Stefania Mazzitelli and Claudio Nastruzzi,
Department of Life Sciences and Biotechnology, University of Ferrara, Ferrara, Italy
Why is this useful?
An event any microfluidic researcher never wants to occur is channel clogging. Unfortunately this drawback is not unusual, especially when working with narrow channel microchips and polymeric solutions or cell suspensions. On many occasions, microchips perfectly fitting the experiment appear to be irremediably lost and on the way to the rubbish bin.
Presented in this tip is a very simple and inexpensive solution that can revitalize a clogged microfluidic chip. We have tested this simple protocol both on glass or PDMS microchips with positive results, moreover we solved severe clogging (as evidenced by optical microscopy) caused by cell clustering as well as by the frequent occurrence of polymer precipitation within the microchannels. Our method solves the issues reported above using an extremely simple approach and a microwave oven.
What do I need?
- 21 gauge hypodermic needle 
- Plastic tube (ETEF, FEP or PTFE) 1/16” OD, 0.75mm ID 
- A 50 mL syringe 
- A microwave oven
What do I do?
1–5 Using the 21 gauge hypodermic needle and the FEP (fluorinated ethylene-propylene) tube, build up the plastic port for microfluidic interfacing (the needle should fit perfectly in the FEP tube assuring a tight, fluid proof inlet, see panel 4).
6–9 Insert the FEP tube into a microfluidic port. Depending on the position of the clog (determined by microscopic observation) insert the tube in the port as far away from the clog as possible.
10–12 Pump, by hand held syringe, filtered distilled water into the chip, applying as much pressure as possible. In the clog is constituted of lipophilic materials or hydrophobic polymers, replace the water with ethanol, isopropanol, acetone or their mixtures with water.
13 Put the microfluidic chip into a standard kitchen microwave oven for 5 min at 500-700 watts.
NOTE: before treating the chip in microwave, REMOVE the metallic needle or the entire port.
14–15 Remove the microfluidic chip from the microwave oven, reinstall the port and flush, as soon as possible, water (or solvent) into the channels. In case one treatment in the microwave does not open up the channels, repeat the entire procedure.
16 Your beloved chip is now open and ready for a new set of experiments.