Materials

• PDMS monomer and curing agent (Sigma-Aldrich, Sylgard 184, 761036-5EA)
• Mold (epoxy resin or aluminium)
• Isopropanol for cleaning purposes
• Scale (Kern PCB 1000-2)
• Plastic beaker
• Vacuum pump unit (Vacuubrand PC 3 RZ 2.5)
• Vacuum bell jar (Kartell desiccator)
• Spatula
• Stove (Memmert UM 400) at 70 degrees Celsius
• Paper (Kimberly-Clark SCOTT Blue)
• Gloves (Kimtech Science PFE)

Procedure

According to the Sylgard 184 manual.

1. Pour PDMS monomer into a beaker.
2. Pour curing agent into the same beaker (10:1 proportion: 1g for 10g of monomer).
3. Mix with the spatula for 30 seconds. Spatula can be cleaned afterwards with some paper dipped in isopropanol.
4. Put beaker into the vacuum bell jar connected to the vacuum pump unit in order to extract the air bubbles from the mixture (at least 10 minutes vacuum, look out for overflowings).
5. Pour mixture onto mold.
6. Put mold+mixture in stove at 70 degrees Celsius for 3 hours at least.

Materials

• Razor blade (OEMTOOLS 25181 Razor Blades, 100 Pack)
• Biopsy puncher (Kai Biopsy Punch 4mm )

Procedure

1. Use a razor blade to cut the borders of the chip and extract the PDMS from its mold. Avoid touching the circuits on your chip to avoid unwanted fingerprints.
2. Drill input and output holes with the biopsy puncher.

Get the PDF version of this protocol

In some cases, before using your chip, you'll need to seal the circuitry. In order to do that, it is common to use plasma bonding to glue the chip to another surface (PDMS or glass).

Materials

• Plasma cleaner (Diener Pico PCCE)
• Distilled water
• Isopropanol for cleaning purposes
• Office duct tape
• Fume hood (Euroclone aura vertical S.D.4)

Procedure

1. First, the chip needs to be cleaned in the fume hood. To do so, apply duct tape onto the surface of the chip you want to bond and remove it. Clean the chip with isopropanol.
2. Put the chip and the surface you want to bond it to into the plasma cleaner. The surfaces you want to bond need to be facing up in the machine in order to be exposed to plasma.
3. Expose chip and surface 30 seconds to plasma.
4. Take the chip and the surface back in the fume hood.
5. You have 20 minutes to execute this step. Press the microfluidic chip against the surface. The surfaces that need to be glued together need to face each other. If bonding failed, repeat from step 1.

Materials

• Poly-D-Lysine (Sigma-Aldrich, Poly-D-Lysine solution, 1.0 mg/mL ,A-003-E)
• Laminine (Sigma-Aldrich, Laminin from Engelbreth-Holm-Swarm murine sarcoma basement membrane, L2020-1MG)

Procedure

1. Pour poly-D-lysine with concentration 10 $\mu$g/mL into the chip and incubate over night.
2. Then pour laminine with concentration 4 $\mu$g/mL and incubate for a few hours.

An aqueous solution of PEDOT :PSS can be prepared [1]. We decided to dip the membranes in this solution during the polymerization.

[1] Jikui Wang, Guofeng Cai, Xudong Zhu, Xiaping Zhou, Oxidative Chemical Polymerization of 3,4-Ethylenedioxythiophene and its Applications in Antistatic coatings, Journal of Applied Polymer Science, 2012, Vol. 124, 109-115 .

Materials

• EDOT (3,4-Ethylenedioxythiophene, Sigma-Aldrich, 483028-10G)
• PSS (Sodium 4-vinylbenzenesulfonate, Sigma-Aldrich, 94904-100G )
• Deionised water
• Sodium persulfate (Sigma-Aldrich, 216232-500G)
• Iron(III) sulfate hydrate (Sigma-Aldrich, F0638-250G)
• Alumina Oxide Membrane Filters, 0.2 micron pores, 13 mm (Sterlitech) (figure 1)



• Stripette (Corning Costar, 5 mL) + pipette filler
• Analytical balance (Mettler Toledo NewClassic MF ML204 /01)
• Magnetic stirrer with heating plate (yellowline MSH basic)
• Fume hood (Delagrave SA OPTIMUM 1500)
• Gloves
• Forceps (Bochem art. 1013)
• Glass beaker (600 mL)
• Petri dish

Procedure

1. Pour 0.8 g EDOT, 2g PSS and 208 mL water in the glass beaker.
2. Put the membranes in the solution.
3. Stir for 10 minutes (figure 2).



