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SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT3108
NATURE MATERIALS | www.nature.com/naturematerials 11
Supplementary Information
Digitally tunable physicochemical coding of material composition and topography in continuous microfibers
Supplementary Text
Supplementary figure 1 to 8
Video S1 to S10 (M1 ~ M10)
© 2011 Macmillan Publishers Limited. All rights reserved.
2 NATURE MATERIALS | www.nature.com/naturematerials
SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT3108
2
Supplementary Text
Procedure for fabricating a pneumatic valve
Supplementary figure 2a shows the valve fabrication process. A through-hole (diameter: 3 mm) was punched
in the PDMS top relief at the valve position. This perforated PDMS top relief was placed on a transparent film.
The hole was covered with a droplet of PDMS pre-polymer. The pre-polymer curved parabolically under the
surface tension, and was solidified by thermal curing to form a thin membrane. The top relief, including the
parabolic membrane, was separated from the film and bonded to the bottom relief, which included rectangular
and hemi-cylindrical channels, by using oxygen plasma. The thin area of the parabolic membrane acted as a
pneumatic valve.
Analytical model for predicting the minimum thickness of the PDMS valve membrane
We assume that the pre-polymer PDMS covering the through-hole creates an appropriate radius of curvature
by the surface tension, as shown in Supplementary figure 2b. Our analytical equation is based on the principal
that the volume of the diagonal segment (Vpre) is equal to the initial volume of the pre-polymer PDMS before
physical contact (a). Referring to the diagram in Supplementary figure 2c, the volume of the diagonal segment
corresponding to the volume of pre-polymer PDMS can be obtained by subtracting the volume of the circular
segment (Vseg) from the volume of the cylinder (Vcyl).
pre cyl sega V V V (1)
Based on the geometrical features, the volumes of the circular segment and the cylinder can be expressed by
the equation
3
22 2sin cos sin3segRV
(2)
2
2cylsV h
(3)
,where θ is the contact angle of the pre-polymer PDMS on the PDMS surface, s is the diameter of the hole, R is
the radius of the curvature of the PDMS (inner valve) surface, and h is the maximum thickness of PDMS valve
corresponding to the contact line of the PDMS pre-polymer on the wall.
The radius R and height H can be expressed as follows:
2cossR
(4)
3
sec tan2sh x
(5)
, where x is the minimum thickness of the PDMS valve.
Thus, the initial volume (a) can be expressed as a function of the minimum thickness (x), contact angle (θ),
and diameter of the hole (s) by substituting Eq. (2), (3), (4), and (5) into Eq. (1) as follows;
2
3 36 3 sec 2 sec 2 tan24sa x s s s
(6)
Finally, the minimum thickness of the PDMS valve membrane, x, can be defined as
3 32
1 24 3 sec 2 sec 2 tan6
ax s s ss
(7)
, where the liquid PDMS contact angle, θ, measured in the PDMS well, was found to be ~15° and the diameter of
the hole, s, is constant in our system. Therefore the thickness of the membrane is determined only by the volume
of the PDMS pre-polymer. Supplementary figure 3 (a-left) shows the simulation results of the minimum PDMS
valve thickness, and this model was analyzed using computational fluid dynamics tools (COMSOL, MA), and
the two-dimensional axis-symmetric model was used with the surface tensions of the liquid PDMS-air interfaces
set to 0.019 N/m, respectively.1 Supplementary figure 3 (a-right) shows that the valve membrane thickness
increased for increasing volume of the deposited prepolymer. Supplementary figure 3b shows a plot of the
theoretical and experimental membrane thickness, demonstrating that the analytical model successfully predicted
the membrane thickness. Supplementary figure 3c shows a SEM image of the cross-sectional view of the
parabolic membrane in the valve.
Relationship between concentration of Ca2+ ions and fiber generation
Ca2+ ions were introduced by the aqueous sheath fluid (0.1 g ~ 0.4 g calcium chlorides dissolved in 10 mL DI
water), which surrounded and focused towards alginate flow along a channel. As the Ca2+ ions in sheath fluid
diffused into the alginate stream they induced crosslinking of the alginate to generate a fiber. Also, sheath flow
including Ca2+ ions acted as a lubricant. Alginate crosslinking time was regulated by the concentration of Ca2+
ions, which also played a pivotal role in controlling the rigidity of alginate fibers.2 When we encoded various
morphologies such as grooves and tapered shapes into the fiber, we adopted a relatively high concentration of
Ca2+ ions (0.3~0.4 g/mL water). When we encoded chemicals and cells in the fibers, we employed a lower
concentration of Ca2+ ions (0.1g/10mL water).
