Brown University School of Engineering

Fluids Seminar: Biomimetic Devices from Soft Matter: Electrically Driven Colloidal Assemblies, Ionic Circuits and Hydrogel Actuators

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Tuesday, April 15, 2014 3:00pm - 4:00pm

Professor Orlin D. Velev Department of Chemical and Biomolecular Engineering North Carolina State University, Raleigh, NC 27695 odvelev@ncsu.edu; http://crystal.che.ncsu.edu/ Biomimetic Devices from Soft Matter: Electrically Driven Colloidal Assemblies, Ionic Circuits and Hydrogel Actuators We will present strategies for the fabrication of novel electrically functional structures from particles or gels operating in water environment. In the first part of the talk we will discuss how electric fields can be used to assemble metallic or dielectric particles into electrical connectors, networks and precursors of novel materials. The structures formed include microwires from metallic nanoparticles, crystals with conductive lanes, and biocomposites. We will focus on how Janus and patchy metallodielectric spheres and cubes can be assembled in unusual colloidal crystals and gels and how the type of structures formed can be precisely controlled by the induced frequency-dependent dipolar and quadrupolar interactions. A new class of permanently bound linear structures field-assembled from binary mixtures of microspheres of opposite charges with strongly attractive interactions will be reported. In the second part of the talk we will discuss how water-based gels doped with polyelectrolytes can be used as the core of novel diodes, memristors, photovoltaic cells and soft matter actuators. A class of “soft matter” diodes with rectifying junction was formed by interfacing hydrogels with oppositely charged counterions around their molecular backbones. We also demonstrated a radically new concept of bio-inspired hydrogel solar cells which are made of ionic agarose gels doped with photosensitive organic molecules. Finally, we will explain how hydrogels can be patterned and actuated by electrical or chemical means to form new types of actuators and soft robotic components.