Soft matter, Fluidics and Interfaces

Transport phenomena in Catalytic micropump

Introduction

The autonomous motion for catalytic nanorods within an aqueous medium has been reported in literature [1][2]. A single nanorod consists of a bimetallic couple that catalyzes the decomposition of an aqueous solution such as hydrogen peroxide, thereby creating the necessary gradients (electric, concentration) that actuate motion. Immobilization of this system will generate an interfacial convective flow, that can be studied in situ to obtain fundamental insights in electro-diffusio osmotic mechanism serving as the driving force.

Working principle

The catalytic micropump consists of platinum/gold bi-metallic couple, and when immersed in hydrogen peroxide solutions, triggers a series of oxidation and reduction reactions (Eqns 1-3), where  is oxidized at the platinum anode into protons, electrons, and oxygen molecules, while reduction takes place at the gold cathode. The resulting ionic flux generates an electric field that is coupled with the charge density, thereby inducing an electric body force that drives interfacial fluid motion 

Tasks

  • The Bipolar electrochemical mechanism will be studied using electrochemical techniques e.g Potentiometry and Amperometry techniques , impedance spectroscopy e.t.c.
  • Concentration gradients and proton distributions will be mapped using Fluorescence lifetime imaging microscopy (FLIM) and TIRF.
  • The flow profiles generated by the asymmetric surface reactions, will be studied using, OCT and microPIV and
  • Existing numerical models will be improved on and validated with experimental results using interesting scaling relation between the velocity, potential and Damköhler numbers [3].

 

References

[1]         Kline, T. R., Paxton, W. F., Mallouk, T. E., & Sen, A. (2005). Catalytic Nanomotors: Remote-Controlled Autonomous Movement of Striped Metallic Nanorods. Angewandte Chemie International Edition, 44(5), 744–746.

[2]         Y. Wang et al., “Bipolar electrochemical mechanism for the propulsion of catalytic nanomotors in hydrogen peroxide solutions,” Langmuir, vol. 22, no. 25, pp. 10451–10456, 2006.

[3]         S. M. Davidson, R. G. H. Lammertink, and A. Mani, “A Predictive Model for Convective Flows Induced by Surface Reactivity Contrast”, submitted, 2017. (https://arxiv.org/abs/1704.07420)