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 1 Toyohashi University of Technology, 2 Hamamatsu Photonics K.K. August 31, 2004, 5 th 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. Introduction 1-1. 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) Coulomb Force Taylor Cone Capillary

1-4. Microarray fabrication using CJS. Unstability of the jet.  Low accuracy of the droplet position Unstability of the jet.  Low accuracy of the droplet position Problem Coulomb Force Droplet Volume : pL ~ fL order  High-Density Microarray.

Glass Capillary 2. How to improve the unstable jet. V 1, V 2 : Simultaneously applied. V E = V 2 – V 1 : Bias Voltage 2-1. Use of capillary with an external electrode. External Electrode Insulation Area

2-2. How does the External Electrode work? Reduction of the Instability of the jet formation. Reduction of the Instability of the jet formation. Coulomb Force Additional Electric Field V E (=V 2 -V 1 ) > 0 Formation of the electric field to squeeze Taylor Cone. V E (=V 2 -V 1 ) > 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 V 1 = 600 V V E = 100 V Pulse Width : 5 ms V 1 = 600 V Pulse Width : 5 ms Capillary with the External Electrode Normal Capillary External Electrode Mirror Image 20  m

3-2. Time course of droplet formation : Digest. Capillary with External Electrode Normal Capillary Along with the axis of the capillary. Sometimes disturbed. 0 ms1 ms3 ms5 ms The Jet

3-3. Characteristics of the cone shape. CC hChC Normal Capillary 47.9° Normal Capillary 8.9  m Increase in V E    C, h C increase.

3-4. Action of V E on the Taylor Cone. V E = 0 V V E = 100 V Normal Capillary Capillary with External Electrode More squeezed with the increase in V E : Coulomb Force hChC CC

3-5. Accuracy of the droplet position.  P : Standard Deviation of  Normal Capillary 2.5  m The jet was stabilized by the squeeze of Taylor Cone. The accuracy was improved with the increase in V E. The jet was stabilized by the squeeze of Taylor Cone. The accuracy was improved with the increase in V E.

3-6. Fabrication of high-density microarray. Using Capillary with External Electrode Conventional 90  m 10  m 200  m Sample : DNA Solution (600 bp) Fluorescence Image of YOYO-1

Coulomb Force Pulse Voltage 4. More advanced application of CJS 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. Coulomb Force Initial Droplet Pulse Voltage

4-2. Microarray with gradient concentration Fluorescein (green) Rhodamine B (orange) Applicable to Combinatorial Chemistry, Drug Screening, Printing Fluorescence images from the identical microarray. 50  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. Experiment 3-1 Sample preparation. Dye solutions having High Viscosity. Fluorescein solution Rhodamine B solution Concentration1.25 x M Solvent Glycerin 95 %, Water 2.5 %, Ethanol 2.5 % Glycerin 95 %, Water 5 % Viscosity906 x Pa·s616 x Pa·s Viscosity of Water : x Pa·s.

Time course of the mixing. Capillary-1 Rhodamine B Capillary-2 Fluorescein