Development and characterization of active terpolymer for origami-inspired actuation

Open Access
Author:
Arrojado, Erika
Area of Honors:
Mechanical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Zoubeida Ounaies, Thesis Supervisor
  • Zoubeida Ounaies, Honors Advisor
  • Mary I Frecker, Faculty Reader
Keywords:
  • origami engineering
  • PVDF terpolymer
  • active materials
Abstract:
Origami engineering is a new field in which researchers are seeking to apply the art of paper folding to advantageous engineering applications. One of these applications is in the biomedical field where an origami stent can fold compactly for insertion into the body and expand when needed due to a small electrical or magnetic field. Similarly, another application is in solar satellites that are folded into smaller packaging to be easily launched into space and then expanded for larger functionality. Our research group is investigating use of active materials to actuate origami-inspired structures such as these, in response to different external fields. This specific study involves the active material known as P(VDF-TrFE-CTFE), a PVDF-based relaxor ferroelectric terpolymer. The terpolymer responds to electric field; when a field is present, the random dipoles in the film align with the field, causing the film to contract in thickness and expand in-plane. The films are electroded then adhered to a substrate in a configuration called unimorph. Upon application of the electric field, the substrate restricts the expanding motion of the terpolymer, resulting in an overall bending motion of the system. This bending motion is exploited to actuate the so-called origami in action structures. In order to understand the behavior, capabilities, and limitations of the terpolymer as an active material, both qualitative and quantitative data are collected from the actuation of three different action origami structures: the flapping butterfly, the catapult, and the barking dog. The goal is to find the optimal shapes and crease patterns of the structures as well as the optimal configurations with the terpolymer film. These three structures are tested and the research has shown that PVDF-terpolymer is an effective actuator with ability to deform a substrate to a desired shape in the presence of an electric field. The butterfly was able to flap, the mouth of the dog was able to “bark,” and the catapult was able to launch a small ball of paper. Through experimentation, it was determined what parameters affect actuation and furthermore what values of those parameters will maximize the actuation. These trends can then be used to predict further improvement in the resulting mechanical output of the action origami structures.