A-4 Echo Liquid Handler User ManualA.4 Fluid transferAfterthe fluid survey, the Echo software uses dynamic, real-timemeasurements to check the fluidlevel again and adjust the focus and poweras necessary to compensate for any changes immediately before dropletsare transferred from each well.A.4.1 Positioning the ADE elementsBefore a droplet can be ejected, the source plate gripper stage and theacoustic transducer stage are moved on their X- and Y-axes, so that thetransducer is centered directly below the source microplate well from whichfluid will be ejected. The appropriate destination microplate well ispositioned directly above the acoustic transducer and source microplatewell.The acoustic transducer assembly includes a fixed focal length lens. InFigure A.1 below, two adjacent wells with different fluid fill heights areshown. Before a droplet can be ejected, the acoustic transducer must bepositioned vertically on its Z-axis to correctly focus the acoustic energy nearthe fluid’s meniscus.Figure A.1 Fixed focal length dictates Z-axis adjustmentA.4.2 Creating the acoustic pulseThe acoustic pulse frequency, amplitude, and duration are calculateddepending on the fluid volume to be transferred, the composition of thefluid, individual acoustic transducer performance, and other factors.The Echo liquid handler builds up larger volume transfers by ejectingmultiple 2.5 nL droplets. The multi-droplet ejection from a single well willvary depending on the fluid composition and well fluid thickness (height).