4. Add 2 g of sodium persulfate and 0.015 g of iron(III) sulfate hydrate.
5. Stir for 24 hours (figure 3).



6. Wash membranes with water and let them dry at room temperature in a Petri dish. (figure 4)

PEDOT :Ts and PEDOT :Cl polymers can be obtained by vapor phase polymerization on alumina oxide membranes [1].

[1] Alexis E. Abelow, Kristin M. Persson, Edwin W.H. Jager, Magnus Berggren, Ilya Zharov, Electroresponsive Nanoporous Membranes by Coating Anodized Alumina with Poly(3,4ethylenedioxythiophene) and Polypyrrole. 2014, 299, 190-197.

Materials

• EDOT (3,4-Ethylenedioxythiophene, Sigma-Aldrich, 483028-10G)
• Iron(III) p-toluenesulfonate hexahydrate for PEDOT :Ts (Sigma-Aldrich, 462861-25G) or Iron(III) chloride for PEDOT :Cl (Fischer Scientific, 217091000)
• 1-butanol (Sigma-Aldrich, B7906-500ML)
• Deionised water
• Alumina Oxide Membrane Filters, 0.2 micron pores, 13 mm (Sterlitech) (figure 1)



• Paper masks (figure 2)



• Stripette (Corning Costar, 5 mL) + pipette filler
• Analytical balance (Mettler Toledo NewClassic MF ML204 /01)
• Magnetic stirrer with heating plate (yellowline MSH basic)
• Fume hood (Delagrave SA OPTIMUM 1500)
• Gloves
• Forceps (Bochem art. 1013)
• Glass beaker (600 mL)
• Petri dish

Procedure

1. Prepare homogenous oxidant solution (1.58 g Iron(III) p-toluenesulfonate hexahydrate and 10 mL butanol for PEDOT:Ts (figure 3) or 1.35 g Iron(III) chloride and 10 mL butanol for PEDOT:Cl (figure 4)





2. Dip membranes in oxydant solution.
3. Let membranes dry at 40◦C (figure 5).



4. Place membranes in paper masks on Petri dish lids (figure 6) .



5. Pour 200 µL EDOT in 50 mL beakers.
6. Place Petri dish lids on top of the 50 mL beakers, membranes facing the inside of the beakers.
7. Heat the beakers at 40◦C and stop when membranes darken (takes about 6 minutes) (figure 7).



8. Wash membranes with butanol and water.
9. Let membranes dry at room temperature (figures 8 and 9).

Molds were made of aluminium according to the following plans. Part 1 Mold's center cylinder part is detachable from the bottom to make the demolding ot PDMS easier.

Materials

• Molds
• Syringe (Terumo syringe without needle, 10 mL )
• Platinum 24 mm x 2 mm strip (mechanically flattened 24mm long 0.7mm diameter platinum wire)
• Polycarbonate gold-coated membrane filters, 0.4 micron, 13mm diameter (Sterlitech) or polymerized membrane see protocol

Refer to sections 1 and 2 of Microfluidics: general protocols for further needed materials.

Procedure

1. Prepare 20 g of PDMS monomer using section 1 of Microfluidics: general protocols .
   Replace step 5 by: Fill the syringe with PDMS. Fill part 1 mold until it's full and part 2 mold until the PDMS layer is more or less 1 cm thick. Keep the PDMS that is left.
2. Demold the chip following section 2 of Microfluidics: general protocols . Ignore step 2.
3. Put membrane and platinum strip on PDMS part 1. Refer to figure 1 for their position.



4. Refer to section 3 of Microfluidics: general protocols to bond PDMS part 2 to the PDMS part prepared in the previous step. It should look like figure 2.



5. Apply a small layer of PDMS with the syringe. Refer to figure 3 . This way, the well is watertight.



6. Put the chip in the stove for 3 hours.

Materials

• Oscilloscope
• Function generator
• Solderless breadboard assembly
• Electric wires with banana connectors
• Coaxial cable
• Male BCN to 2 female banana connectors converter
• BNC Splitter
• 1 kOhm resistor

Procedure

1. Reproduce the following electric circuit.



2. Set function generator on sine, no offset, 4.5 V amplitude.

We were allowed to use the molds made by Institut Curie. We were not involved in the process of their fabrication. Here is a short video we made about how these molds were created.