Biological organisms can adapt with respect to their environments by exploiting a wide range of pre-determined and self-regulated motions. These reconfigurations allow organisms to dynamically tune material properties such as adhesion, wettability, and coloration. In contrast, artificial materials often lack the adaptive responses observed in natural systems and are limited by their reliance on multi-material designs. This restricts the range of their deformation behaviors and functionalities. An adaptive material with molecular scale programmability would provide opportunities for the rational design of next generation responsive materials, and potentially transform areas ranging from artificial muscles to self-cleaning surfaces and homeostatic systems.

Liquid crystal elastomers (LCE) are a promising materials to achieve the desired programmability and deformation capabilities. LCEs consist of anisotropic molecules known as mesogens covalently bound to a polymeric background material (the elastomer). On their own, mesogens behave as liquid crystals (LC), i.e. they can be aligned into a variety of LC phases such as nematic, smectic, and chiral nematic. As the mesogen alignment is coupled to the extension of the elastomer, molecular scale reconfigurations will lead to macroscopic changes.

A variety of approaches have been developed to prescribe the alignment of the mesogens. In the Aizenberg group, we typically employ magnetic fields to impose the liquid crystal director. This method can be applied to and programmed within any 3D shape, thereby allowing us to encode macroscopic deformation modes at the molecular level, which can then be read out upon application of external stimuli. The molecular-to-macroscopic coupling can be designed at the molecular level through the choice of mesogen and elastomer at the molecular level, as well as other aspects such as crosslinking density, characteristics of the stimulus, etc. This ‘plug-and-play’ opportunity makes LCE-based materials a versatile platform to create biomimetic structures with a palette of responses and functions.

In the Aizenberg group, we have used magnetically aligned LCEs to create a variety of multiresponsive microstructures such as microposts, microplates, interconnected cellular structures, and closely spaced arrays. We are interested in furthering our fundamental understanding of self-regulated systems, as well as expanding these designs into applications such as autonomous multimodal actuators in switchable adhesives, information encryption, autonomous antennae, energy harvesting systems, soft robots, and smart buildings.

This research is highly interdisciplinary and brings together a team of synthetic chemists, physicists,  and mechanical engineers, both theorists and experimentalists. Experimental techniques include organic synthesis, confocal microscopy, and regular trips to the synchroton at Brookhaven National Labs to perform x-ray scattering experiments to gain insight into the molecular organization under various conditions. Theoretical/comutational approaches include analytical theory and finite element simulations.