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A microfluidic lab -on -a -chip (LOC ) device for in -situ synthesis of gold nano -particles
was developed . The long term goal is to develop a portable hand -held diagnostic
platform for monitoring water quality (e .g . , detecting metal ion pollutants ) .
The LOC consists of micro -chambers housing different reagents and samples that feed to
a common reaction chamber . The reaction products are delivered to several waste
chambers in a pre -defined sequence to enable reagents / samples to flow into and out of
the reaction chamber . Passive flow actuation is obtained by capillary driven flow
(wicking ) and dissolvable microstructures called ‘salt pillars’ . The LOC does not require
any external power source for actuation and the passive microvalves enable flow
actuation at predefined intervals . The LOC and the dissolvable microstructures are
fabricated using a combination of photolithography and soft lithography techniques .
Experiments were conducted to demonstrate the variation in the valve actuation time
with respect to valve position and geometric parameters . Subsequently , analytical models were developed using one dimensional linear diffusion theory . The analytical
models were in good agreement with the experimental data . The microvalves were
developed using various salts : polyethylene glycol , sodium chloride and sodium acetate .
Synthesized in -situ in our experiments , gold nano -particles exhibit specific colorimetric
and optical properties due to the surface plasmon resonance effect . These stabilized
mono -disperse gold nano -particles can be coated with bio -molecular recognition motifs
on their surfaces . A colorimetric peptide assay was thus developed using the intrinsic
property of noble metal nano -particles . The LOC device was further developed on a
paper microfluidics platform . This platform was tested successfully for synthesis of gold
nano -particles using a peptide assay and using passive salt -bridge microvalves .
This study proves the feasibility of a LOC device that utilizes peptide assay for
synthesis of gold nano -particles in -situ . It could be highly significant in a simple
portable water quality monitoring platform . |
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