Hi all,

I run a biochem lab; we do fluorescence microscopy in home-made fluidic flow-cells which we make by sandwiching together two borosilicate coverglasses, separated with a 0.5 mm spacer. The spacer (the gasket) is a small (24x40 mm) rectangle of 3M double-sided 4905 VHB tape, 0.5 mm (0.020") thick. We cut channels in this tape using a sterile disposable scalpel; the channels are about 1 mm wide and 5 mm long. We've been using this 4905 tape for nearly 15 years, and have been quite happy with it. The only problem is that foam material of the tape (the non-adhesive 'bulk') is somewhat toxic to our enzymes, which sometimes affects long-term measurements. Thus, I am thinking to get a thinner analog of the VHB (it comes in 25-50 micron sheets), and make the gaskets by sticking two thin double-sided tapes onto the two sides of a 0.5 mm virgin polypropylene sheet. This would reduce the surface of the exposed bulk tape 5-10 fold, which should help with the toxicity. I tested the adhesive with the PP, and it was fine. PP has been the 'default' bio-compatible material in my field for almost 40+ years.

However, I am not sure how to cut *cleanly* channels in the the PP-adhesive gasket. The scalpel method does not work b.c. it distorts the flatness of the plastic sheet, and it no longer sticks to the flat coverglass. We cannot use heat >150C, b.c it oxidizes the PP (no CO2 laser cutting). We cannot have significant burr and meltback, b.c. this prevents the flat coverglases from sealing properly. We cannot cut the channels using an endmill, b.c. this introduces cutting oil and fluorescence contamination. A die cutter might work, but I probably would have to sterilize it each time, or clean the die in a special way.

I apologize for the long message; I was trying to define the param space. Any suggestions would be appreciated.