David Juncker, McGill, Bioengineering department (through Tibi, they worked together)
Mohammad Qasaimeh, PhD in bioengineering (through Tibi - friend)
Yves-Alain Peter, Ecole Polytechnique de Montréal (met once, probably will collaborate, ask Francois, Tibi, Ivan and Jonathan)

NOTE: please respect the link relations!

Other communities

Public Laboratory - Tibi is embedded

Applications

Precise molding of polymers, microfluidics, lab-on-a-chip.

For lab-on-a-chip fabrication one needs to integrate microfluidics, electronics and optics. PMMA would be a very good material to start with, because of its nice optical properties.

We already know how to coat PMMA with silver, using a low cost and environmentally friendly method, see protocol, see development document. This allows us to build actuators into the chip, to introduce electrodes, to write diverse circuits on it, etc.

For the photonic layer, we can work with PMMA optical fiber and connect that to the chip, which can have other components. See this publication.

Our work on etching

Jonathan is already using a classical copper etching technique for electronic boards, achieving resolutions under 500 microns.
June 05, 2013 Tibi played with aluminum etching using soduim hydroxid (NaOH).
June 07, 2013 Tibi used diluted ferric chloric acid (the same one used for copper etching on electronic boards) to achieve better results.

Masking using kapton tape and car paint

The sample used is aluminum.

Make a kapton tape mask on a polished and clean aluminum surface. The area covered will be the area etched.

Spray car paint on the entire surface to cover the remaining area. The painted surface will not be etched.

Use a hot plate or an oven to fast cure the paint.

Remove the kapton take to leave the paint

The aluminum part is dumped into the solution (soduim hydroxid or ferric chloride), contained in a glass container, on top of a spinning plate. The paint is easily removed using acetone.

Results with ferric chloride

Markings in the picture below are 0.5mm.

NOTE [tibi]: instead of the car paint, we also tried a permanent marker for masking, which is inert in the acid solution. The problem is that the market coating applies is porous and it get’s etched eventually. We want to etch over 200 microns deep, therefore the mask needs to be quite though.

Conclusion

We can definitely get under mm features on a low grade aluminum. In order to improve the precision of this technique we first need a finer grain aluminum. Second, in order to achieve a smoother etched surface we are going to try silica microspheres (supplier) into the acid solution and sonicate during the etching process. The acid solution needs to be agitated in order to remove the bubbles that form at the surface. Moreover, we also see a deposit on the surface as the etching progresses, and we believe that the silica microspheres agitated by ultrasound waves will keep the surface always clean.

Potential problem with sonication[tibi]: we tried to sonicate a sample, the problem is that the car paint used to mask detaches itself during the process. I guess the ultrasound is too rough on the paint coating.

Results with soduim hydroxid

1mm marks in the picture below.

The features on the surface are well within the 100 micron range.

Conclusion

The reaction seems to be OK. The NaOH doesn’t seem to react to the paint.

See other comments in the section above.

Other ideas for masking

Projection 3D printer

To be developed!

One can use a projection 3D printer to create a UV curable polymer mark. Low cost open source projection 3D printer: B9Creator (50 micron resolution).

Advantage - allows any shape to be patterned, and can be used on large surfaces. The mask is done in a single step from a picture file.

Disadvantage - requires at least 5K investment in a projection 3D printer (we already want to buy one!).

High power UV LED for masking

To be developed!

Possible supplier for UV LED

LED driver (we already have one that can drive high power LED, made by Frederic D)

UV curable polymer - see products from Norland, we already have in stock NOA 86 and 61

The mask can also be made from laser printing on cellophane.

Advantage - nice and low cost for fast prototyping, allows any shape.

Disadvantage - can only be used on small surfaces. requires an extra step to do the mask for the UV curing.

Water and grease for patterning

To be tested!

Use wet thin fibers on the metal surface to create a wet barrier. Pore (hot) liquid grease over the rest. The water around the fiber and the grease will not mix. Water surface tension and grease will create a straight line of separation. Cool the grease until solid. Remove the fiber and dry the remaining water on the surface. Spray paint. Remove grease. Etch.

Microspheres of silica

See wikipedia full article and references

The Stöber process is a physical chemistry process for the generation of monodispersed particles of silica. The process was discovered in 1968 by Werner Stöber et al.[1] building on earlier work by G. Kolbe in published in 1956.[2] The topic has since been widely researched. Tetraethyl silicate is added to an excess of water containing a low molar-mass alcohol such as ethanol and containing ammonia. The resulting solution is then stirred. The resulting silica particles have diameters between 50 and 2000 nanometers depending on type of silicate ester used, type of alcohol used and volume ratios.[3] A particle size up to 1000 micrometers has been reported in a modified emulsion technique.[4] The reactions taking place are hydrolysis of the silyl ether to a silanol followed by condensation reactions. The particles have been analyzed by light scattering.[5][6]

The process is believed to take place via a LaMer model (monomer addition) in which nucleation is a fast process, followed by a particle growth process without further nucleation.[7][8][9] In an alternative model called controlled aggregation, the particles grow by aggregation of smaller particles.[10][11][12][13][14] This model is supported bymicrogravity experiments [15] and by SAXS analysis.[16] Kinetics have been investigated with variation in pH.[17]

Reported morphological variations are a PEG graft [18] and core-shell morphologies based on cyclen,[19] polyamines [20] and polystyrene.[21]

Microporous silica particles can be obtained through organic templating followed by calcination. Reported organic additives for this process are cetyltrimethylammonium bromide[22][23][24] and glycerol [25]

Deposition

Our wet silver coating process

open protocol document

Other methods to explore

Electroplating

Electrophoretic deposition

Handbook of Thin-Film Deposition Processes and Techniques - Principles, Methods, Equipment and Applications (2nd Edition)