[labnetwork] PDMS mold process?

[Eric Johnston]

Hi Russ

We have a separate room in our cleanroom dedicated to PDMS mixing and
molding. We have gloves of a very different color in that room which are
required to be worn when working with PDMS and are required to be removed
before exiting the room. Only the fully cured devices, cut out and with
inlet/outlet ports already punched out, may be removed from the room. That
said, most researchers use PDMS in their own (non-cleanroom) labs with very
satisfactory results.

Regarding "gotchas", including tips and tricks, here are a few:
- Be sure to mix the two components VERY well, like for 5ish minutes. If
they are not mixed well, the cured PDMS may stick to the master.
- An aluminum tray that can accommodate a wafer is very helpful. We got
ours from Kitchendance.com, item #80063, which is big enough for a 4" wafer.
- A 1mm biopsy punch is a great way to add inlet/outlet ports.
- The main cause of failure of the master, next to delamination, is
cracking of the wafer.
- It is easier to cut out only the devices needed. Trying to remove the
wafer from the PDMS mold can easily crack the wafer.
- "Silanizing" the master can make it easier to remove the mold. We
use Trichloro(1H, 1H, 2H, 2H-perfluoro-octyl) silane in a vacuum
desiccator. This is really only necessary if there are small features with
high aspect ratios.
- A drop of IPA when removing the PDMS mold can be very helpful. It acts as
a lubricant.

Regards

Eric

Eric Johnston
Director, Quattrone Nanofabrication Facility
Singh Center for Nanotechnology
University of Pennsylvania
3205 Walnut Street, #109A
ericdj at seas.upenn.edu
T. 215.573.6695
Questions? See the QNF FAQ
<https://wiki.nano.upenn.edu/wiki/index.php?title=Frequently_Asked_Questions#How_do_I_get_started.3F>
.

On Thu, Sep 4, 2025 at 8:08 AM Russ Renzas <rrenzas at unr.edu> wrote:

> Is anyone familiar with PDMS (or other material) mold fabrication? Any
> procedures or gotchas to worry about?
>
> Bio faculty member asking if we can make molds in our fab. I only know how
> to make semiconductor, photonic, and quantum devices.
>
> Thanks!
>
> Russ
>
> Russ Renzas
> University of Nevada, Reno
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