Mechanical and Civil Engineering Seminar

Mechanical and Civil Engineering Seminar Series

Title: Enabling Functional Outcomes by Programming the Responsivity of Liquid Crystalline Polymer Networks and Elastomers

Abstract: Liquid crystalline materials are pervasive in our homes, purses, and pockets. It has been long-known that liquid crystallinity in polymers enables exceptional characteristics in high performance applications such as transparent armor or bulletproof vests. This talk will generally focus on a class of liquid crystalline materials referred to as liquid crystalline elastomers. These materials were predicted by de Gennes to have exceptional promise as artificial muscles, owing to the unique assimilation of anisotropy and elasticity. Subsequent experimental studies have confirmed the salient features of these materials, with respect to other forms of stimuli-responsive soft matter, are large stroke actuation up to 75% as well "soft elasticity" (stretch at minimal stress).

This seminar will survey our efforts in directing the self-assembly of these materials to realize distinctive functional behavior with implications to soft robotics, flexible electronics, and biology. Most notably, enabled by the chemistries and processing methods developed in my laboratories, we have prepared liquid crystal elastomers with distinctive actuation and mechanical properties realizing more than 100 J/kg work capacities in homogenous material compositions. Local control of orientation dictates nonuniformity in the elastic properties, which we recently have shown could be a powerful means of ruggedizing flexible electronic devices. Fibers and yarns are promising geometries to further enhance the exceptional stimuli-response of these materials.

Bio: Timothy J. White is the Gallogly Professor of Engineering at the University of Colorado Boulder. Tim received his Ph.D. in Chemical and Biochemical Engineering in 2006 from the University of Iowa and subsequently joined the Air Force Research Laboratory where he served as a Senior Research Engineer and Technology Advisor of the Photonic Materials Branch. In 2018, Tim joined the faculty at the University of Colorado Boulder. Tim leads the "Responsive and Programmable Materials" Group (https://www.colorado.edu/research/rpmgroup/), pursuing research generally focused on programming functional responses in organized materials. Prof. White has more than 150 papers in peer-reviewed journals. Dr. White has been honored with the 2019 Soft Matter Lectureship, 2016 Materials Research Society "Outstanding Young Investigator" award, the 2013 SPIE Early Career Achievement award, the 2013 American Chemical Society PMSE Division Award for "Cooperative Research in Applied Polymer Science", and the 2012 Air Force Early Career Award.

NOTE: At this time, in-person Mechanical and Civil Engineering Lectures are open to all Caltech students/staff/faculty/visitors.