AFRL shape-changing materials make form a function

  • Published
  • By Holly Jordan
  • AFRL Materials and Manufacturing Directorate
WRIGHT-PATTERSON AIR FORCE BASE --  AFRL research is shaping the future of aerospace. 

Through research into soft materials called liquid crystal elastomers, AFRL scientists have developed a method to locally program the mechanical response in polymer sheets without the use of actuators and traditional mechanical parts.  This research (sponsored by the Air Force Office of Scientific Research) is another step toward a "smart" material that enables a structural element to change shape and, therefore, functionality.  The local control of the mechanical response is referred to as "voxels" (short for "volume elements"), comparable to the pixelated liquid crystalline displays used in television, cell phones, and computer monitors. 

Because these voxelated liquid crystal elastomers are sensitive to temperature, the material can be programmed to respond to heat.  When heat is applied, the material changes at the molecular level, which forces a macroscopic structural change.  This result can be demonstrated as a transformation of a flat film to a 3-D structure, including self-folding origami.  When the heat stimulus is removed, the process is reversed.

Dr. Taylor Ware, a post-doctoral researcher at AFRL, compares these materials to rubber bands, but says "they are programmed to autonomously change shape and do useful work."  He says the materials can be actuated under loads up to four hundred times greater than their own weight.

Dr. Timothy White, the AFRL research lead and principal investigator on the effort, says the exploration of these materials is not new.  In fact, researchers have been looking into these technologies for over 50 years.  However, he says that the AFRL discoveries were inspired by and build upon this prior research and could be easily scaled up to quantities relevant to aerospace applications.

Although the basic research of these materials is still in the early stages, Dr. White says potential uses are being explored, including structurally integrated antennas, jointless morphing aircraft skins, flexible wing structures, and collapsible solar cells.  Commercial and medical uses could also be on the horizon.

The AFRL researchers are quick to point out, however, that more work is needed before the potential of the material's programmability is fully assessed.  Future research efforts will focus on improving the material response to heat actuation as well as examination of other stimuli such as light to remotely trigger the shape-changing response.  This research is a part of a larger effort focused on the materials and mechanics of shape-changing systems ongoing within the Materials and Manufacturing and Aerospace Systems Directorates of AFRL. 

The AFRL team's research is featured in the February 27, 2015, edition of the journal Science.