EAGER: Direct Ink Writing of Molecularly Patterned Polyionic Actuators

University Of Pittsburgh, Pittsburgh PA

Investigators

Abstract

This EArly-concept Grant for Exploratory Research (EAGER) award supports research which will demonstrate 3D printing of polymeric materials that transport charges through their bulk, while simultaneously functioning as artificial muscles, which convert thermal energy into mechanical work. A key breakthrough envisioned by this research is the ability to align ionic species within a polymer network, where their organization can be dictated during the printing process but remain susceptible to reconfiguration using stimuli thereafter. Accomplishing this can enable the manufacturing of multifunctional components that could impact an array of technological sectors. Printable materials with mutable mechanical, electronic, and ionic properties may enable novel designs of structures like a) tunable electrolytes for freeform batteries, b) sensory materials for soft robots that can self-report their actuation state, and c) responsive biomaterials that can actively modulate their interaction with microbial/biological agents. To achieve this goal, fundamental questions on how process parameters affect the configuration of charged species within a polymer network remain to be answered. This research will address these issues using material synthesis, optimization of manufacturing processes, characterization techniques, and mechanical design. This research will explore the structure-property-performance mappings that underpin reversible actuation in 3D-printed, ionic liquid crystalline elastomers (LCE). The effect of extrusion parameters applied during direct ink writing (DIW) of LCE composed of mesogenic acrylates and ionic chain extenders will be examined. Efforts will focus on measuring the influence of the shear stresses imposed during the printing process on the homogeneity of the molecular alignment, characterizing the role of the molecular structure on the resulting properties, and harnessing these characterizations in freeform artificial muscles that respond to stimuli. The effect of the ionic groups in the backbone of the LCE on the stability of the molecularly ordered state will be explored as a function of the composition, molecular structure, and the processing history. Ionic monomers compatible with canonical liquid crystalline monomers will be synthesized to create 3D printable inks. The composition of the inks and the DIW printing parameters will be studied to measure the endowment of the liquid crystalline order, phase stability and structure. The resulting samples will be characterized for their actuation in response to stimuli, their ability to sense deformation/strain, and their integration into freeform soft robotic architectures. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.