3D Jet Writing - Controlled Deposition of Multicomponent Electrospun Fibers in Three Dimensional Space.

Abstract

Electrospinning is a fiber fabrication technique which has potential use in applications ranging from filters and sensors to regenerative medicine. Generation of multi-component fibers and particles is possible through the use of a technique called electrohydrodynamic co-jetting. Despite the many applications, the process suffers from two main limiting factors. First, the reliance on a bicompartmental fluid interface inherently limits the scalability of the system. Secondly, the random fiber placement resulting from a process instability leads to limited pore sizes and uncontrollable 3D architectures. Herein, both of these factors are addressed independently. Scalability was addressed by creating a device which creates an extended fluid interface composed of two polymer solutions. This method was shown to produce bicompartmental fibers and particles at throughputs in excess of 30 times greater than traditional methods while retaining consistent fiber size distributions. Next, a method of completely eliminating the whipping instabilities associated with the electrospinning process, called 3D jet writing, was shown to be capable of perfectly stacking of fibers on top of one another. This process utilizes radially directed electric fields to dampen the formation of whipping instabilities, and a moving collection electrode to produce 3D fiber geometries. Deposition of fiber lines within approximately 15 µm is achieved using this system, making direct writing of fiber stacks within 0.3° of perfectly parallel, and 1.1° of perpendicular, and fabrication of three-dimensional scaffolds with regular tessellated prismatic pore architectures possible with this technique. The precision afforded by this technique was used to create 3D high-density stem cell culture environments which contain up to 1.4 million cells/mm3 polymer material, with 96% of the scaffold volume consisting of open area for 3D cell growth. These scaffolds allow for 3D cell culture to be tessellated across large areas, addressing common limitations associated with other 3D culture techniques. When differentiated osteogenically, stem cell microtissues can promote healing of calvarial defects in mice, producing on average over three times the new bone volume compared to the control groups. Similar tessellated differentiated stem cell microtissues were also able to simulate a diseased tissue by promoting metastasis in anomalous anatomic sites in 5/5 cases.