Squishy Physics

Next seminar: Wednesday March 21st in Pierce 209 at 5:30 PM:


Rapid Detection of Foodborne Pathogens using Directional Emission from Dynamic Complex Emulsions


Lukas Zeininger

Departament of Chemistry

Massachusetts Institute of Technology



Multiphase complex emulsions formed from two or more immiscible solvents offer a unique platform as new materials for chemical sensor applications. The temperature controlled miscibility of fluorocarbons (F) and hydrocarbons (H) enables a temperature induced phase-separation, leading to structured emulsion droplets of H and F in water (W), which can be alternated between encapsulated (F in H, and H in F), and Janus configurations by varying the interfacial tensions using surfactants. These complex emulsion droplets can selectively invert morphology in response to external stimuli such as the presence of specific analytes, small pH changes, light or high energy irradiation, and the presence of an electric or magnetic field. This, in combination with the unique optical properties of our emulsion droplets enables the application of our complex emulsions as a new transduction material for chemo- and bio-sensing applications. Here, we will show how the addition of stimuli-responsive surfactants to the complex emulsions provides a method to induce a morphology change or droplet reconfiguration as a response to the presence of specific chemical or biological analytes. In order to create a ratiometric optical read-out of small changes in the droplet morphology, emissive dyes were added to one of the two immiscible phases of the complex emulsions. The potential of these micro-colloids to manipulate light in form of waveguides led to the development of several optical transduction methods, where an adjustment of the refractive indices of the solvents results in a new unprecedented control of light propagation inside the emulsion droplets. We will demonstrate that having control over the total internal reflection of light from outside and inside the emulsion droplets results in new sensory schemes for the rapid and sensitive detection of various chemical and biological analytes, including common foodborne pathogens such as Salmonella and E.coli bacteria.  


Squishy Physics & Pizza Seminar Series

When: Wednesday Evenings - Pizza served at 5:20 PM, talks start at 5:30pm till...

Where: Room 301, Pierce Hall, 29 Oxford St, on the Harvard Campus. Directions and parking instructions are here.

What: These talks are informal, with emphasis on new results and ideas, rather than polished presentations. The Squishy audience members typically include soft matter scientists, physicists, engineers, chemists, and biologists.  The goal is to stimulate discussion with the audience.  Talks are typically about 45 minutes long, with lots of questions along the way.

Pizza: Only the finest! 

How to join the weekly Squishy Physics mailing list: please visit the Signup Page.

Directions: Where: Squishy Physics talks are held in Pierce Hall room 301, 29 Oxford Street, Cambridge, MA. See Harvard Campus map here.

Parking: Metered parking is available on Oxford Street.  Speakers, please contact Matthew Zahnzinger to obtain a parking permit.  

Squishy Physics is sponsored by the Cabot Corporation, Dean Cherry Murray and the Weitz Research Group.

If you have comments or suggestions or would like to give a talk, please contact Joerg Werner or Raoul Rosenthal.

Here is the upcoming schedule