Fabrication of grooved fibers
To fabricate grooved fibers, inner-patterned PDMS cylindrical channels were fabricated. The detail process is
© 2011 Macmillan Publishers Limited. All rights reserved.
NATURE MATERIALS | www.nature.com/naturematerials 3
SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT3108
2
Supplementary Text
Procedure for fabricating a pneumatic valve
Supplementary figure 2a shows the valve fabrication process. A through-hole (diameter: 3 mm) was punched
in the PDMS top relief at the valve position. This perforated PDMS top relief was placed on a transparent film.
The hole was covered with a droplet of PDMS pre-polymer. The pre-polymer curved parabolically under the
surface tension, and was solidified by thermal curing to form a thin membrane. The top relief, including the
parabolic membrane, was separated from the film and bonded to the bottom relief, which included rectangular
and hemi-cylindrical channels, by using oxygen plasma. The thin area of the parabolic membrane acted as a
pneumatic valve.
Analytical model for predicting the minimum thickness of the PDMS valve membrane
We assume that the pre-polymer PDMS covering the through-hole creates an appropriate radius of curvature
by the surface tension, as shown in Supplementary figure 2b. Our analytical equation is based on the principal
that the volume of the diagonal segment (Vpre) is equal to the initial volume of the pre-polymer PDMS before
physical contact (a). Referring to the diagram in Supplementary figure 2c, the volume of the diagonal segment
corresponding to the volume of pre-polymer PDMS can be obtained by subtracting the volume of the circular
segment (Vseg) from the volume of the cylinder (Vcyl).
pre cyl sega V V V (1)
Based on the geometrical features, the volumes of the circular segment and the cylinder can be expressed by
the equation
3
22 2sin cos sin3segRV
(2)
2
2cylsV h
(3)
,where θ is the contact angle of the pre-polymer PDMS on the PDMS surface, s is the diameter of the hole, R is
the radius of the curvature of the PDMS (inner valve) surface, and h is the maximum thickness of PDMS valve
corresponding to the contact line of the PDMS pre-polymer on the wall.
The radius R and height H can be expressed as follows:
2cossR
(4)
3
sec tan2sh x
(5)
, where x is the minimum thickness of the PDMS valve.
Thus, the initial volume (a) can be expressed as a function of the minimum thickness (x), contact angle (θ),
and diameter of the hole (s) by substituting Eq. (2), (3), (4), and (5) into Eq. (1) as follows;
2
3 36 3 sec 2 sec 2 tan24sa x s s s
(6)
Finally, the minimum thickness of the PDMS valve membrane, x, can be defined as
3 32
1 24 3 sec 2 sec 2 tan6
ax s s ss
(7)
, where the liquid PDMS contact angle, θ, measured in the PDMS well, was found to be ~15° and the diameter of
the hole, s, is constant in our system. Therefore the thickness of the membrane is determined only by the volume
of the PDMS pre-polymer. Supplementary figure 3 (a-left) shows the simulation results of the minimum PDMS
valve thickness, and this model was analyzed using computational fluid dynamics tools (COMSOL, MA), and
the two-dimensional axis-symmetric model was used with the surface tensions of the liquid PDMS-air interfaces
set to 0.019 N/m, respectively.1 Supplementary figure 3 (a-right) shows that the valve membrane thickness
increased for increasing volume of the deposited prepolymer. Supplementary figure 3b shows a plot of the
theoretical and experimental membrane thickness, demonstrating that the analytical model successfully predicted
the membrane thickness. Supplementary figure 3c shows a SEM image of the cross-sectional view of the
parabolic membrane in the valve.
