multi-filed actuation of polymer based structures
Open Access
- Author:
- Masters, Sarah Renee
- Area of Honors:
- Interdisciplinary in Engineering Science and Mechanical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Zoubeida Ounaies, Thesis Supervisor
Clifford Jesse Lissenden III, Thesis Honors Advisor
Mary I Frecker, Faculty Reader - Keywords:
- Active Material
Origami
Multi-field
Terpolymer
MAE
Engineering Science
Bending
Folding - Abstract:
- In this project, active materials and sample configurations were explored with the goal of creating multi-field actuators, i.e., materials that respond to multiple stimuli to deform and change shape. Specifically, PVDF-TrFE- CTFE (terpolymer) and PDMS with barium ferrite particles were the two types of active materials used. Terpolymer is an electroactive polymer material, which actuates when an electric field is applied, and the PDMS with barium ferrite particles is a magnetoactive material, which actuates when placed in a magnetic field. By building different actuator configurations using these active materials, deformation and shape change can be achieved using both electric and magnetic fields. The main two motions observed throughout this project were bending (curvature across the entire sample) and folding (localized curvature at a notch). First, bending in a unimorph was explored; the unimorph was fabricated using solution cast terpolymer as the active material with scotch tape added to the sample as the inactive material. When an electric field is applied to this type of sample, the nanodomains present in the terpolymer cause it to contract in the thickness and expand in the length of the sample. Attaching a layer of scotch tape (inactive substrate) to the terpolymer restricts the planar expansion of the terpolymer when electric field is applied. This configuration, referred to as a unimorph, results in a bending motion towards the inactive substrate under electric field. Next, notches are introduced in the unimorph to transform the bending into folding; specifically, two smaller pieces of scotch tape were added on to the single layer of tape that was first placed on the terpolymer. A gap, i.e., notch, is left in between the two smaller pieces of tape that are added to the top of the sample. In the notched area, since there is less inactive substrate, these areas will exhibit more localized bending than the rest of the samples. Both single notch and double notch folding were explored. Double notch samples showed greater actuation, to the point where the sample curled up on itself because a large amount of folding was produced in both notches. Next, PDMS with barium ferrite particles was used to create a unimorph bender that would actuate when a magnetic field was applied. The barium ferrite particles are permanent magnetic particles, so when they are added to the PDMS and the entire sample is cured under a magnetic field, the resulting material has a magnetic pole direction. When the sample is then placed in an applied magnetic field, the sample actuates (bends) to try to align the poled direction of the sample with the direction of the external magnetic field. Finally, terpolymer and PDMS with barium ferrite particles were combined (attached together using an adhesive spray) into a bimorph structure. Both bending and folding actuators were investigated using this bimorph configuration. These multi-field actuators respond to both electric and magnetic fields. In conclusion, multi-field actuation of a single bimorph sample was achieved using both an electric and magnetic field. Both multi-field bending and folding were successfully demonstrated and quantified.