I am trying to fabricate simple microfluidic devices using common laser printer transparencies (polyester based). I will cut my channels using a CO2 laser, and then cover the same with 3mm acrylic sheets (with access holes).
I am not able to decide what would be a good method to bond the assembly. Most of the techniques involve sophisticated methods using expensive solvents, instruments etc. I want to use a simple, fast method with quick turn around and hopefully no distortion in channel dimensions. I would be grateful if somebody may help.
I have a hydraulic press, oven and access to chemicals such as chloroform, ethanol etc.
Thanks!
Hello
I think you can try this;
- Put 2 acrylic pieces on top and compress well between two aluminium material by screwing.
- Than put this setup on a hot plate to heat 100-200C for 30 minutes.
- Optimisation of temperature and time may be required for your case.
- We tried this before for PMMA-PMMA bonding and it worked but sorry I could not find the photos.
Best wishes
Serhat
www.nehirbt.com.tr
If you only require to form a cell made out of 3mm acrylic sheets that contains the microfluidic channels then the above answer is apt.
But if you are looking for something else then please specify
Hi Jashan, I want to have a 3 layer system with a transparency in the middle. The thermal bonding procedure described above leads to channel variation of upto 20-30 % at times.
A quick and easy way I had used earlier was using nuts and bolts, but that poses problems when you have a complex system. A simpler method could be using some adhesives or solvents, but they are difficult to find in India.
Hi there!
Given the set of equipment you have access to, if it were me, I would opt for dual-sided silicone pressure sensitive adhesives (PSA) for the PMMA-polyester-PMMA bonding. Depending on the channel wettability and the height dimensions you may require, you can laser cut the PSA according to either the PMMA pattern or the transparency film patterns (i.e. whether the fluid directly contacts PMMA vs silicone, and whether the extra height from the thickness of the PSA affects your fluid dynamics)
Note: always have the PSA adhered one of its side to the PMMA/transparency film and laser cut them together, so you won't have much problems with layer alignments later on.
Hope it works for you!
Best wishes,
Afiq
Hi Afiq,
Thank you for your answer. Is there a standard protocol for applying adhesives that you may suggest. I have gone through some of these but everyone uses a different technique, and I can't decide on one.
Thanks!
Hi Rohan,
I usually start from one side, and peel off the backing slowly as the adhesive start sticking to the surface (similar to applying a smartphone screen cover). if you have a roller, you can use it to remove air bubbles more efficiently as you stick on the adhesive.
I am aware there are people who remove the entire backing first and then applying PSA straight onto the plastic surface, but I don't do this because I'm not confident that I won't trap air bubbles or dust in between the layers. But that too is acceptable.
note 1: clean your plastic surface first before applying adhesives, you don't want dusts in between your layers.
note 2: if you don't want to waste PSA (they are a bit more expensive than normal tapes), you can practice with office Scotch tapes until you can do it well without trapping dust/bubbles.
Good luck!
Afiq
Hi Rohan,
A friend of mine suggested that if the sandwiching between the 3mm PMMA pieces is not completely necessary to the microfluidic design and you're able to use multiple layers of transparency films instead, the print-cut-laminate (PCL) method might be a better solution (see link). You will need to purchase an office laminator for it, but it's a more reproducible strategy.
Best wishes,
Afiq
http://www.nature.com/nprot/journal/v10/n6/full/nprot.2015.051.html
Lots of good suggestions here. Just want to mention that the channel size variations you've seen in the thermal bonding process is likely due to the temperature/pressure. We bond PMMA to PMMA slightly below Tg (107 C). This always takes a little optimization between devices, but around 102-105 C for 30 min-2 h should yield a good bond with minimal channel variations. Try sandwiching your assembly between glass plates and use "strong" binder clips to provide the pressure. All of that comes with a disclaimer that I don't know how well the PMMA will bond to the transparency film at those conditions.
PS - I've had great success with this solvent bonding recipe for PMMA (http://pubs.rsc.org/en/content/articlepdf/2006/LC/B512179E)
http://iopscience.iop.org/article/10.1088/0960-1317/26/6/065017/meta
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