Relationship between concentration of Ca2+ ions and fiber generation
Ca2+ ions were introduced by the aqueous sheath fluid (0.1 g ~ 0.4 g calcium chlorides dissolved in 10 mL DI
water), which surrounded and focused towards alginate flow along a channel. As the Ca2+ ions in sheath fluid
diffused into the alginate stream they induced crosslinking of the alginate to generate a fiber. Also, sheath flow
including Ca2+ ions acted as a lubricant. Alginate crosslinking time was regulated by the concentration of Ca2+
ions, which also played a pivotal role in controlling the rigidity of alginate fibers.2 When we encoded various
morphologies such as grooves and tapered shapes into the fiber, we adopted a relatively high concentration of
Ca2+ ions (0.3~0.4 g/mL water). When we encoded chemicals and cells in the fibers, we employed a lower
concentration of Ca2+ ions (0.1g/10mL water).
Fabrication of grooved fibers
To fabricate grooved fibers, inner-patterned PDMS cylindrical channels were fabricated. The detail process is
© 2011 Macmillan Publishers Limited. All rights reserved.
4 NATURE MATERIALS | www.nature.com/naturematerials
SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT3108
4
described in Supplementary figure 6a: (1) Micro groove patterns (Photoresistor: AZ 1512) were constructed on
the silicon wafer using photolithography processes (Supplementary figure 6 (a-i)). (2) On top of the patterned
mold, a thin PDMS film was spin-coated, and the replicated PDMS membrane was fabricated (Supplementary
figure 6 (a-ii)). (3) The PDMS base mold, including degassing port, was affixed onto the patterned membrane by
plasma bonding (Supplementary figure 6 (a-iii)). (4) The membrane was separated from the wafer to form a
concave hemicylindrical channel structure upon application of negative pressure (Supplementary figure 6 (a-iv)).
(5) The hemicylindrical shape of the deformed membrane was replicated using SU-8 followed by UV curing.
Then, a convex hemicylindrical SU-8 master mold was completed (Supplementary figure 6 (a-v)). (6) A convex
hemicylindrical SU-8 master mold was replicated using PDMS; then, the hemicylindrical concave grooved
PDMS channel was fabricated. (7) By aligning and bonding two hemicylindrical concave grooved PDMS
channels via oxygen plasma treatment, the grooved channels were constructed (Supplementary figure 6(a-vii)).
The groove-patterned fibers can be produced using the grooved channel. Various patterns can be made on the
fiber by changing the groove pattern as shown in Supplementary figure 6b.To fabricate the grooved fibers, a 4
wt%(0.4 g/mL water) alginate solution was used to reduce the polymerization time of the alginate solution.
Generation of bubble encoded fibers
Air was injected into a sample inlet channel at a pressure of 10–50 kPa and a 3 wt% alginate solution mixed
with a 1% surfactant solution was injected into another inlet. The surfactant prevented aggregation of bubbles
and the uniformly distributed bubbles were embedded in the fiber. By controlling the ‘on–off’ sequence of valve
integrating with bubble channel, air bubbles were embedded into the alginate fiber. The flow rates of the
alginate solution and CaCl2 solution were 20–50 L/min and 20–40 mL/h, respectively.
Spatiotemporal coding of different chemical compositions in the fiber
To fabricate a fiber encoded with different material compositions, three channels were used. By controlling
the ‘on–off’ sequence of various channels, fibers were produced according to the digital coding scheme. In
achieving serial coding, two or three sample channels were opened sequentially, with a typical opening time
(‘open’ signal) of 0.05 sec. Serial coding length was reduced to less than 1mm when the minimum opening time
was set below 0.1 sec (Supplementary figure 7). Similarly, the embossed and serially encoded fibers were
fabricated by delaying the infusing samples and overlapping the ‘open’ signals by ~0.1 sec. The mixed serial
and parallel encoded fibers were fabricated by using the serial coding signal with the addition of a period of
open signals for all samples thereafter. For better visualization, we used red, green, and blue fluorescent
polystyrene microspheres (300 nm size PS bead, Thermo), which were mixed with the alginate solution to a
concentration of 0.05% wt/vol.
