Microchemical single droplet reaction analysis by online cavity ring-down spectroscopy

Lead Research Organisation: University of Oxford
Department Name: Oxford Chemistry

Abstract

Microfluidics provides an exceptional environment for the generation of controlled droplet dispersions and their manipulation in prescribed flow fields. The spatio-temporal correspondence between microchannel position and reaction 'time' permits the study of kinetics of (chemical and physical) processes with unprecedented time resolution and dynamic range. Further, the combination of the small volumes of droplet 'reactors' and the precise formulation of their composition opens vast possibilities in chemical synthesis, including screening, discovery and optimisation. Monitoring reactions in real-time with non-invasive probes remains, hitherto, a major shortcoming of microchemical reactors due to the minute sample volumes (pL-nL) and fast travel speeds (1-1000 mm/s). This proposal seeks to develop, implement and validate a novel experimental approach to monitor microchemical reactions in real-time by coupling, for the first time, cavity ring-down spectroscopy and solvent-resistant microfabrication. This approach will permit the online study of model catalytic reactions, with unprecedented reproducibility and flow control. Cavity ring-down spectroscopy will permit the analysis of pL volumes, effectively eliminating the restriction of path length in microchannels, with nanosecond to microsecond time resolution, compatible with microreaction drops. In particular, we will elucidate individual and global reaction population outcomes and the effect of mixing and flow, with spatiotemporal resolution. This approach is applicable to a range of organic chemical reactions and, for this work, we will focus on selected model systems (detailed below) of fundamental and industrial relevance.
 
Description The original award was concerned with combining cavity ringdown spectroscopy with a sample contained within a microfluidic chip. Near the end of the grant period I began to collaborate with the group of Jason Smith in Oxford's Department of Materials, on combining optical microcavities with chemical sensing in microfluidic environments. This work grew directly out of work funded by the EPSRC, though was not part of the original grant. We have shown that we can achieve extremely sensitive measurements of refractive index and optical absorption (absorption spectroscopy) for liquid samples, and also that optical microcavities can be used to carry out detailed characterisation of nanoparticles trapped in the cavity.
Exploitation Route While the methods used in the original EPSRC-funded research proved to be quite difficult to use, the microcavity methods that have followed show considerable promise for a variety of applications. We are planning to form a spin-out company based on this technology over the next few months, in order to develop commercial instruments.
Sectors Chemicals,Education,Energy,Environment,Healthcare,Pharmaceuticals and Medical Biotechnology

 
Description Leverhulme Trust Project Grant
Amount £229,389 (GBP)
Organisation The Leverhulme Trust 
Sector Academic/University
Country United Kingdom
Start 03/2012 
End 03/2015
 
Description Paul Instrument Fund
Amount £72,635 (GBP)
Organisation The Royal Society 
Sector Academic/University
Country United Kingdom
Start 10/2012 
End 10/2014