Steady cone-jet mode of electrospray for single-cell deposition

Abstract

We propose using the electrospray cone-jet mode operated near its minimum-flow-rate stability limit for single-cell deposition. Because the jet is much thinner than the cells themselves, individual cells can be clearly visualized or detected during deposition. At such low flow rates, individual cells can be placed at distinct, user-defined locations, even at relatively high cell concentrations. In this sense, our approach provides a spatial resolution at the scale of a single cell. We demonstrate the method's capabilities by depositing cells onto a millimeter-scale droplet of a standard cell-culture medium. Cell viability assays indicate that many cells maintain membrane integrity after exposure to the electrosprayed liquid, suggesting that most damage is reversible.

Figures (8)

• Figure 1: Sketch of the experimental setup to visualize the cone-jet mode of electrospray: syringe pump (A), feeding capillary (B), metallic plate (C), cubic chamber (D), DC high-voltage power supply (Bertan 205B-10R) (E), suction pump (F), high-speed camera (G), optical fiber (H), optical table (I), and (J) orientation system.
• Figure 2: Sketch of the experimental setup to visualize cell-by-cell deposition: droplet of cell culture medium (A), glass slide (B), stepper motor (C), cubic chamber (D), metallic plate (E), and (F) feeding capillary.
• Figure 3: Electrospray liquid cone. The labels indicate the time measured in milliseconds. The arrows point to the cells.
• Figure 4: Sequence of images of the cone tip showing the steady cone-jet mode re-stabilization after cell ejection.
• Figure 5: Normalized total grey intensity $I$ of the images acquired during the ejection of cells. $I=0$ corresponds to the mean grey intensity of all the images. The red circles indicate the instants at which the cells were ejected.