Primary Hepatocyte Isolation
Cells were isolated from 7 weeks male SD rats (250 – 300g) using a standard two-step collagenase perfusion
5
procedure. Details of isolation have been described previously.3 Isolated cell suspensions were separated by
centrifuge at 50g for 1min, twice. The pellet was suspended in L-15 medium (Invitrogen) supplemented with
20mM HEPES, 1.1g/l galactose, 30mg/l proline, 0.5mg/l insulin, 10-7M dexamethasone, and
Penicillin/streptomycin. The pellet was re-suspended in L-15 medium and percoll solution (95% Percoll solution
in HBSS) in a ratio of 1:1 and centrifuged again at 50g for 15min. This step is used to separate live cells and
dead cells in different layers. Thereafter, the upper solution was removed and the pellet was re-suspended in L-
15 medium and centrifuged 50g for 1min again, to remove any remaining percoll solution. Finally, the pellet
was suspended in DMEM of high glucose content supplemented with 20mM HEPES, 25mM NaHCO3, 30mg/l
L-Proline, 0.5mg/l insulin, 10-7M dexamethasone, 10% FBS, 10mM nicotinamide, 1mM ascorbic acid-
phosphate, 10ng/l EGF, and penicillin/streptomycin.
Isolation of primary rat neural cells
Rat embryonic cortical neurons were obtained as described previously.4 Briefly, one embryo per preparation
was recovered from pregnant SD-rats at 16 days gestation. Cortices were removed from the occipital cortex of
both hemispheres in cold hank’s balanced salt solution (HBSS) using micro scissors. After dissection, cells were
mechanically dissociated by Tryp LE in 3 ml HBSS (without calcium and magnesium) for 15 min, and then they
were washed with HBSS (with calcium and magnesium) for two times. Non-dispersed tissues were allowed to
settle and the supernatant was filtered (70 m nylon filter). After staining filtered cell with trypan blue, live cells
were analyzed and counted. Cells were cultured with neurobasal medium supplemented B27, 200mM L-
Glutamine and 10ng/ml NGF (All solutions were purchased from Invitrogen). Culture medium was changed
every 2 days.
Preparation of Neutrophil
Human promyelocytic HL-60 cells were obtained from Korean Cell Line Bank (KCLB, South Korea) and
grown in RPMI-1640 medium (Thermo Scientific, USA) supplemented with 10% fetal bovine serum, 0.1mM
nonessential amino acids, 50 U/ml penicillin and 50 μg/ml streptomycin incubated at 37°C, humidified 5% CO2
environment. Aliquots of HL-60 cell suspension (5×105 cells/ml) were seeded onto tissue culture flasks and were
grown for 5 days in the presence of 1.25% DMSO. We observed that promyelocytes were differentiated and then
confirmed whether differentiation to neutrophil occurred by using the following four conditions: 1) Cell
morphology 2) Cell proliferation assay with 0.4% trypan blue exclusion 3) Surface expression of differentiation-
related Ags evaluated by flow cytometry using FITC-conjugated monoclonal antibodies against CD11b, CD16
and CD33. 4) Myeloid cell maturation was determined by spectrophotometer at 540 nm. Cells were stained by
Vybrant® CFDA SE Cell Tracer (invitrogen) with concentration of 2.5 M.
© 2011 Macmillan Publishers Limited. All rights reserved.
NATURE MATERIALS | www.nature.com/naturematerials 5
SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT3108
4
described in Supplementary figure 6a: (1) Micro groove patterns (Photoresistor: AZ 1512) were constructed on
the silicon wafer using photolithography processes (Supplementary figure 6 (a-i)). (2) On top of the patterned
mold, a thin PDMS film was spin-coated, and the replicated PDMS membrane was fabricated (Supplementary
figure 6 (a-ii)). (3) The PDMS base mold, including degassing port, was affixed onto the patterned membrane by
plasma bonding (Supplementary figure 6 (a-iii)). (4) The membrane was separated from the wafer to form a
concave hemicylindrical channel structure upon application of negative pressure (Supplementary figure 6 (a-iv)).
(5) The hemicylindrical shape of the deformed membrane was replicated using SU-8 followed by UV curing.
Then, a convex hemicylindrical SU-8 master mold was completed (Supplementary figure 6 (a-v)). (6) A convex
hemicylindrical SU-8 master mold was replicated using PDMS; then, the hemicylindrical concave grooved
PDMS channel was fabricated. (7) By aligning and bonding two hemicylindrical concave grooved PDMS
channels via oxygen plasma treatment, the grooved channels were constructed (Supplementary figure 6(a-vii)).
The groove-patterned fibers can be produced using the grooved channel. Various patterns can be made on the
fiber by changing the groove pattern as shown in Supplementary figure 6b.To fabricate the grooved fibers, a 4
wt%(0.4 g/mL water) alginate solution was used to reduce the polymerization time of the alginate solution.
