Studies on Ejection of Cell Culture Medium by Electrohydrodynamic Method

Sample deposition based on micro-droplet ejection has broad application prospects in the field of biomedicine. Ejection of RPMI-1640 medium (without and with cells) is investigated experimentally using a home-build electrohydrodynamic (EHD) ejection system, consisting of a liquid supplier and a nozzle, a high voltage source, a droplet collector, and a high speed photography module. Electric voltage is applied between the nozzle and the droplet collector. The liquid surface is charged and the ejection takes place when electric force overcomes the surface tension. The ejection process is studied by using high speed photography and image processing. At low voltage, a uniform ejection state is established with ejection frequency typically less than 50Hertz. At sufficiently high voltage, another uniform ejection state is reached with ejection frequency as high as 1300Hz. Human peripheral blood mononuclear cells, after ejection, show survival rates higher than 79%, manifesting EHD ejection as a promising technique for cell printing