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PicoFill-Systems Outlicensing 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. 1 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. 2 Spraying of Arrays of Dots A. Piston pushes liquid through syringe while electric field is applied B. Slide is moved downward to lower the electric field: spraying stops 1–2 kV Spray of droplets MicroArray or slide C. Slide is moved upward and spraying resumes 1-2 kV 1-2 kV Spot Slide is moved downward and sideways: typical 200 – 1000 micron Second spot is sprayed onto slide 3 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 4