Generation of bubble encoded fibers
Air was injected into a sample inlet channel at a pressure of 10–50 kPa and a 3 wt% alginate solution mixed
with a 1% surfactant solution was injected into another inlet. The surfactant prevented aggregation of bubbles
and the uniformly distributed bubbles were embedded in the fiber. By controlling the ‘on–off’ sequence of valve
integrating with bubble channel, air bubbles were embedded into the alginate fiber. The flow rates of the
alginate solution and CaCl2 solution were 20–50 L/min and 20–40 mL/h, respectively.
Spatiotemporal coding of different chemical compositions in the fiber
To fabricate a fiber encoded with different material compositions, three channels were used. By controlling
the ‘on–off’ sequence of various channels, fibers were produced according to the digital coding scheme. In
achieving serial coding, two or three sample channels were opened sequentially, with a typical opening time
(‘open’ signal) of 0.05 sec. Serial coding length was reduced to less than 1mm when the minimum opening time
was set below 0.1 sec (Supplementary figure 7). Similarly, the embossed and serially encoded fibers were
fabricated by delaying the infusing samples and overlapping the ‘open’ signals by ~0.1 sec. The mixed serial
and parallel encoded fibers were fabricated by using the serial coding signal with the addition of a period of
open signals for all samples thereafter. For better visualization, we used red, green, and blue fluorescent
polystyrene microspheres (300 nm size PS bead, Thermo), which were mixed with the alginate solution to a
concentration of 0.05% wt/vol.
Primary Hepatocyte Isolation
Cells were isolated from 7 weeks male SD rats (250 – 300g) using a standard two-step collagenase perfusion
5
procedure. Details of isolation have been described previously.3 Isolated cell suspensions were separated by
centrifuge at 50g for 1min, twice. The pellet was suspended in L-15 medium (Invitrogen) supplemented with
20mM HEPES, 1.1g/l galactose, 30mg/l proline, 0.5mg/l insulin, 10-7M dexamethasone, and
Penicillin/streptomycin. The pellet was re-suspended in L-15 medium and percoll solution (95% Percoll solution
in HBSS) in a ratio of 1:1 and centrifuged again at 50g for 15min. This step is used to separate live cells and
dead cells in different layers. Thereafter, the upper solution was removed and the pellet was re-suspended in L-
15 medium and centrifuged 50g for 1min again, to remove any remaining percoll solution. Finally, the pellet
was suspended in DMEM of high glucose content supplemented with 20mM HEPES, 25mM NaHCO3, 30mg/l
L-Proline, 0.5mg/l insulin, 10-7M dexamethasone, 10% FBS, 10mM nicotinamide, 1mM ascorbic acid-
phosphate, 10ng/l EGF, and penicillin/streptomycin.
Isolation of primary rat neural cells
Rat embryonic cortical neurons were obtained as described previously.4 Briefly, one embryo per preparation
was recovered from pregnant SD-rats at 16 days gestation. Cortices were removed from the occipital cortex of
both hemispheres in cold hank’s balanced salt solution (HBSS) using micro scissors. After dissection, cells were
mechanically dissociated by Tryp LE in 3 ml HBSS (without calcium and magnesium) for 15 min, and then they
were washed with HBSS (with calcium and magnesium) for two times. Non-dispersed tissues were allowed to
settle and the supernatant was filtered (70 m nylon filter). After staining filtered cell with trypan blue, live cells
were analyzed and counted. Cells were cultured with neurobasal medium supplemented B27, 200mM L-
Glutamine and 10ng/ml NGF (All solutions were purchased from Invitrogen). Culture medium was changed
every 2 days.
Preparation of Neutrophil
Human promyelocytic HL-60 cells were obtained from Korean Cell Line Bank (KCLB, South Korea) and
grown in RPMI-1640 medium (Thermo Scientific, USA) supplemented with 10% fetal bovine serum, 0.1mM
nonessential amino acids, 50 U/ml penicillin and 50 μg/ml streptomycin incubated at 37°C, humidified 5% CO2
environment. Aliquots of HL-60 cell suspension (5×105 cells/ml) were seeded onto tissue culture flasks and were
grown for 5 days in the presence of 1.25% DMSO. We observed that promyelocytes were differentiated and then
confirmed whether differentiation to neutrophil occurred by using the following four conditions: 1) Cell
morphology 2) Cell proliferation assay with 0.4% trypan blue exclusion 3) Surface expression of differentiation-
related Ags evaluated by flow cytometry using FITC-conjugated monoclonal antibodies against CD11b, CD16
and CD33. 4) Myeloid cell maturation was determined by spectrophotometer at 540 nm. Cells were stained by
Vybrant® CFDA SE Cell Tracer (invitrogen) with concentration of 2.5 M.
