Precision micro-fabrication by gelatin patterning with electrostatically-injected droplet (ELID) method

In this paper, a precise line of gelatin was fabricated utilizing electrostaticallyinjected droplet (ELID) method. The goal of this study is to fabricate 3D structures of cells utilizing the ELID method. It is preferable to perform laboratory experiments with 3D structures of cells in tissue engineering and artificial organ. Inkjet technology was applied to fabricate 3D structures of cells. However, commercial inkjet technology was not enough to pattern liquid with biomaterials precisely because the viscosity of the liquid was high. Small droplets were ejected from a tip of a tube that was filled with liquid when the strong electrostatic field was applied to the water pin electrode. This phenomenon was named as Electrostatically- Injected Droplet (ELID) method. The ELID method had two good merits. Those were high resolution to print and ability to eject highly viscous liquid. These two merits were suitable to fabricate precise 3D structures of cells. It was demonstrated that living cells were not killed when the cells were ejected with the ELID method in spite of high voltage application. Current did not flow inside the cells but around the cells because the resistance value of the cell wall was a little higher than that of the liquid. It was required to pattern scaffolds between cells precisely to fabricate 3D structures of cells because the own weight of cells were above the bonding force between cells. Gelatin and collagen were typical examples of the scaffolds. The purpose of this paper was to pattern precise line of gelatin utilizing the ELID method. The experimental set-up consisted of the water pin electrode that was filled with the liquid with gelatin and a sheet of paper that was set on a plate electrode. Voltage was applied between these electrodes by a high voltage amplifier and a function generator. Gelatin was patterned when the plate electrode was moved in x and y directions with two linear stages. The viscosity of the liquid with gelatin was low when the temperature of the liquid was high. When the temperature was over 40 degrees Celsius, cells were killed by heat. In consideration of these two matters, the experimental set-up was set in the condition that the temperature was 38 degrees Celsius. The fundamental characteristics to pattern liquid with gelatin utilizing the ELID method were investigated. The precise line of gelatin was patterned with this experimental set-up. The width of the line was about 6 micron meters. It was fine enough to be used as scaffolds because the diameter of cells was about several 10 micron meters.