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SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT3108 NATURE MATERIALS | www.nature.com/naturematerials 1 Digitally tunable physicochemical coding of material composition and topography in continuous microfibers © 2011 Macmillan Publishers Limited. All rights reserved.

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Page 1: Digitally tunable physicochemical coding of material ... · Digitally tunable physicochemical coding of material composition and topography in continuous microfibers . Supplementary

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.

Page 2: Digitally tunable physicochemical coding of material ... · Digitally tunable physicochemical coding of material composition and topography in continuous microfibers . Supplementary

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.

Page 3: Digitally tunable physicochemical coding of material ... · Digitally tunable physicochemical coding of material composition and topography in continuous microfibers . Supplementary

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.

Page 4: Digitally tunable physicochemical coding of material ... · Digitally tunable physicochemical coding of material composition and topography in continuous microfibers . Supplementary

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.

Page 5: Digitally tunable physicochemical coding of material ... · Digitally tunable physicochemical coding of material composition and topography in continuous microfibers . Supplementary

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.

Page 6: Digitally tunable physicochemical coding of material ... · Digitally tunable physicochemical coding of material composition and topography in continuous microfibers . Supplementary

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.

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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.

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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.

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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.

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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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NATURE MATERIALS | www.nature.com/naturematerials 11

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.

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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.

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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.

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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).

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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.