Due to their extraordinary material properties, epoxy has been widely used in various industries. Moreover, nanomaterials are infused into epoxy to enhance their mechanical performance and for encoding different functionalities, such as for fiber reinforced polymer (FRP) composites. However, additives in the epoxy matrix can affect curing and the mechanical properties of FRP structures. Therefore, the main objective of this thesis was to investigate the use of electrical capacitance tomography (ECT) for monitoring curing and subsurface damage in pristine epoxy and nanocomposite epoxy. In short, ECT uses a set of noncontact electrodes and interrogates a sensing area using different patterns of electric field excitations. Boundary capacitance measurements obtained simultaneously are used as inputs for solving the ECT inverse problem to reconstruct the electrical permittivity distribution of the sensing area. The hypothesis was that curing and damage of epoxy would result in permittivity changes that could be detected and localized by ECT. The thesis first starts with a detailed description of the ECT theory and system. Second, to test the hypothesis, pristine epoxy was subjected to ECT for monitoring curing, which was then validated using ultrasonic wave tests. Then, ECT was used to monitor the curing of carbon nanotube-based epoxies whose electrical properties are sensitive to strain. Both pristine and nanocomposite epoxy results confirmed the hypothesis that permittivity decreased with increasing curing time, and ECT can be used as a noncontact and noninvasive curing monitoring tool. Last, epoxy specimens with different geometries were drilled with holes to simulate damage. The results indicated that ECT was not only able to reconstruct the shape of the specimens but was also able to identify the location and severity of damage.

Soft robotics is a promising field that can solve several limitations of traditional rigid robotics. These systems are composed of soft and flexible materials to achieve high degrees-of-freedom and compliance with their surroundings. An important part of soft robotics is developing methods to actuate the soft structures. A popular method involves inflating soft hollow structures with a pneumatic pump that can achieve rapid and precise actuation. However, the structure must be tethered to a heavy and rigid pump, which limits its application. An alternative method vaporizes embedded liquid to inflate the structure instead. The simplest and widely used design to vaporize such liquid is by installing a heating element near the liquid. Heating the system beyond the boiling point rapidly boils the liquid and deforms the structure. The small amount of liquid and heater makes it easier to be packaged into a portable device. Nevertheless, this technique possesses several limitations that must be improved to be practical. This dissertation addresses these limitations and introduces methods that can advance the field for future robotics. Chapter 2 describes how actuation through vaporization can be affected by the environment and introduces a system that consists of double-layered walls and a thermoelectric device. Chapter 3 aims to implement ultrasonic waves that propagate through materials, which enables a system with detachable parts. Chapter 4 utilizes vibrating mesh atomization to drastically improve the slow actuation speed by evaporating small droplets with large surface areas. Last, chapter 5 introduces a method that can potentially remove electrical components by combining ultrasonics with shape optimization. These studies show that soft actuation through vaporization has significant room for improvement and can potentially replace commercial actuation methods with further optimization.

The overarching goal of this thesis relies in the exploration of design criteria, such as optimal material layout and geometry, to (1) create and (2) enhance the performance of innovative actuators and sensors, respectively. First, we present a bio-inspired multifunctional active skin, which is a two-dimensional architected material that exhibits local and/or global programmable, rapid, and reversible, out-of-plane surface texture morphing when actuated by in-plane tension. Here, by introducing geometrical imperfection or notches at judiciously chosen locations in a preconceived, auxetic geometry, we can effectively control the directionality of out-of-plane deformations for applications such as camouflage, surface morphing, and soft robotic grippers.

Second, an innovative “sensing mesh” capable of resolving both spatial strain magnitudes and directionalities for distributed strain field monitoring is introduced. The sensing mesh leverages the same concept of patterning to impart unique sensing capabilities in piezoresistive nanocomposites. In particular, the use of a grid-like layout with high aspect ratio struts resolves the strain sensing directionality limitations observed in previously reported sensing skins while also enhancing the sensitivity of the piezoresistive graphene-based thin films once coupled with an electrical impedance tomography conductivity mapping technique.

Finally, the design considerations explored in this thesis contribute to the development of an inverse design methodology of architected materials in which functionality parameters are first indicated and, then, optimal topologies for maximum effectiveness are indicated.