I want to treat PDMS channels with it, but condensation does not treat the whole length of the channels. The only information I have is that the silane reacts violently with water. All of the protocols that I found involve evaporation and deposition. If you have some idea for dissolving this silane, please let me know.
Dear Elena,
To make microfluidic channels hydrophobic, we make a solution of 1 wt% FDTS in iso-octane.
Try an aqueous solution of Perfluorodecyltriethoxysilane. 2-4% should do the trick. This solution will need to be mixed fresh for every use and should be applied immediately after plasma bonding to take advantage of the activated surface.
Thank you for your answers. I found that this silane can be dissolved in methanol, which doesn't swell PDMS.
Hi Elena,
I think methanol slightly swells PDMS microchannels. If your experiments involve some measurements, then treating PDMS with methanol is detrimental. Please check the following article.
Solvent Compatibility of Poly(dimethylsiloxane)-Based Microfluidic Devices
DOI: 10.1021/ac0346712
I already checked it. The parameter describing expansion of PDMS because of water penetration is 1 (no expansion). That of methanol is 1.02.
Wikipedia: Alcohols and polar solvents such as methanol, glycerol and water do not swell the material appreciably.
I will try it some time.
I used this fluorophilic reagent for our water in fluorous oil picodroplet ESI MS chips. Then I used 0.5% trichloro(1H,1H,2H,2H-perfluorooctyl)silane in Novec7500 for about 5 minutes. I did this immediately after bonding the two halves of my PDMS together. Then wash out the channels with Novec7500 and then blow the channels out with air from a 1mL syringe. You could also use PicoGlide, which is made by Sphere Fluidics, which has much longer fluorous tails. This reagent takes about 40 minutes to make the channel walls fluorophilic.
We flush our channels with 1% mixture of trichloro(1H,1H,2H,2H-perfluorooctyl)silane in isopropanol for 6 minutes. Then we put it in the oven at 70 degC to evaporate the solvent- and it works pretty good, we did not observe deformation of the channels (determined by measuring channel widths before and after the treatment). Of course this will depend on the size of the channels- if they are very long and narrow and PDMS layer is thick, evaporation of isopropanol may be very slow.
Elena, assuming you have oxidised the surface of your PDMS device, usually with an oxygen plasma then you can react your reactive (water sensitive) trichlorosilane in most fluorinated solvents.Try buying from SigmaAldrich, Fluorochem or some other distributors. The most common solvents to use are Novec7500 also known as HFE 7500: http://www.fluorochem.co.uk/Products/Product?code=051243 or Fluorinert FC40, see: http://www.sigmaaldrich.com/catalog/product/sigma/f9755?lang=en®ion=GB Also, good for washing is HFE7100, which is much lower boiling, see: http://www.sigmaaldrich.com/catalog/product/honeywell/65139?lang=en®ion=GB Don't go above 0.5% vol:vol as you can see build up of by-products from the reaction in your channels. The reaction is very fast, 5 minutes is plenty, then wash with HFE7500 or 7100 and blow dry with a 1 ml syringe or use immediately. Open the bottle of the silane under nitrogen if you can, to keep the moisture out. Just make up small amounts of the 0.5% solution and then discard. These solvents have very low moisture content and so do not need further drying. Best of luck! Clive
Could you please help me out? I need to dissolve FDTS in hexane. How can I make an aqueous solution of it? like what is the ratio of FDTS to hexane?
I don't think FDTS will be soluble in 100% hexane, but if you dilute Novec7100, or perfluorocyclohexane or FC40. You can definiteky make a homogeneous mixture of 50% hexane:Novec7100. See links to purchase above. You only need a maximum of a 0.5% solution to modify the channels of your device. Leave for 5 minutes, seal device with scotch tape, then wash out with solvent and blow dry. Again when opening the FTDS, dru and do so under a blanket of nitrogen as it is very reactive with water and alcohols.
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