by Rachel Aronoff
Urs Gaudenz of Gaudi labs provided the perfect hands-on experience for newbies to microfluidics at GOSH2018 during the first unconference sessions of the meeting. Microfluidics can be useful for many analyses, for instance of single cells, for making microdroplets and even for some DNA studies. Using a simple acrylic rectangle with 4 small holes, some wide cello-tape and couple of syringes and colored fluids, people got to make channels and explore the world of microfluidics ‘‘chips.’’
The holes in the acrylic were bored into the material with a laser cutter prior to the workshop and were made the same size as the ends of the syringes. First, protective layers were taken off each side of these rectangles, and on the table, the wide cello tape was put together in two layers and then stuck onto one side of the acrylic piece. Then, peoples’ imaginations and a box cutter were used to carve channels into the tape. Urs advised that one should avoid making these too wide, because, after the channels were cut, a third layer of the wide tape was then used to complete the microfluidic device. If the channel width was too broad, the third piece of tape could cause blockage of the fluidic path. Avoiding bubbles was somewhat tricky, but some simple pressure, pushing the cut tape on the acrylic chip down onto the third layer of tape, rather than vice versa, allowed the final layer of the chip to be constructed.
Using syringes loaded with the colored liquids (red and blue), the channels could then be tested. Some gorgeous examples were seen! Making these ultra cheap and easy microfluidic chips was a great experience. Microfluidics will be further investigated tomorrow by Urs tomorrow with participants, using a CNC router to cut channels.
Microfluidics uses an acrylic plate called a “chip” to help analyse things like DNA
To make one we can use common cellophane / packing tape, on top of acrylic cut using a laser cutter or router, the acrylic sheet or “chip” is covered with a sheet of waxy film called Parafilm which is commonly available and used in most labs everywhere.
Start with two layers applied flat on top surface of the acrylic piece or “chip”
Use a paper / box cutter to cut channels, any shape as required by the study / experiment.
then complete with a third layer of tape on top to seal in the channel.
try to make sure there are no layers.
q: diameter of the hole on the acrylic is the same
q: you make a channel starting from the hole
yes could go anyplace, commonly to another hole
q: how do we make the cuts
demonstrating the cuts: make sure you have 2 parallel lines to form the channel,
not too wide to make the top layer not close the channel between the cuts.
cnc router can also be used to form channels, but the focus here is to keep it really low cost
putting on the 3rd layer, try to flatten it out by inverting on a flat surface.
to run the fluid, add a drop to the hole and use a syringe to pull rather than push to have the fluid flow through the channel
peristaltics pumps can also be used to draw the fluid through the channels
q: is the tape glue toxic
bacterial influence is a concern if the use case is medical in nature
q: was this done by hand: double acrylic layer demo sample
laser cutter and double sided tape to form the double acrylic demo example
q: what to do if there are air bubbles or wrinkles, bad cuts?
its low cost tape so just remove the tape and try again
q: can I do it again
yes you can, remove the tape and do it again
q: why is this yellow: double acrylic layer sample
its made with double sided Kapton tape which is yellow but its hard to find double sided
q: what’s kapton tape normally used for
it’s a heat resistant material so it’s commonly wrapped around wires and things inside hot places.
you can buy the tape at 3d printer shops they used them to wrap cables that get hot at the 3d printing head or nozzle
Most participants enjoyed the process of constructing the chip and working with the red coloured water to watch it being drawn into the channels they created.
common issue people face is there’s too much pressure and leads to what participants jokingly have started to call “micro flooding” because it creates a tiny but fun little mess
You can have channels designed to use capillary action to draw up fluid instead of using a pump or syringe, basic physics at work with syrface tension of the fluid causing the flow.
Participants re-worked their chips, getting creative with design patterns and some working them to perfection, taking their first microfluidics with them when the session wrapped up.
Urs will be doing another session tomorrow but with a CNC router instead of just paper cutters.