We are using plastic cartridge for DNA extraction. The channels created in plastics need a valve which needs to select between two channels and direct fluids to selected channels. The movement of fluid is by vacuum pump.
Use Acrifix - see https://www.google.com/#q=Acrifix.
This is a family of specific acrylic glues. If not right the manufacturer will probably be able to provide specific solutions.
Acrylic polymers can be solvent bonded using methylene chloride. If the sheets are relatively smooth, place them in contact and apply the solvent to the edge using a syringe. Capillary action will draw the solvent into the gap between sheets. You can also dissolve a small amount of acrylic into the solvent to make a thicker solution which will fill small gaps.
I was going to suggest using solvent to bond the sheets as Jon did; it is an elegant approach and minimizes potential for adhesive blocking the small channels.
Instead of the syringe application of solvent (if the distances are too large), you might try local application of the solvent to the film surface and mild heat/pressure lamination. Since methylene chloride has such a low boiling point, this approach might be better using a higher boiling solvent. To reduce the amount of solvent, you might pick a water soluble one that has a higher boiling point than water and apply it to the acrylic film surface.
Use 5 - 20wt% of your solvent and allow the evaporation of most of the applied solution. You should end up with a plasticized (lower softening point) surface that will bond to the applied facing sheet under mild heat and pressure.
Acetone is a good solvent for acrylic sheets, and produces mechanically resistant joints.
We've had good results using acetone to solvent weld cm-scale channels and chambers, able to hold 5-6 bars of pressure (chamber area 2-3 cm2, bonded area of 3-4 cm2). Very simple and quick. Filling the bonding interface by capillary action works well when the distance that you need the acetone to travel is 5 mm or less from the edge. Farther than that, the solvent front is prone to "snagging" on surface imperfections and not fully penetrating into the gap.
If the bond joint is deep like this, I recommend first shimming the pieces 100-200 µm apart to create a small gap (rather than holding the parts in contact right at the start) and letting a slight excess of acetone fully flow into the gap. After this, applying a moderate pressure/weight results in a very high-quality void-free bond between the acrylic parts. The parts set in only a few minutes and can be handled with no problems after a couple hours. Will hold full pressure after waiting overnight.
I may suggest 3 methods which could be tried on very small scale to see if they work properly: 1) Using little epoxy resin (Two containers; one is small containing hardener & one is larger containing epoxy pre-polymer). It is fast-acting adhesive & was described by some scientists as (being able to bond anything to anything!). OR 2) Silicone grease which is relatively slow-acting. OR 3) Super Glue (which contains the monomer Methyl-α-cyanoacrylate that polymerizes fast by moisture to form a good adhesive).
As was suggested above, methylene chloride is an excellent choice. If you experience too much solvent getting into your channels then I would suggest vapor deposition of methylene chloride. Hold your samples over heated methylene chloride for couple minutes then bring the in contact with each other and let it dry under some pressure.
Alternative method is to use thermal bonding. Acrylic has very low glass transition temperature. The process is: heat samples (do not over heat) bring in contact, apply pressure, cool. Heated press is a very useful tool for that.
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