Microfluidics with K40 laser cutter Part 5

I want to make microfluidics out of acrylic. Acrylic is stiff, resistant to a reasonably wide range of chemicals, and transparent. That means we can do chemistry in it and see what’s happening inside.

Acrylic is reasonably easy to cut with a laser. A $400 laser cutter can be purchased on ebay that will do the job. You get what you pay for, to some extent. It takes some effort to find an optimal cutting power and speed that give reproducible results.

Once acrylic is cut, it needs to be bonded. I have tried glue, double stick adhesive, and solvent welding. All bonded the acrylic but each has significant drawbacks. Glue and solvents both tend to wick into the channels. Solvents also tend to “craze” the surface and make it too opaque. Double stick adhesive tape introduces a new polymer to the system and is hard to handle. For larger features, we have had some success.

Ultimately, the best method to bond acrylic is to apply heat and pressure over some time. Heat should be 140-150 degrees C.  That’s enough to soften but not melt the acrylic. Acrylic held in close contact for 10-15 min at this temperature will bond. Pressure should be few PSI (we’re working on measuring this precisely). Too much pressure and the channels will collapse. That is by far the most frequent cause of failure.

With the right parameters, a good bond can be obtained. A little superglue will bind a hollow needle into an access port. And voila: microfluidics. Now I need to use this to make droplets again.

Here are parts 1 2 3 and 4.