© 2011 Macmillan Publishers Limited. All rights reserved.
6 NATURE MATERIALS | www.nature.com/naturematerials
SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT3108
6
References
1 Berthier, J. Microdrops and digital microfluidics. (William Andrew Pub., 2008).
2 Mancini, M., Moresi, M. & Rancini, R. Mechanical properties of alginate gels: empirical
characterisation. J Food Eng 39, 369-378 (1999).
3 Dunn, J. C. Y., Yarmush, M. L., Koebe, H. G. & Tompkins, R. G. Hepatocyte Function and
Extracellular-Matrix Geometry - Long-Term Culture in a Sandwich Configuration. Faseb J 3, 174-177
(1989).
4 Huettner, J. E. & Baughman, R. W. Primary Culture of Identified Neurons from the Visual-Cortex of
Postnatal Rats. J Neurosci 6, 3044-3060 (1986).
7
Supplementary figures
Supplementary figure 1 Schematic diagram of the valve control.
© 2011 Macmillan Publishers Limited. All rights reserved.
NATURE MATERIALS | www.nature.com/naturematerials 7
SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT3108
6
References
1 Berthier, J. Microdrops and digital microfluidics. (William Andrew Pub., 2008).
2 Mancini, M., Moresi, M. & Rancini, R. Mechanical properties of alginate gels: empirical
characterisation. J Food Eng 39, 369-378 (1999).
3 Dunn, J. C. Y., Yarmush, M. L., Koebe, H. G. & Tompkins, R. G. Hepatocyte Function and
Extracellular-Matrix Geometry - Long-Term Culture in a Sandwich Configuration. Faseb J 3, 174-177
(1989).
4 Huettner, J. E. & Baughman, R. W. Primary Culture of Identified Neurons from the Visual-Cortex of
Postnatal Rats. J Neurosci 6, 3044-3060 (1986).
7
Supplementary figures
Supplementary figure 1 Schematic diagram of the valve control.
© 2011 Macmillan Publishers Limited. All rights reserved.
8 NATURE MATERIALS | www.nature.com/naturematerials
SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT3108
8
Supplementary figure 2 (a) The procedure for fabricating a pneumatic valve by dropping a small PDMS
prepolymer droplet onto the opening of a perforated hole; (b) Geometries used in the calculation of the
minimum thickness x; (c) volumetric geometries used in the Eq. (1-7)
9
Supplementary figure 3 (a) An analytical model for membrane formation; the model was used to determine the
film thickness formed by a PDMS prepolymer droplet (left), cross-sectional view of valves for various
prepolymer volumes (right); (b) experimental and theoretical thickness of the membrane. Data are expressed as
mean ± s.d. (n ≥ 10); (c) SEM image of the parabolic membrane. The scale bars indicate 1mm in a, and 200m
in c.
© 2011 Macmillan Publishers Limited. All rights reserved.
NATURE MATERIALS | www.nature.com/naturematerials 9
SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT3108
8
Supplementary figure 2 (a) The procedure for fabricating a pneumatic valve by dropping a small PDMS
prepolymer droplet onto the opening of a perforated hole; (b) Geometries used in the calculation of the
minimum thickness x; (c) volumetric geometries used in the Eq. (1-7)
9
Supplementary figure 3 (a) An analytical model for membrane formation; the model was used to determine the
film thickness formed by a PDMS prepolymer droplet (left), cross-sectional view of valves for various
prepolymer volumes (right); (b) experimental and theoretical thickness of the membrane. Data are expressed as
mean ± s.d. (n ≥ 10); (c) SEM image of the parabolic membrane. The scale bars indicate 1mm in a, and 200m
in c.
© 2011 Macmillan Publishers Limited. All rights reserved.
