Composites for Electromagnetically Active, Soft Materials to Improve Quality of Life

Composite materials are an attempt to make something that is better than the sum of its parts.  Polymer composites in particular take advantage of the rheological or mechanical properties of the polymer while adding new properties not available from polymers such as electromagnetism.  The Koh Lab focuses on understanding and taking advantage of the functionality that comes from blending electromagnetically active fillers with liquid or solid polymers.  For example, in the field of soft robotics and stretchable electronics there is a great need for materials that can conform to the human body, are lightweight with low power requirements, are resistant to mechanical shock, and are highly sensitive to the environment all without sacrificing basic electrical properties like conductivity or permittivity.  To address these needs, the Koh Lab creates composites of elastomers and room temperature liquid metals, specifically galinstan, which is an alloy of gallium with a melting point below 0oC.  We investigate the fundamental interplay between the mechanical and electrical properties of these liquid metal polymer composites (LMPCs) to determine how we can create materials with low compressive, tensile, and torsional modulus in addition to high dielectric permittivity, low dielectric loss, and high dielectric breakdown strength.   In addition to our fundamental investigation of LMPCs, the Koh Lab works on integrating LMPCs into devices such as sensors for physiological measurements (e.g., breathing, gait patterns) and robotics (e.g., actuators).  A second area of composites that the Koh Lab focuses on is a blend of magnetic particles and non-conductive fluid, called magnetorheological fluids (MRFs).  MRFs reversibly transition between a low-viscosity state and high-viscosity state when a magnetic field is applied.  The change in viscosity, and a concomitant increase in yield stress, is due to the formation of particle chains in the direction of the magnetic field.  MRFs can be used for energy dissipation in earthquake dampers and prosthetics/orthotics, but challenges remain before MRFs can be used commercially.  The Koh Lab focuses on the power requirement for MRFs, as the magnetic field is typically generated through an inductor and a stronger field, which leads to stronger chains, requires more current.  To create MRFs that can achieve higher performance with lower power we have investigated a wide variety of MRF formulations and the impact of fluid additives.  Additionally, we have developed a new magnetoflow-microscope that enables us to visualize chain formation and flow patterns to deeply understand why we are seeing the rheological changes measured.  Altogether, the Koh Lab focuses on developing new composite materials from the ground up and using our expertise in fundamental characterization and device integration for improved quality of life, national infrastructure, and personal healthcare.

Additional Information:

Dr. Amanda Koh is an Assistant Professor at the University of Alabama in the Department of Chemical and Biological Engineering.  She joined UA in 2018 after completing her postdoctoral fellowship at the Army Research Laboratory in Aberdeen Proving Ground, MD.  Dr. Koh received her Ph.D. in Chemical Engineering from Rensselaer Polytechnic Institute in Troy, NY and her B.S. in Chemical Engineering from the Massachusetts Institute of Technology in Cambridge, MA.