Properties of Droplet Formation made by Cone Jet

using a Novel Capillary with an External Electrode

Osamu Yogi 1,2, Tomonori Kawakami 2, and Akira Mizuno 1

1Toyohashi University of Technology, 2Hamamatsu Photonics K.K.

August 31, 2004, 　 5th EHD International Workshop (Poitiers, France)

Agenda

• 1. Introduction.– Droplet formation using Cone-Jet Mode

• 2. How to improve the Instabilty.– Use of the capillary with an external electrode.

• 3. Experiments.– Properties of the cone shape– Accuracy of the droplet position.

• 4. More advanced Application of Cone-Jet Spotting.

• 5. Conclusion

1. Introduction1-1. Microarray required in analytical chemistry.

Yeast Genome Chip.

P. O. Brown Lab.,Stanford University.

Pen Type Inkjet Type

•On-Demand Droplet Spotting.•High-Sensitive Photo Detection.•On-Demand Droplet Spotting.•High-Sensitive Photo Detection.

Key Technology

1-2. What does microarray analysis need?

Spatial Resolution of Optical

Measurement.~m order

Mismatch

Distance between Spots.

~200 m

Fabricating High-Density Microarray.

Improving the Throughput.

Fabricating High-Density Microarray.

Improving the Throughput.

• Features– Thin jet from the cone.

Extremely Small Droplet

1-3. Droplet formation using Cone-Jet Mode.

Cone-Jet Spotting(CJS)

Cone-Jet Spotting(CJS)

CoulombForce

TaylorCone

Capillary

1-4. Microarray fabrication using CJS.

Unstability of the jet .

Low accuracy of the droplet positionUnstability of the jet .

Low accuracy of the droplet positionProblem

Coulomb Force

Droplet Volume : pL ~ fL order High-Density Microarray.

Glass Capillary

2. How to improve the unstable jet.

V1, V2 : Simultaneously applied.

VE = V2 – V1 : Bias Voltage

2-1. Use of capillary with an external electrode.

ExternalElectrode

InsulationArea

2-2. How does the External Electrode work?

Reduction of the Instability of the jet formation.

Reduction of the Instability of the jet formation.

CoulombForce

AdditionalElectric

Field

VE (=V2-V1) > 0

Formation of the electric field

to squeeze Taylor Cone.

VE (=V2-V1) > 0

Formation of the electric field

to squeeze Taylor Cone.

3. Experiments

3-1. Time course of droplet formation.Sample : Deionized Water, Substrate : Quartz with ITO Layer

V1 = 600 VVE = 100 V

Pulse Width: 5 ms

V1 = 600 V

Pulse Width: 5 ms

Capillary withthe External

ElectrodeNormal Capillary

ExternalElectrode

MirrorImage

20 m 20 m

3-2. Time course of droplet formation : Digest.

Capillary with External Electrode

Normal Capillary

Along with the axis of the capillary.

Along with the axis of the capillary.

Sometimes disturbed.Sometimes disturbed.

0 ms 1 ms 3 ms 5 ms The Jet

3-3. Characteristics of the cone shape.

C

hC

Normal Capillary47.9°

Normal Capillary8.9 m

Increase in VEC, hC increase.Increase in VEC, hC increase.

3-4. Action of VE on the Taylor Cone.

VE = 0 V VE = 100 V

NormalCapillary

Capillary withExternal Electrode

More squeezed with the increase in VEMore squeezed with the increase in VE: Coulomb Force

hC

C

3-5. Accuracy of the droplet position.

P : Standard Deviation of

NormalCapillary2.5 m

The jet was stabilized by the squeeze of Taylor Cone.

The accuracy was improved with the increase in VE.

The jet was stabilized by the squeeze of Taylor Cone.

The accuracy was improved with the increase in VE.

3-6. Fabrication of high-density microarray.

Using Capillary withExternal Electrode

Conventional

90 m

90

m

10

m

200

m

Sample : DNA Solution (600 bp)Fluorescence Image of YOYO-1

CoulombForce

Pulse Voltage

4. More advanced application of CJS.

4-1. Mixing inside a single droplet on a substrate.

Mixing ratio is controllable by adjusting the pulse width and height.

Mixing ratio is controllable by adjusting the pulse width and height.

CoulombForce

InitialDroplet

Pulse Voltage

4-2. Microarray with gradient concentration

Fluorescein (green) Rhodamine B (orange)

Applicable toApplicable toCombinatorial Chemistry,Drug Screening, Printing

Fluorescence images from the identical microarray.

50 m50 m

5. Conclusion

• Use of the capillary with the external electrode, Taylor Cone was squeezed. The jet was stabilized.

• Accuracy of the droplet position.

2.5 m (normal capillary) 1.1 m.in Standard

Deviation

• Great contribution to applications of Cone-Jet Spotting.

3. Experiment3-1 Sample preparation.• Dye solutions having High Viscosity.

Fluorescein solution

Rhodamine B solution

Concentration 1.25 x 10-4 M 1.25 x 10-4 M

SolventGlycerin 95 %,

Water 2.5 %,Ethanol 2.5 %

Glycerin 95 %,Water 5 %

Viscosity 906 x 10-3 Pa·s 616 x 10-3 Pa·s

Viscosity of Water : 1.002 x 10-3 Pa·s.

Time course of the mixing.

ms

5.15.10

0.80.85.1

0.170.85.1

V 5501

V

ms

5.15.10

0.80.85.1

0.170.85.1

V 5501

V

ms

252529

151525

01525

V 5702

V

Capillary-1Rhodamine B

Capillary-2Fluorescein