ELECTROACTIVE POLYMER-BASED MATERIALS FOR RESPONSIVE ORIGAMI-INSPIRED STRUCTURES

With the ever-growing usage of technology in our day-to-day life, the demands on existing energy sources, sustainable technology, and space requirements are also increasing. As a result, increasing interests are focused on technologies with benefits such as reduced space requirements, reduced material consumption, and improved energy efficiency. Origami-inspired engineering has gained much attention among scientists, engineers and mathematicians as an emerging form of technology with potential advantages such as relatively simple assembly process, realization of a large number of structures/shapes from a single sheet and finally, capability of folding into a compact shape and then unfolding (deploy or launch) into a larger complex shape. Self-folding mechanism coupled with origami-inspired engineering is of particular interest where the structure has the ability to fold and unfold in response to an external stimulus without manual assistance. Researchers have investigated several self-folding mechanisms to realize origami-inspired engineering. In this work, an electroactive polymer (EAP), more specifically poly (vinylidende fluoride-trifluoroehtylene-chlorotrifluoroethylene) P(VDF-TrFE-CTFE), is studied and implemented to achieve origami-inspired self-folding structures. P(VDF-TrFE-CTFE) is used to realize electric field driven origami-inspired smart structures because of high room temperature dielectric constant (~50), fast response and reversible actuation mechanism. Processing condition of P(VDF-TrFE-CTFE) is studied based on the microstructure and electromechanical properties. Then a detail electrical, electromechanical, analytical, thermal, mechanical characterization on P(VDF-TrFE-CTFE) is performed and presented. Through dielectric spectroscopy it is observed that the Curie transition of terpolymer shows a broad peak unlike normal ferroelectric polymer. Polarization study reveals very slim (less lossy) hysteresis loop. The current understanding of the origin of electrostrictive strain is attributed to phase transition from paraelectric to ferroelectric phases. In this work, electric field in-situ X-ray diffraction (XRD) and sum frequency generation (SFG) study are conducted to investigate and confirm the switching of α and γ phases to polar -phase. To enable electric field-driven on-demand bending and folding of P(VDF-TrFE-CTFE), various approaches are undertaken. First, electric field-driven large bending is achieved using a one layered unimorph actuator. Two approaches are pursued to convert the bending actuation into folding: notches and stiffener. While stiffener approach was not very successful, the notch approach showed more pronounced folding actuation. However, EAP actuators also possess drawbacks that impede their implementation in applications, namely they induce relatively low force and require high actuation voltages. To address these issues, a multilayered unimorph concept is proposed. Due to the complex fabrication process of multilayered unimorph actuator and the large number of experimental parameters, a universal analytical model is developed in this work to guide the experimental design and fabrication of these actuators. The model is based on a set of non-dimensional equations for electric field-induced curvature, tip displacement and blocked force, taking into account the wide range of design parameters (such as thickness, modulus, number of layers, electric field magnitude, etc.). First, analytical results are validated