Enzhu,
   Try World Precision Instruments www.wpiinc.com 941-371-1003.
They have microfil needles which are made of plastic and fused silica so
they are flexible.  They are sold as needles (with a luer lock) but you can
buy them 50cm long and cut them.  They are moderately transparent.
Glen

At 07:47 AM 12/4/2002, you wrote:
>Dear researchers,
>
>I am going use tiny tubes for fluidic devices. I prefer outer=
>  diameter~200um, inner diameter ~100um.I don't care about the=
>  materials. Are they commercially available?
>
>Sorry to bother again. Thank you so much.