The mold can be made in less than a day, but the mask (for the
photolithography) still takes time (a few days).  If there is a printer
than can print ~10 um high lines, that would obviously a lot faster.  And
why not prototype as fast as possible?

We are already investigating the use of thick resist.  Anyone happen to
know a set of conditions for patterning an AZ type resist at 10-20 microns
thick?

-Marc Unger
[email protected]

> One way to achieve this is to use a thick resist - something like AZ4620
> (I thinks Shipley also makes a thick resist?).
> This type of photoresist can be spun on with different thicknesses (up to
> 100um thick) by varying the rpm spin speed and time.  Therefore, you can
> use the masks you already have and do not need to etch away the
> substrate(unless you need deeper channels).  Another solution could be to
> use SU-8(the patternable one) which also has controllable thickness.
>
> Also, why do you say that the process is slow for prototyping?  It seems
> that the mold can be made in less than a day(even with etching), and the
> PDMS can be "molded" within a few hours.  Is this what you think is slow?
> Or is your etching taking a long time?  Le me know if you would like to
> discuss this more.
>
> -Angela Rasmussen
> The George Washington University
> The Institute of MEMS and VLSI Technologies
>
>
>  On Wed, 12 May 1999, Marc A. Unger wrote:
>
> >
> > Hi There -
> >
> > We're doing some "soft" lithography - i.e. PDMS casts of Si molds.  Up
> > until now, we've been patterning resist and doing bulk etching of Si to
> > make our molds.  This works fine, but it's kind of slow for prototyping.
> > Does anyone know a way to "print" a pattern 10-15 microns high directly
> > on a smooth substrate?  ("Smooth" is relative; things as rough as a
> > overhead transparency will probably still work.)  It would be a bonus if
> > the process allows adjusting the height of the lines.
> >
> > By the way, laser printers and thermal transfer printers seem to make lines
> > about 5 microns high.  So if anyone knows a way to make a laser printer
> > or thermal transfer printer print twice or three times on the same area,
> > that might be worth a try, too.
> >
> > I will summarize replies back to the list.
> >
> > Thanks in advance,
> >
> > Marc Unger
> > Caltech Applied Physics
> > [email protected]
> >
> >
>
>
>