2 research outputs found
Autonomic Molecular Transport by Polymer Films Containing Programmed Chemical Potential Gradients
Materials which induce
molecular motion without external input
offer unique opportunities for spatial manipulation of molecules.
Here, we present the use of polyacrylamide hydrogel films containing
built-in chemical gradients (enthalpic gradients) to direct molecular
transport. Using a cationic tertiary amine gradient, anionic molecules
were directionally transported up to several millimeters. A 40-fold
concentration of anionic molecules dosed in aerosol form on a substrate
to a small region at the center of a radially symmetric cationic gradient
was observed. The separation of mixtures of charged dye molecules
was demonstrated using a boronic acid-to-cationic gradient where one
molecule was attracted to the boronic acid end of the gradient, and
the other to the cationic end of the gradient. Theoretical and computational
analysis provides a quantitative description of such anisotropic molecular
transport, and reveals that the gradient-imposed drift velocity is
in the range of hundreds of nanometers per second, comparable to the
transport velocities of biomolecular motors. This general concept
of enthalpy gradient-directed molecular transport should enable the
autonomous processing of a diversity of chemical species
Chemical Gradients on Graphene To Drive Droplet Motion
This work demonstrates the production of a well-controlled, chemical gradient on the surface of graphene. By inducing a gradient of oxygen functional groups, drops of water and dimethyl-methylphosphonate (a nerve agent simulant) are “pulled” in the direction of increasing oxygen content, while fluorine gradients “push” the droplet motion in the direction of decreasing fluorine content. The direction of motion is broadly attributed to increasing/decreasing hydrophilicity, which is correlated to high/low adhesion and binding energy. Such tunability in surface chemistry provides additional capabilities in device design for applications ranging from microfluidics to chemical sensing