Published: Nov. 18, 2021 By

Liquid crystal elastomers undergoing directional actuation and deformation in response to electrical fields

Hayden Fowler, a graduate student in Gallogly Professor Timothy White’s Responsive and Programmable Materials Group, is the first author on a research paper published in Advanced Materials concerning the temperature-independent electrical actuation of liquid crystal elastomers (LCEs), which are soft, stimuli-responsive materials with potential applications in soft robotics, artificial muscles and more.

These LCEs are crosslinked polymer networks of rod-like units whose orientation enables the control of their formations, including directional actuation and 3-D deformations. Heat and light have traditionally been used as stimuli to control LCEs in laboratory environments, but are not viable in independent devices due to poor efficiency and responsiveness.

Fowler took inspiration from nature in tackling this research challenge.

“Many naturally occurring systems can efficiently and effectively convert input energy into mechanical response,” Fowler said. “For example, the human hand integrates sensing, structure and actuation to accomplish high force as well as gentle dexterity. However, it is an ongoing challenge to incorporate all these capabilities into man-made or robotic systems.”

Fowler, White and their partners sought to apply a controlled electric field to manipulate the LCEs. They applied electrodes to opposite sides of an LCE formation. Because LCEs can be aligned and directed, they expanded in “softer” directions with response times much faster than traditional heat and light methods.

“I have really enjoyed working with Hayden thus far on their research,” said White. “They did a great job to drive this difficult project to completion. Hayden worked closely with Dr. Philipp Rothemund of the Keplinger group to quickly come up a learning curve in this new area of research for my group. I’m excited to see where Hayden takes their research as they finalize their PhD.”

Professor Christoph Keplinger and his postdoctoral associate Philipp Rothemund of the Max Planck Institute for Intelligent Systems in Stuttgart, Germany provided essential contributions to the research.

“Keplinger and Rothemund were instrumental in bringing me up the learning curve on this project, and Rothemund contributed his knowledge of modeling these types of actuators to theoretically predict their performance based purely on the physical, measurable properties of the materials,” Fowler said.

White is an expert in synthesis and alignment of LCE materials, Fowler said, noting his knowledge gained at the Air Force Research Lab helped push the project forward. They credited White’s group and the Department of Chemical and Biological Engineering as possessing unique strengths in processing and characterizing the materials used in the research. White’s group was also prepared to test and evaluate performance in materials actuator applications.

“One of my goals is to improve the materials chemistry, and therefore the performance, of these actuators,” Fowler said. “I am interested in probing the effects of network structure, processing, phase behavior and monomer content on the properties of the material that affect their performance as electromechanical actuators. These include but are not limited to the material’s recoverability, dielectric properties and stiffness.”