Photo-control of nanointeractions.

The manipulation of physical interactions between structural moieties on the molecular scale is a fundamental hurdle in the realization and operation of nanostructured materials and high surface area microsystem architectures. These include such nano-interaction-based phenomena as self-assembly, fluid flow, and interfacial tribology. The proposed research utilizes photosensitive molecular structures to tune such interactions reversibly. This new material strategy provides optical actuation of nano-interactions impacting behavior on both the nano- and macroscales and with potential to impact directed nanostructure formation, microfluidic rheology, and tribological control

Stimuli-responsive materials: developing integrated opto-molecular systems as sensors and actuators in micro-fluidic devices

Micro-fluidic platforms have been conferred with inherent optical sensing capabilities by coating the walls of micro-fluidic channels or micro-capillaries with stimuli-responsive materials. These adaptive materials respond optically to environmental stimuli, such as changes in pH, solvent polarity, the presence of certain metal ions and light. This approach confers sensing capabilities along the entire length of the coated micro-channel or micro-capillary. Adaptive coatings based on two types of materials are presented: 1. Conductive polymer polyaniline - The optical properties of these coatings respond to changes in the pH of the solution that is passing through the micro- channel or micro-capillary, and therefore can be used for dynamic pH monitoring (pH 2-8) or for aqueous ammonia sensing. 2. Photochromic spiropyrans - Photoswitchable coatings based on spiropyran are used to photo-detect solvents of different polarity when passing through the micro-capillary in continuous flow. This sensing behaviour can be switched on/off remotely using light. Finally, it is reported, for the first time, the potential of using spiropyran as a pH pump in fluidic channels for photo-activated chemopropulsion of organic droplets and the solvato-morphological control of self-assembled micro-structures based on spiropyran