Visualization of Chemical Phenomena

Droplets having a diameter in the micrometer range can have unique and interesting properties, which arise because of their small size and, especially, their high surface area-to-volume ratio. Students are generally unfamiliar with the characteristics of small droplets. However, with the increasing importance of miniaturization in chemistry and biochemistry, especially in the burgeoning field of microdroplet microfluidics, it would be beneficial for students to become aware of some of the features that differentiate chemistry on a small scale. To better acquaint students with these features, we have developed microdroplet systems that model microfluidics in a "stop-action" manner. Using a micropipet manipulation technique combined with video microscopy, chemical reactions and physical phenomena that occur in one or more individual water droplets surrounded by an immiscible liquid are visualized. The outcomes of various types of physical and chemical phenomena, including redox reactions, precipitation reaction, interfacial extraction of metals, solubility of water in oils, and crystallization can be readily illustrated. Each system is understood as a dramatic exploitation of the small size of microdroplets having a large surface area-to-volume ratio.

For more details, please visit our recent publication. (undergraduate co-authors are underlined)

S.Lee, J.Wiener, "Visualizing Chemical Phenomena in Microdroplets", J. Chem. Educ., 88 (2), 151-157, 2011. (Featured as Cover Art, Feb. 2011 Issue of J. Chem. Educ.) http://pubs.acs.org/doi/abs/10.1021/ed100518k

Link to Cover Art: http://pubs.acs.org/action/showLargeCover?issue=356109856

QuickTime Player is needed to play the videos below:

  1. Water Droplet Dissolution into Octanol
  2. Water Droplet Dissolution into Decanol
  3. Water Droplet Dissolution into Dodecanol
  4. Crystallization of K2CrO4
  5. Crystallization of K4Fe(CN)6 Trihydrate
  6. Complexation Reaction: NH3 (aq) with CoCl2 (aq)
  7. Complexation Reaction: NH3 (aq) with CuSO4 (aq)
  8. Complexation Reaction: NH3 (aq) with Pb(NO3)2 (aq)
  9. Redox Reaction: K2CrO4 with Ascorbic Acid