• Starts: 3:00 pm on Friday, April 19, 2024
  • Ends: 4:00 pm on Friday, April 19, 2024
Speaker: Dr. Thomas Russell, UMass Amherst

Title: Self-Propulsion by Directed Explosive Emulsification

Abstract: We will present an active droplet system, programmed to repeatedly move autonomously at a specific velocity in a well-defined direction, is demonstrated. Coulombic energy is stored in oversaturated interfacial assemblies of charged nanoparticle–surfactants by an applied DC electric field and can be released on demand. Spontaneous emulsification is suppressed by an increase in the stiffness of the oversaturated assemblies. We quantified the packing of the assembly as it is driven into the oversaturated state under an applied electric field. Rapidly removing the field releases the stored energy in an explosive event that propels the droplet, where thousands of charged microdroplets are ballistically ejected from the surface of the parent droplet. The ejection is made directional by a symmetry breaking of the interfacial assembly, and the combined interaction force of the microdroplet plume on one side of the droplet propels the droplet distances tens of times its size, making the droplet active. The propulsion is autonomous, repeatable, and agnostic to the chemical composition of the nanoparticles. The symmetry-breaking in the nanoparticle assembly controls the microdroplet velocity and direction of propulsion. This mechanism of droplet propulsion will advance soft micro-robotics, establishes a new type of active matter, and introduces new vehicles for compartmentalized delivery.

Bio: Thomas P. Russell, the Silvio O. Conte Distinguished Professor of Polymer Science and Engineering at the University of Massachusetts in Amherst, received his PhD in 1979 in Polymer Science and Engineering from the University of Massachusetts Amherst, a Research Associate at the University of Mainz (1979-1981), a Research Staff Member at the IBM Almaden Research Center in San Jose, CA (1981-96). He is also a Visiting Faculty at the Materials Science Division in the Lawrence Berkeley National Laboratory, and a PI at the Advanced Institute of Materials Research at Tohoku University He has over 1,000 publications, 40 patents, edited 5 books, and has an H-index of 167. He is a Fellow of the American Physical Society, Materials Research Society, Neutron Scattering Society of America, American Association for the Advancement of Science, and the American Chemical Society, Polymer Materials Science and Engineering Division. He has received the Polymer Physic Prize of the APS, the Cooperative Research Award of the ACS, the Dutch Polymer Award, the ACS Award in Applied Polymer Science, Society of Polymer Science Japan International Award, Shull Prize of the Neutron Scattering Society of America and is an elected member of the National Academy of Engineering and the National Academy of Inventors.

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