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

Lead Research Organisation: Imperial College London
Department Name: Department of Chemical Engineering


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.


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Description This project enabled the coupling of microfluidic devices with a spectroscopy for the detection of very small liquid volumes at very low concentrations. Microfluidics - the controlled handling of liquids in small volumes (pL-microL) - is a powerful platform for the synthesis, discovery and analysis of chemical, biological and physical sciences. It is particularly impactful in flow chemistry. To fulfill its potential, researchers need to measure, non-invasively and rapidly, reaction processes. While normal spectroscopy suffers from low signal (due to small sample volume), our optical cavity approach overcomes this challenge by effectively extending the sample size by several orders of magnitude. The coupling of these two approaches required the refinement of both microfabrication and optical cavities, and eventually resulted in a robust ultra-sensitive detection system for droplet flow chemistry with potential for: flow chemistry, drug discovery, marine science and bio-analytical and environmental sciences. So far, only visible detection was demonstrated, mono and polychromatic - this can be further extended to IR and UV depending on need.
Exploitation Route This approach can (and, in part, has already) be employed for high-sensitivity detection of composition and reaction kinetics in: flow chemistry and drug-discovery, marine and environmental sciences, as well as a within microfluidics platforms in general.
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Chemicals,Energy,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology,Security and Diplomacy

Description In partnership with Pfizer and Oxford University, this flow chemistry award enabled the development of the first microfluidic approach compatible with optical spectroscopy. The challenge of small path lengths (due to small sample volumes) has been overcome by employing optical cavities that 'bounce' light beams multiple times within a single volume. Visible light, both mono- and polychromatic has been demonstrated to measure composition and gauge reaction kinetics (and mechanism) in both continuous and droplet flows. We have demonstrated the approach with several model reactions with a fingerprint in the visible range. In concert with Pfizer, we evaluated reactions of interest in flow chemistry. Scientific publications defined the potential and limitations of the approach, as well as possible extensions with fibre optics, multiple diode lasers and white sources, and miniaturization for portability.
First Year Of Impact 2011
Sector Aerospace, Defence and Marine,Chemicals,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Security and Diplomacy
Impact Types Economic

Description Procter and Gamble research contract
Amount £200,000 (GBP)
Organisation Procter & Gamble 
Sector Private
Country United States
Start 08/2014 
End 08/2016
Title Microfluidic FPP devices 
Description Rapid prototyping method for microfluidic devices 
Type Of Material Improvements to research infrastructure 
Year Produced 2012 
Provided To Others? Yes  
Impact Inexpensive, accurate and rapid microfabrication approach available to a wide range of researchers 
URL http://www.imperial.ac.uk/polymers-and-microfluidics/research/micro-reaction-engineering/