Microanalysis of clouding process at the single droplet level

We have applied laser tweezers equipped with a position sensitive photodetector (PSD) to investigate the clouding process in individual droplets with micrometer to nanometer in radius. The employment of PSD ensures a highly sensitive and non-intrusive detection for micro or nanodroplets. Systems as...

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Bibliographic Details
Published in:Sensors and actuators. B, Chemical Chemical, 2007-12, Vol.128 (1), p.154-160
Main Authors: Luchette, Paul, Abiy, Nebiyu, Mao, Hanbin
Format: Article
Language:English
Subjects:
Agglomeration
Clouding point
Clouding process
Droplets
Elastin
Globules
Laser tweezers
Lasers
Microanalysis
Microdroplet
Micrometers
Nanodroplet
Nanostructure
PNIPAM
Single droplet
TEA
Trapping
Triethylamine
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Summary:We have applied laser tweezers equipped with a position sensitive photodetector (PSD) to investigate the clouding process in individual droplets with micrometer to nanometer in radius. The employment of PSD ensures a highly sensitive and non-intrusive detection for micro or nanodroplets. Systems as diverse as triethylamine (TEA, a small molecule), poly( N-isopropylacrylamide) (PNIPAM, a polymer), and protein elastin, have been studied using this method. Compared to widely used approaches such as UV–vis determination of clouding temperature, our methods have shown an improvement of at least two orders of magnitude in detection limit. The trapping of droplet by laser tweezers creates a wall-less environment to prevent surface effects. In addition, it avoids gravity implications that interfere with bulk investigations on the clouding transition. The capability of our method is further demonstrated by an unambiguous observation that PNIPAM droplets in the clouding process grow through intermolecular aggregation after following coil to globule transition in the polymer.
ISSN:0925-4005
1873-3077
DOI:10.1016/j.snb.2007.05.048