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, visible light or high energy irradiation, and the presence of an electric or magnetic field. This, in combination with the unique optical properties of these emulsion droplets enables the application of complex emulsions as a new transduction material for chemo- and bio-sensing applications. Here, we will show examples of how the addition of stimuli-responsive surfactants to the complex emulsions provides a method to induce morphological changes or variations in the droplet alignment in response to the presence of specific chemical or biological analytes. In order to create an optical read-out, emissive dyes were added to one of the two immiscible phases of the complex emulsions. As a result, the unique chemical-morphological-optical coupling inside these complex emulsions led to the development of a series of new optical transduction methods. Specifically, the adjustment of the refractive indices of the two solvents resulted in a new unprecedented control of light propagation inside the emulsion droplets. Gaining control over the potential of these micro-colloids to manipulate light in form of waveguides paved the way towards the development of easily deployable liquid sensing platform that allow for the rapid and sensitive detection of various chemical and biological analytes, including a record-breaking detection scheme targeting the common foodborne pathogens Salmonella Typhimurium and E.coli.

Dynamic liquid colloids: A new sensing material for the rapid detection of food-borne pathogens

2019 Spring National Meeting

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