Chemical Reaction Evolving on a Droplet

Abstract

A high-speed camera was used to investigate the early stage of a chemical reaction within a few milliseconds. We focus on the process of color change caused by a droplet containing a pH indicator when impinging on the surface of alkaline solution. Contrary to our expectation, this reaction starts along the equatorial line, and not at the protruding edge of the droplet, where it first touches the reaction partner. Small vertical fingers emerge from the front line within 1.5 ms. The results suggest that the observed deformation of the droplet and heat diffusion play major roles during this early reaction stage. Our investigations contribute to the understanding of short-term transport processes across interfaces, including the onset of unstable behavior of reaction fronts.

Asymmetric Rayleigh-Taylor and double-diffusive fingers in reactive systems

“…[16][17][18] and references therein) and combustion problems. 12,19 In parallel, the coupling between convective motions and a simple A + B → C reaction has been addressed both experimentally [20][21][22][23][24][25][26][27][28][29] and theoretically. 24,27,[29][30][31][32] In the specific a) L. Lemaigre and M. A. Budroni contributed equally to this work.…”

Chemical reaction and mixing inside a coalesced droplet after a head-on collision

“…These phenomena of inhomogeneity generally occur over a few seconds or even a few minutes. The evolution of a chemical reaction inside a droplet was investigated on letting a drop containing pH indicator bromothymol blue fall into an alkaline liquid; the results indicated that the observed deformation of the droplet and the diffusion of heat play major roles during this early reaction stage (Tsuji and Muller 2012). Koh et al (2013) investigated the platform that allows a ferrofluid droplet to be driven along a preprogrammed path; the chemical reaction (acid/base titration with a pH indicator) inside the droplet was demonstrated on this platform.…”

Magnetically-Actuated Mixing and Merging of Acid-Base Micro-Droplets on Open Surfaces: Preliminary Study

“…Several groups already reported on the hydrodynamics, kinematics and chemical reactions of the reactive micro-droplets. Tsuji and Muller [ 21 ] studied the early stage of the chemical reaction when a droplet of bromothymol blue (16 μL) was laterally impinged on the surface of 0.1 M sodium hydroxide (NaOH) solution. The merging process was recorded using a high speed camera.…”