Technologies That Enable Accurate and Precise Nano- to Milliliter-Scale Liquid Dispensing of Aqueous Reagents Using Acoustic Droplet Ejection

Abstract

Acoustic liquid handling uses high-frequency acoustic signals that are focused on the surface of a fluid to eject droplets with high accuracy and precision for various life science applications. Here we present a multiwell source plate, the Echo Qualified Reservoir (ER), which can acoustically transfer over 2.5 mL of fluid per well in 25-nL increments using an Echo 525 liquid handler. We demonstrate two Labcyte technologies-Dynamic Fluid Analysis (DFA) methods and a high-voltage (HV) grid-that are required to maintain accurate and precise fluid transfers from the ER at this volume scale. DFA methods were employed to dynamically assess the energy requirements of the fluid and adjust the acoustic ejection parameters to maintain a constant velocity droplet. Furthermore, we demonstrate that the HV grid enhances droplet velocity and coalescence at the destination plate. These technologies enabled 5-µL per destination well transfers to a 384-well plate, with accuracy and precision values better than 4%. Last, we used the ER and Echo 525 liquid handler to perform a quantitative polymerase chain reaction (qPCR) assay to demonstrate an application that benefits from the flexibility and larger volume capabilities of the ER.

Determination of equilibrium dissociation constants for recombinant antibodies by high-throughput affinity electrophoresis

“…A recent study has shown that41 stochastic instabilities in the droplet trajectory can occur, possibly due to variable ADE energy requirements at the surface of the source liquid surface. And minimizing the distance between the source and destination reduces the CV in droplet placement due to the reduced time during which the error in trajectory can propagate, thus improving the precision of the droplet placement.…”

“…Focused high-frequency sound waves create a controlled pressure wave front that can be further excited near the fluid surface to generate and eject small droplets. Due to advances in computational speed and signal processing algorithms, ADE precisely controls droplet generation to yield predefined volumes and ejection speeds4041. We then characterized and applied the automated system to report K D for a six-member library of recombinant antibodies against eGFP.…”

Moving Liquids with Sound: The Physics of Acoustic Droplet Ejection for Robust Laboratory Automation in Life Sciences

“…The source plates used to transfer from were 384-well polypropylene microtiter plates. A variety of different well fluid volumes were used in the source plates (20,30,40, and 50 µL). For each source well volume studied, 20-drop transfers from 384 separate wells filled to that volume were measured, in order to obtain meaningful statistics.…”

“…27,28 The extension of the DFA methods to larger droplet size (25 nL) is described in another article in this journal, further confirming the value of DFA to bring robust liquid-transfer performance to ADE applications. 20 …”

Why a Special Issue on Acoustic Liquid Handling?

“…20 No longer is ADE restricted to a limited range of fluids (nor does it require liquid-by-liquid individual calibrations). The development of dynamic fluid analysis, as outlined by Sackmann et al, 21 generates automatic monitoring and calibrations of the system on a well-by-well basis in milliseconds. Buffers, solvents, 50% glycerol, or detergent-based solutions are automatically transferred with the same high precision as was developed for DMSO.…”