Digital Microfluidic Chip


#21

Regarding SU-8 fabrication, there are pretty detailed (and accurate) recipes available here: http://microchem.com/Prod-SU82000.htm (scroll to the bottom and select the correct product).

The bubbles you see during heating are probably popping if you do not see them after the bake step. I had this happen often, and you can sometimes even use wafer tweezers to pop them manually. I don’t know if vacuum would work to remove them- it’s best not to get bubbles in the first place. Since the SU-8 has volatile solvents in it, you may see a lot of bubbles when you put it under vacuum because vacuum may speed up the volatilization of the solvent. I had this problem previously when trying to de-gas a hard polymer resin, and actually ended up with more bubbles in my resin than before the de-gas/vacuum step.

Mindy

···

On Thursday, March 12, 2015 at 3:20:28 PM UTC-7, Csaba Konrád wrote:

Thanks!

On Thursday, March 12, 2015 at 5:09:28 PM UTC-4, Ryan Fobel wrote:

A number of people here have also started using Fluoropel instead of Teflon-AF. I haven’t done a thorough characterization yet, but there doesn’t seem to be much of a difference in performance.

-Ryan

On Thu, Mar 12, 2015 at 5:05 PM, Markus Haapala mark...@gmail.com wrote:

Hi,

Cytonix Fluoropel solutions are a cheaper option for Teflon AF. See

http://www.cytonix.com/fluorosolpoly.html

We got 200 g of Fluor0pel 1604V (4% solids in solution) for 1000 $.

Br,

Markus

12.3.2015, 22:46, Michael Connolly kirjoitti:

Sigma-Aldrich sells Teflon AF in smaller quantities:

PTFE AF 1600 1G = $372 USD

http://www.sigmaaldrich.com/catalog/product/aldrich/469610?lang=en&region=US

as well as

PTFE AF 2400 1G = $387.59.

http://www.sigmaaldrich.com/catalog/product/aldrich/469629?lang=en&region=US

–Michael

On Thursday, March 12, 2015 at 12:52:46 PM UTC-7, Csaba Konrád wrote:

Hi,



I asked for the CEP at Biddle sawyer, its 100$ for 100 grams, not

so bad. The dimethyl formamide and the plasticoat 70 are also

cheap

([https://www.whitworths.com.au/main_itemdetail.asp?cat=123&item=33738&intAbsolutePage=](https://www.whitworths.com.au/main_itemdetail.asp?cat=123&item=33738&intAbsolutePage=)

<[https://www.whitworths.com.au/main_itemdetail.asp?cat=123&item=33738&intAbsolutePage=](https://www.whitworths.com.au/main_itemdetail.asp?cat=123&item=33738&intAbsolutePage=)>)


My only problem is that Dupont does not sell in small quantities.

If I get some  CEP would any of you guys be interested in trading

some for a small amount of teflon AF powder or solution with which

i can test out if i can make my own devices?



Best,

Csaba



On Thursday, March 12, 2015 at 12:08:07 PM UTC-4, Csaba Konrád wrote:



    Thanks!



    On Thursday, March 12, 2015 at 11:03:33 AM UTC-4, Sebastian > > > >  > > > >         vdE wrote:



        Q: Where do you buy it?

        A: I guess micro resist is our source of SU-8 and mr-L,

        but I don't buy it, i just "misuse" the resist as a

        dielectric layer.



        Q: Get rid of the bubbles?

        A: A lot good point, the pre-heating and the slow-heating

        might be worth a try! The vacuum is my next step anyway, I

        will try to use our vacuum oven: heating and vacuum at

        once. I copy the protocol from our cleanroom team, they

        are working with SU-8 and mr-L since years, I'm quite new

        with it. So their protocol should be kind of optimized.



        Q: Layer thickness measurement?

        A: The numbers I gave you are from our protocol, that

        means, I didn't measure them myself. At the moment the

        chips are stable (dielectrics are thick enough) and the

        bubbles are my problem. But if I want to measure, I can

        use the ellipsometer, the white light interferometer or

        just scratch it and measure the uneveness. Depends on the

        expected thickness and if I want to destroy the probe or not.

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