Development of a direct three-dimensional biomicrofabrication concept based on electrospraying a custom made siloxane sol

Abstract

We demonstrate here the discovery of a unique and direct three-dimensional biomicrofabrication concept possessing the ability to revolutionize the jet-based fabrication arena. Previous work carried out on similar jet-based approaches have been successful in fabricating only vertical wallpillar-structures by the controlled deposition of stacked droplets. However, these advanced jet-techniques have not been able to directly fabricate self-supporting archeslinks (without molds or reaction methods) between adjacent structures (walls or pillars). Our work reported here gives birth to a unique type of jet determined by high intensity electric fields, which is derived from a specially formulated siloxane sol. The sol studied here has been chosen for its attractive properties (such as an excellent cross-linking nature as well as the ability to polymerize via polycondensation on deposition to its biocompatability), which promotes direct forming of biostructures with nanometer (<50 nm) sized droplets in three dimensions. We foresee that this direct three-dimensional biomicrofabrication jet technique coupled with a variety of formulated sols having focused and enhanced functionality will be explored throughout the physical and life sciences.

Figure 1

A schematic representation of the three ground electrode geometries investigated during jetting in the stable cone-jet mode, namely, (a) the ring-shaped ground electrode which forms a cone-shaped spray diverging droplets with finer droplets based on the extremities of the spray which recirculate, (b) a plate-shaped electrode which has a similar effect much like that of the ring but does not have droplet recirculation, and (c) a point-shaped electrode which converges the spray to the head of the point assisting in the deposition of a large majority of droplet residues with precision.

Figure 2

Characteristic transmission electron micrographs of (a) micrometer and (b) nanometer sized droplet residues for an applied voltage to flow rate of ∼10∕11 kV and ∼10⁻⁹ m³ s⁻¹ for a ground electrode distance of ∼15 mm from the exit of the needle, respectively.

Figure 3

Characteristic scanning electron micrographs of the fabricated structures for a ring electrode geometry, with (a) showing the area which has been fabricated with the region centrally placed below the ring having several assembled but randomly located structures and (b) elucidating a high magnification of the surface topography of the surroundings having a formation much like a coral reef. These structures were very similar when compared with those formed for a plate type electrode configuration.

Figure 4

(a) Schematic representation of the fabrication path followed by the needle and ground electrode in turn for microfabricating the three-dimensional architecture seen in (b).

Figure 5

Representative scanning electron micrographs showing (a) the finally fabricated structure following the stages depicted in Fig. 4 and (b) the fine features fabricated by means of this processing technique. This micrograph (5b) depicts in high magnification the top most structure. The micrographs also elucidate the mixed surface texture, which is currently under investigation.

Figure 6

Typical optical micrograph depicting the positively proliferating smooth muscle cells after seeding for 48 h on the microslide which was exposed to the spray of sol for ∼1000 s.

Figure 7

A schematic representation of the authors intended microfabrication device which will be explored for the fabrication of controlled three-dimensional structures by electric field directed assembly for the creation of complex structures in the micrometer range.