Supplementary information
Microfluidic Approach for the Formation of
Internally Porous Polymer Particles by Solvent
Extraction
Takaichi Watanabe,a,b Carlos G. Lopez,a Jack F. Douglas,c Tsutomu Ono,b João T. Cabrala*
a
Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK
b
Department of Applied Chemistry, Graduate School of Natural Science and Technology,
Okayama University, 3-1-1 Tsushima-Naka, Kita-Ku, Okayama 700-8530, Japan
c
Materials Science and Engineering Division, National Institute of Standards and
Technology, Gaithersburg, Maryland 20899, USA
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Fabrication of the microfluidic devices
Microfluidic devices were fabricated using a procedure reported previously.S1-S5 Briefly,
thiolene functions as a negative photoresist and its frontal photopolymerization nature
permits the patterning of optically clear devices in 3-dimensions with lateral resolution down
to approximately 50 m and vertical dimensions tuneable by light exposure. Thiolene was
polymerized between glass slides (Corning (75 x 50 x 1) mm3) with pre-drilled holes for
inlets and an outlet. Prior to use, the glass surfaces were treated with 10 mass % of
octadecyltrichlorosilane (OTS) / toluene solution for 1 h, followed by oven drying at 110oC
overnight, in order to render the surface hydrophobic. Acetate sheet spacers (100 m) were
placed at the four corners of the glass slides to enclose the photoresist and define the channel
height. Two identical negative photomasks printed on transparent acetate film using a
commercial laser jet printer (HP LaserJet M2727) were aligned and placed over the top of the
glass sandwich. The device was cured under the UV-A source at 140 W cm-2 for 2 min to 3
min. After removing the spacers, the uncured photoresist was flushed from the polymerized
matrix using ethanol and acetone on a hotplate at 65oC, followed by compressed air. The
device was then allowed to postcure at 140 W cm-2 without the photomask for an additional
30 min. Finally, nanoports (N-333 Upchurch) and tubing were placed over each hole and
epoxy adhesive (Araldite, Hunstsman) was used to attach the connectors to the device.
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SEM images of internally porous polymer particles
2.5% NaPSS
50 m
5% NaPSS
50 m
10% NaPSS
50 m
Figure S1. Additional SEM images of representative particles obtained from solvent
extraction of droplets of 2.5, 5 and 10 wt% NaPSS aqueous solutions immersed in MEK.
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100 m
Figure S2. SEM image of particles retaining surface texture reminiscent of the transient
patterns observed during solvent extraction (Fig 7b of the manuscript). Exceptional
observations attributed to particle crowding, confinement, and thus comparatively slower
phase inversion.
References
[S1] Cabral, J. T.; Hudson, S. D.; Harrison, C.; Douglas, J. F. Frontal Photopolymerization
for Microfluidic Applications. Langmuir 2004, 20, 10020-10029.
[S2] Harrison, C.; Cabral, J. T.; Stafford, C. M.; Karim, A.; Amis, E. J. A Rapid Prototyping
Technique for the Fabrication of Solvent Resistant Structures. J. Micromech. Micromach.
2004, 14, 153.
[S3] Wu, T.; Mei, Y.; Cabral, J. T.; Xu, C.; Beers, K. L. A New Synthetic Method for
Controlled Polymerization Using a Microfluidic System. J. Am. Chem. Soc. 2004, 126,
9880-9881.
[S4] Cygan, Z. T.; Cabral, J. T.; Beers, K. L.; Amis, E. J. Microfluidic Platform for the
Generation of Organic-Phase Microreactors. Langmuir 2005, 21, 3629-3634.
[S5] Cabral, J. T.; Douglas, J. F. Propagating Waves of Network Formation Induced by
Light. Polymer 2005, 46, 4230-4241.
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