Dear Asfer,

I always have that problem. I think reuse the PDMS channels is tough.
Nevertheless, I have tried with Pluronic and it works for me long
enough for data acquisition. The following is an extracted paragraph
from my conference manuscript. Hope this helps.

"Carboxyl fluorescent Nile red beads (CFP-0556-2 Ex/Em = 532nm/556nm,
400nm to 600nm in diameter, Spherotech Inc., USA) were used in the
velocity measurement. The stock solution of 1% w/v was further diluted
in Pluronic F-127 (Sigma-Aldrich, USA) 0.05% w/v in HBS-N buffer from
0.05% to 0.4% w/v bead concentration to obtain a monodisperse
suspension. The aqueous HBS-N buffer (pH 7.4) was prepared by mixing
0.1 M HEPES and 1.5 M Sodiumchloride (NaCl), filtered through 0.22 µm
filter (MN Sterilizer PES, Macherey-Nagel, Germany). The suspension in
Pluronic buffer also prevents the non-specific binding of the tracers
to the cover glass surface or PDMS channel during observation"

Greetings,
Nam Le
Ritsumeikan University, Japan

On Wed, Jun 4, 2008 at 8:23 PM, Mohammed Asfer  wrote:
>
> Dear all
>
>    I am using carboxylate modified micro spheres(1.0 um, nile red
>    fluorescent, Invitrogen, molecular probes) for microPIV
>    measurements for flows through the microchannel made of PDMS. But
>    during flow, some of the the above fluorescent microspheres stick
>    to the walls of the PDMS channel. As a result it becomes
>    difficult to reuse the above channel. So can anyone tell me what
>    solvents can be used to dissolve those particles from the channel
>    walls without any changes in the microchannel features.