PicoFill-Systems Outlicensing Electrospray Deposition onto Small Targets

1. PicoFill-SystemsOutlicensing Electrospray Deposition onto Small Targets • Technology Platform Requirements: • High Voltage power supply (2 kV) to induce an electric field between a capillary-outlet and a substrate. • Liquid flow through a capillary induced by a pump or induced by pressure (preferably stable liquid flow for precision spraying). The Harvard 2000 allows liquid flows down to a few picoliters/second. • Computer controlled x-y-(z) stage (preferably high speed- and micrometer-precision actuators). • Microscope–CCDcamera set-up to visualize and verify proper spraying. • Low–high conductive surfaces: silicon nitride, metal, metal coated plastics (10 nm thick metal layer) • Liquid surface tension < 0.05 N/m: pure water requires addition of > 0.1% of the surfactant Brij 35. • Capillary material: any low–high conductive material.

2. Spraying Set-Up Example: assembled devices Syringe-capillary Harvard Pump High Precision Microscope, CCD-camera Computer controlled Motion controller: Sends x-y-z data to the x-y-z table Syringe-capillary Power Supply x-y-z stage MicroArray Upon execution of the desired x-y-z data, a substrate is moved underneath a capillary at high precision while liquid is sprayed onto the substrate at controlled flow rates of picoliters–nanoliters per second.

3. Spraying of Arrays of Dots A. Piston pushes liquid through syringe while electric field is applied C. Slide is moved upward and spraying resumes B. Slide is moved downward to lower the electric field: spraying stops 1-2 kV 1–2 kV 1-2 kV Spray of droplets Second spot is sprayed onto slide MicroArray or slide Spot Slide is moved downward and sideways: typical 200 – 1000 micron

4. Spraying Parameters Dot Size • Dot size is related to the distance between the capillary-tip and the substrate (spraying distance) • Dot size is related to the capillary outer diameter: the smaller the outer diameter, the smaller the cone size • Dot size is related to the flow rate: at low flow rates the liquid evaporates rapidly resulting in a solid dot instead of a donut like dot. • Typical dot sizes for a capillary-OD of 150 micron and flow rates of 100–400 picoliter/second : 150–400 microns at spraying distances of 250–500 micron, respectively MicroArray Applications • Flow rates: picoliters-nanoliters/second • Distance between capillary-tip and substrate (spraying distance): 200–500 micron • Dot size microarray: 100–400 micron at spraying distances of 200–500 micron • Preferred capillary outer diameter: 50–200 micron • Maximum speed of x-y-z table depends on actuators: 1.6 inch/sec (4 cm/s) for high speed actuators Dotting of fractions onto MALDI plate targets • Flow rates: 1 nanoliter/second – 0.6 microliter/second • Dot sizes: 400–1500 micron at spraying distances of 500–2000 micron, respectively • Silicon- or Peek capillary outer diameters: 100–360 micron