Mechanics and Fluidics at the Interface of Hard-Soft Materials


Arun Majumdar

Department of Mechanical Engineering, University of California, Berkeley, CA 94720

Materials Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA 94720


Hard and soft materials are characterized by the ratio of their respective binding energies (Eb) with respect to thermal fluctuations that are respresented by kT.  Mechanics and dynamics of hard materials (Eb >> kT) are generally unaffected by kT, except when undergoing irreversible processes such as transport phenomena or inelastic deformations.  On the other hand, fluctuations dominate the behavior of soft materials (Eb ~ kT) such as liquids and biomolecules, where entropic forces are critical in their mechanics.  As part of this lecture, I will focus on two topics, which relate to the interplay between entropic and non-dissipative forces:  (i) Transport of ions and biomolecules in nanofluidic structures and devices; and (ii) Actuation of mechanical devices such as cantilever beams and membranes using reactions of biomolecules (eg. DNA hybridization, antigen-antibody binding). I will also discuss the implications of our work on energy conversion and biomedical technologies.