Small-scale device that generates, mixes, and reacts droplets in one place is an important step towards a miniature laboratory, say US researchers. 

Microfluidic systems use liquids in small quantities. When brought together, the small droplets mix much more efficiently than in larger volumes. Advantages over conventional bulk mixing include use of less-specialised equipment, fewer materials and less energy. 

Abraham Lee and colleagues at the University of California at Irvine have designed a system that measures, mixes and reacts starting materials before collecting and analysing the products - all in one place. This is an important development, says Lee, because high levels of control can be exercised over the whole synthetic process.

Through controlling the liquid flow rates precisely, a wide range of stable droplet ratios is possible for the two reactants. Lee demonstrated the mixing ratio and concentration control of the system by synthesising CdS nanoparticles. Analysis of the particles showed them to have regular particle sizes, a further advantage over bulk mixing. 

The device is a step towards producing a micro total analysis system that can carry out all operations normally performed in a laboratory including synthesis, processing, purification, and analysis on one microfluidic device efficiently and economically by using minute amounts of solvents and reagents, said Lee.  

Sue Askey