10 NATURE MATERIALS | www.nature.com/naturematerials
SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT3108
10
Supplementary figure 4 (a) Schematic diagram of the spinning ducts; (b) SEM image of the end of the chip;
the structural cross-section is cylindrical; (c) winding system of extruded fiber with electrical motor (the inset
shows the wound fibers on the spool) (see Video S2 file); (d) Graph of the relationship between the maximum
winding velocity and sheath flow rates (Sample flow rate: 0.6 ml/h). Data are expressed as mean ± s.d. (n ≥ 5);
the scale bars indicate 300m in c, 200m in (c, inset)
11
Supplementary figure 5 (a) SEM image of dried alginate fibers (inset: SEM image of dried fibers as a function
of pressure applied to the pneumatic valve); (b) Diameter of the wet alginate fibers as a function of the pressure
applied to the alginate solution (by water column) and pneumatic valves. Data are expressed as mean ± s.d (n ≥
20). The scale bar indicate 40m in a, 20m in (a, inset)
© 2011 Macmillan Publishers Limited. All rights reserved.
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SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT3108
10
Supplementary figure 4 (a) Schematic diagram of the spinning ducts; (b) SEM image of the end of the chip;
the structural cross-section is cylindrical; (c) winding system of extruded fiber with electrical motor (the inset
shows the wound fibers on the spool) (see Video S2 file); (d) Graph of the relationship between the maximum
winding velocity and sheath flow rates (Sample flow rate: 0.6 ml/h). Data are expressed as mean ± s.d. (n ≥ 5);
the scale bars indicate 300m in c, 200m in (c, inset)
11
Supplementary figure 5 (a) SEM image of dried alginate fibers (inset: SEM image of dried fibers as a function
of pressure applied to the pneumatic valve); (b) Diameter of the wet alginate fibers as a function of the pressure
applied to the alginate solution (by water column) and pneumatic valves. Data are expressed as mean ± s.d (n ≥
20). The scale bar indicate 40m in a, 20m in (a, inset)
© 2011 Macmillan Publishers Limited. All rights reserved.
12 NATURE MATERIALS | www.nature.com/naturematerials
SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT3108
12
Supplementary figure 6 (a) Schematic diagram of the fabrication process of grooved microchannels; Basic
fabrication process of the SU-8 master mold used to produce patterned cylindrical channels using a thin PDMS
patterned membrane. (b) Top view and 3D schematics of groove coding on the fiber surface using a grooved
round channel.
13
Supplementary figure 7 (a) Fluorescent image of serially encoded fiber with minimum coding length. The
border region between coded areas was somewhat distorted indicating that there may also be issues with fluid
mixing and laminar profiles related to making extremely small regions. (b) The relationship between the valve
opening time (time sequence) and serial coding length. Data are expressed as mean ± s.d (n ≥ 20) (Flow rate of
sample fluid: 10l/min and sheath fluid: 20 ml/h). The scale bars indicate 1000 m in a.
© 2011 Macmillan Publishers Limited. All rights reserved.
NATURE MATERIALS | www.nature.com/naturematerials 13
SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT3108
12
Supplementary figure 6 (a) Schematic diagram of the fabrication process of grooved microchannels; Basic
fabrication process of the SU-8 master mold used to produce patterned cylindrical channels using a thin PDMS
patterned membrane. (b) Top view and 3D schematics of groove coding on the fiber surface using a grooved
round channel.
13
Supplementary figure 7 (a) Fluorescent image of serially encoded fiber with minimum coding length. The
border region between coded areas was somewhat distorted indicating that there may also be issues with fluid
mixing and laminar profiles related to making extremely small regions. (b) The relationship between the valve
opening time (time sequence) and serial coding length. Data are expressed as mean ± s.d (n ≥ 20) (Flow rate of
sample fluid: 10l/min and sheath fluid: 20 ml/h). The scale bars indicate 1000 m in a.
© 2011 Macmillan Publishers Limited. All rights reserved.
14 NATURE MATERIALS | www.nature.com/naturematerials
SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT3108
14
Supplementary figure 8 Confocal image of mixture region stained cells embedded at the different depth of
fiber. The scale bar indicates 100m. Plots of fluorescence intensity are drawn against displacement across
different levels (Z) of the fibers.
