S. N. Jayasinghe

Electrohydrodynamic jetting of mouse neuronal cells

CAD (Cath.a-differentiated) cells, a mouse neuronal cell line, were subjected to electrohydrodynamic jetting at a field strength of 0.47-0.67 kV/mm, corresponding to an applied voltage of 7-10 kV. After jetting, the cells appeared normal and continued to divide at rates similar to those shown by control samples. Jetted cells, when placed in serum-free medium, underwent differentiation that was sustained for at least 1 month. Some of the droplets produced by jetting contained only a few cells. These results indicate that the process of jetting does not significantly perturb neuronal cells and that this novel approach might in the future be a useful way to deposit small numbers of living nerve cells on to surfaces.

Controlled deposition of nanoparticle clusters by electrohydrodynamic atomization

A suspension containing 20?nm silica particles in ethylene glycol was subjected to electrohydrodynamic atomization (EHDA) in the stable cone-jet mode using a ring-shaped ground electrode. The droplets produced were sized by laser diffraction and were in the range 0.5?20??m. Immediately after deposition, droplet relics were analysed by optical microscopy and were found to be in the size range 1?80??m. Subsequently, using a pointed rod-electrode (rather than a ring), and by increasing the intensity of the electric field and by reducing the flow rate of suspension subjected to EHDA, relics of in size were deposited using a patterning device. In both of the above instances, the relics contained two distinct zones, an outer ring of ethylene glycol and a much smaller dense inner region of silica nanoparticles. These results show that, by using EHDA, a novel controlled deposition method of nanosuspensions has been developed.

Instrument for electrohydrodynamic print-patterning three-dimensional complex structures

A print-patterning instrument coupling electrohydrodynamics and servo and stepper motor motion has been developed. It has been used to pattern and form a 10mm×30mm rectangular walled container from zirconia. The incorporation of electrohydrodynamics allows the generation of finer droplets, compared with ink-jet technology, from a concentrated two-phase medium. The precision servo/stepper system consists of a three-axis motion planner, which is computer controlled and allows three cradles to be in motion according to a predetermined sequence created on any computer aided design package. The problems encountered in forming three-dimensional (3D) structures using this method are explained and possible solutions incorporating future work are discussed. This instrument has the potential of being developed into a powerful device for 3D solid freeform fabrication of structural, functional, and biological structures.

Electric-field driven jetting from dielectric liquids

Three dielectric (electrical conductivity ∼10−13Sm−1) Newtonian liquids with viscosity in the range 1–100 mPa s were passed through a needle at a controlled flow rate under the influence of an electric field. At an electric field strength of 1.5kV∕mm, the liquid exiting the needle instantaneously transformed from dripping droplets to an elliptically pendent droplet from the apex of which a fine jet evolved. Thus, a jet can be obtained on demand, and in this letter we define this phenomenon and explain a basis for it.

Preparation of collagen films by electrostatic atomization

The processing of collagen and chitosan, which exhibit tremendous potential as bioactive materials, has generated a great deal of interest in the last few years (e.g., [1, 2]). In particular, the preparation of collagen [3] and collagen-chitosan films [4] and investigation of their electrical properties has been explored. In a recent letter we were able to produce chitosan films by electrostatic atomization [5] and in this communication we show that ∼30 μm collagen films can also be prepared using the same technique. 35 wt% of water soluble collagen (Type Semed F, supplied by Kensey Nash Corporation, Exton, USA) was dissolved in single distilled water by mixing for 48 h in a beaker using a magnetic stirrer. The density (density bottle method), viscosity (calibrated reverse flow U-tube), surface tension (calibrated Du Novy balance), dc conductivity and relative permittivity (using calibrated cells) of the collagen solution was measured as described previously [6] after calibrating each with single distilled water. Electrostatic atomization was carried out using the set-up shown in Fig. 1 where the stainless steel needle has an inner diameter of 200 μm. The ring-shaped ground electrode is held 8 mm below the exit of the needle. Freshly prepared collagen solution was syringed to the needle at 3 × 10−9 m3 s−1 with the applied voltage set at 8 kV. Under these conditions, with the ammeter in Fig. 1 reading 57 nA, stable cone-jet mode electrostatic atomization was achieved (Fig. 2).