Liquid Crystalline Elastomers

Photo-chromic liquid crystalline polymer (LCP) is a type of smart materials which are sensitive to light. Here we harness its photo-mechanical response to flexibly control surface patterning, through modeling a film involving homeotropic nematic liquid crystals with director perpendicular to the polymer film attached on a compliant substrate. Theoretical and numerical analyses were conducted to explore the surface instability of such film/substrate systems under both uniform and non-uniform illuminations by ultraviolet (UV) light, respectively.

Given a distribution of defects on a structured surface, such as those represented by 2-dimensional crystalline materials, liquid crystalline surfaces, and thin sandwiched shells, what is the resulting stress field and the deformed shape? Motivated by this concern, we first classify, and quantify, the translational, rotational, and metrical defects allowable over a broad class of structured surfaces. With an appropriate notion of strain, the defect densities are then shown to appear as sources of strain incompatibility.

Dear iMechanica,

Last July I posted a journal club entry on overcoming the traditional challenges in mechanically actuating liquid-crystalline elastomers (http://imechanica.org/node/16853). I'm glad to say we finally got our first manuscript regarding this work published in RSC Advances (DOI: 10.1039/C5RA01039J). 

Smart materials are designed to have a controlled response to external stimuli. Shape-memory polymers (SMPs) are one of the most well known classes of mechanically active smart materials and have experienced an incredible amount of research attention over the last decade. They are able to recover programmed deformations when heated above a thermal transition; however, are generally considered a one-time event. Liquid-crystalline elastomers (LCEs) are another class of actively moving polymers; however, these materials can demonstrate reversible and repeatable shape memory without the need for “re-programming” after each actuation cycle.