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Dynamic Gradient Directed Molecular Transport and Concentration in Hydrogel Films
Author(s) -
Tsai TsungHan,
Ali Mohammad A.,
Jiang Zhelong,
Braun Paul V.
Publication year - 2017
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201700166
Subject(s) - concentration gradient , ionic bonding , traveling wave , diffusion , dissipative system , molecule , chemical physics , ion , chemical engineering , materials science , molecular dynamics , ammonium , chemistry , nanotechnology , polymer chemistry , organic chemistry , computational chemistry , thermodynamics , physics , mathematical analysis , mathematics , engineering
Abstract Materials which selectively transport molecules along defined paths offer new opportunities for concentrating, processing and sensing chemical and biological agents. Here, we present the use of traveling ionic waves to drive molecular transport and concentration of hydrophilic molecules entrained within a hydrogel. The traveling ionic wave is triggered by the spatially localized introduction of ions, which through a dissipative ion exchange process, converts quaternary ammonium groups in the hydrogel from hydrophilic to hydrophobic. Through a reaction–diffusion process, the hydrophobic region expands with a sharp transition at the leading edge; it is this sharp gradient in hydrophilicity that drives the transport of hydrophilic molecules dispersed within the film. The traveling wave moved up to 450 μm within 30 min, while the gradient length remained 20 μm over this time. As an example of the potential of molecular concentration using this approach, a 70‐fold concentration of a hydrophilic dye was demonstrated.