15
Legends of Videos
Video S1: shows real-time cutting of alginate fiber making use of two channels on a fiber spinning chip. PBS
and alginate solutions were alternately introduced into each sample channel and the length of fiber was
controlled by changing the opening time of each valve.
Video S2: shows the winding system of extruded fiber. The fiber was successfully twined on the spool by
controlling the motor speed which is in coordination with the extruding speed of fiber.
Video S3: shows fabrication of embossed fiber with the use of two channels on a fiber spinning chip. Same
alginate solution was introduced into each sample channel and the diameter and sequence of fiber were
controlled by changing the flow rates of samples and opening time of each valve.
Video S4: shows fabrication of tapered fiber implementing two channels on a fiber spinning chip. The same
alginate solution was injected into each channel but the open and close sequence of the valves were different. By
imposing the delay function of LAB-VIEW programming, the total volume was changed gradually to fabricate a
tapered fiber.
Video S5: shows the real-time encapsulation of bubbles into a fiber. Air was injected into one inlet channel at a
pressure of 10–50 kPa. The other inlet channel contained a 2 wt% alginate solution mixed with a 1% surfactant
solution.
Video S6: shows a confocal microscopic image of twisted fiber comprising of red, green and blue fluorescently-
dyed fibers.
Video S7: shows the real-time fabrication of a single fiber containing serially coded regions. Three sample
channels were opened in an arranged order with an opening time (‘open’ signal) of 0.3 sec.
Video S8: shows the fabrication of embossed and serially encoded fibers fabricated by delaying the sample
infusion and overlapping the ‘open’ signals by approximately 0.1 sec.
Video S9: shows the real-time fabrication of fibers that contained serially coded regions. Two inlet channels
were opened in arranged order. The valve opening times (‘open’ signal) ranged from 0.05 sec to 0.5 sec.
Video S10: shows the neutrophil migration to the encoded fMLP encoded region. Total recorded time was 6
hours (green: neutrophil, red: fMLP).
© 2011 Macmillan Publishers Limited. All rights reserved.
NATURE MATERIALS | www.nature.com/naturematerials 15
SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT3108
14
Supplementary figure 8 Confocal image of mixture region stained cells embedded at the different depth of
fiber. The scale bar indicates 100m. Plots of fluorescence intensity are drawn against displacement across
different levels (Z) of the fibers.
15
Legends of Videos
Video S1: shows real-time cutting of alginate fiber making use of two channels on a fiber spinning chip. PBS
and alginate solutions were alternately introduced into each sample channel and the length of fiber was
controlled by changing the opening time of each valve.
Video S2: shows the winding system of extruded fiber. The fiber was successfully twined on the spool by
controlling the motor speed which is in coordination with the extruding speed of fiber.
Video S3: shows fabrication of embossed fiber with the use of two channels on a fiber spinning chip. Same
alginate solution was introduced into each sample channel and the diameter and sequence of fiber were
controlled by changing the flow rates of samples and opening time of each valve.
Video S4: shows fabrication of tapered fiber implementing two channels on a fiber spinning chip. The same
alginate solution was injected into each channel but the open and close sequence of the valves were different. By
imposing the delay function of LAB-VIEW programming, the total volume was changed gradually to fabricate a
tapered fiber.
Video S5: shows the real-time encapsulation of bubbles into a fiber. Air was injected into one inlet channel at a
pressure of 10–50 kPa. The other inlet channel contained a 2 wt% alginate solution mixed with a 1% surfactant
solution.
Video S6: shows a confocal microscopic image of twisted fiber comprising of red, green and blue fluorescently-
dyed fibers.
Video S7: shows the real-time fabrication of a single fiber containing serially coded regions. Three sample
channels were opened in an arranged order with an opening time (‘open’ signal) of 0.3 sec.
Video S8: shows the fabrication of embossed and serially encoded fibers fabricated by delaying the sample
infusion and overlapping the ‘open’ signals by approximately 0.1 sec.
Video S9: shows the real-time fabrication of fibers that contained serially coded regions. Two inlet channels
were opened in arranged order. The valve opening times (‘open’ signal) ranged from 0.05 sec to 0.5 sec.
Video S10: shows the neutrophil migration to the encoded fMLP encoded region. Total recorded time was 6
hours (green: neutrophil, red: fMLP).
© 2011 Macmillan Publishers Limited. All rights reserved.