the solution space and select an initial geometry for the multi-segment robot within the constraints and objectives of the design. The extending McKibben segment was 76.2 mm long, had a 50.8 mm outside diameter, a 3.2 mm initial wall thickness, and was built with an initial fiber wrap angle of 80 degrees. When pressurized at 207 kPa, the extender could produce up to 206 N of extension force. The two traction segments had the same outside diameter, wall thickness, and operating pressure as the extending segment. The 114.3 mm long segments were able to produce up to 1043 N of traction force. The multi-segment robot was tested in two horizontally oriented tubes of varying diameters to simulate a burrow, and it was able to travel in both directions without issues. The robot was also tested in a vertical tube and was able to travel upwards against gravity. These results demonstrate that the contributions in this thesis provide the framework to develop soft robotic solutions for applications like burrowing where large forces and specific motions are required.

The objective of this thesis was to develop a novel bidirectional soft actuator for use in bioinspired and wearable robotic devices by investigating the effects that electromagnetic and material properties have on displacement. Findings from the thesis have the potential to significantly advance the field of soft robotics by demonstrating the viability of using elastomeric materials and magnetic fields as the driving mechanism for a new soft actuation method. The three primary aims were to develop uniform electromagnetic coils for actuation, to create soft cores to be combined with the electromagnetic coils to bolster the magnetic field and to study the displacement of the embedded assembly in an elastomeric material, effectively creating a soft solenoid capable of bidirectional actuation. In practice, this was a success. The winding process for coils was improved for creating uniform coils with a 3D printed winder and the cores were tested for their magnetic field strength based on varying weight fraction of particles. Two final actuators were made to test for differences in displacement based on mixing ratio changes in the material fabrication processes. Ecoflex 00-20, (Smooth-On Inc.: Macungie, PA) made using a 1A:1B mixing ratio, was found to perform approximately 25.2% better in compression and about 52.5% better in repulsion (based on average values) than the actuator made using a 1A:2B ratio. The final device was capable of average displacement values of 0.135 mm in compression and 0.158 mm in repulsion.

In this research, a novel pneumatic soft actuator for continuum robot arm has been designed, partially modeled and manufactured. The actuator is consisting of a single tube made of silicone rubber, some elastic rings around the tube that partially divide the tube into different sections and shape-memory alloy (SMA) springs that connects the rings to each other. By increasing pressure inside the tube, the tube starts inflating in a nonuniform manner due to the existence of the rings on the surface of the tube and the nonlinear behavior of the silicone rubber. By activating SMA springs on the surface of different sections of the tube, the inflated region on the tube will be controlled. The actuator has been manufactured and tested individually. To manufacture the tube, the commercial Eco-flex 030 epoxy has been used and been molded using commercially available Bic pens as a mold. The change in the behavior of the silicone rubber tube after adding each element to the tube has been studied to monitor the change in the nonlinear behavior of the tube. The SAM springs have been made by training nitinol wires from the Flexinol company into springform. The SMA springs properties have been calculated to match the required property of the system. The behavior of the resulted actuator has been studied both during actuation and deactivation of the SMA springs. To model the behavior of the actuator, the properties of silicon rubber has been extracted by conducting required mechanical tests. Later, by fitting the results to different hyperplastic models the behavior of Eco-flex 030 has been modeled. To choose the best model, the behavior of the silicone rubber tube trough changing in pressure has been simulated using Ansys. The material model with closest results to the actual experimental model have been chosen. Due to the nonlinearity of the silicone rubber, the volume-pressure change inside the tube exhibits instability in the related function which is the result of both the material property and the geometry of the system. This will result in instability and failure of the solver. Therefore, the comparison between the different models was made by comparing the instability pressure. The presented actuator has the advantage of needing less number of air supplies to have the same degree of freedom compared to the conventional pneumatic actuators, thanks to utilizing the instability of silicone rubber.

The design of the control and hardware systems for a robot intended for interaction with a human user can profit from a critical analysis of the human neuromotor system and human biomechanics. The primary observation to be made about the human control and ``hardware’’ systems is that they work well together, perhaps because they were designed for each other. Despite the limited force production and elasticity of muscle, and despite slow information transmission, the sensorimotor system is adept at an impressive range of motor behaviors. In this thesis I present three explorations on the manners in which the human and hardware systems work together, hoping to inform the design of robots suitable for human-robot interaction. First, I used the serial reaction time (SRT) task with cuing from lights and motorized keys to assess the relative contribution of visual and haptic stimuli to the formation of motor and perceptual memories. Motorized keys were used to deliver brief pulse-like displacements to the resting fingers, with the expectation that the proximity and similarity of these cues to the response motor actions (finger-activated key-presses) would strengthen the motor memory trace in particular. Error rate results demonstrate that haptic cues promote motor learning over perceptual learning. The second exploration involves the design of an actuator specialized for human-robot interaction. Like muscle, it features series elasticity and thus displays good backdrivability. The elasticity arises from the use of a compressible fluid while hinged rigid plates are used to convert fluid power into mechanical power. I also propose impedance control with dynamics compensation to further reduce the driving-point impedance. The controller is robust to all kinds of uncertainties. The third exploration involves human control in interaction with the environment. I propose a framework that accommodates delays and does not require an explicit model of the musculoskeletal system and environment. Instead, loads from the biomechanics and coupled environment are estimated using the relationship between the motor command and its responses. Delays inherent in sensory feedback are accommodated by taking the form of the Smith predictor. Agreements between simulation results and empirical movements suggests that the framework is viable.