Product miniaturization has created a need for novel manufacturing methods capable of producing complex geometries with resolutions in the nano- and micro- scales. Ideally these new micro- and nano- manufacturing techniques should have high throughput and multi-material capabilities.
Fig. 1 - Current micro- and nano-manufacturing technology landscape. Technologies with single-micron and sub-micron resolutions capable of producing complex shapes are not currently available.
Near Field Electrospinning (NFES) is an additive manufacturing process that can achieve micron and submicron resolutions. This process uses electrohydrodynamic phenomena to create continuous micro and nano fibers (diameters have been reported as low as single digit nanometers and up to several microns). The fibers can be deposited in a moving collector to generate 2D and 3D structures. NFES has been shown to be compatible with hundreds of polymers. It can also print some metals, ceramics, carbon fiber, and carbon-nanotubes with additional post processing.
NFES has to overcome challenges in control, throughput, and repeatability to become a viable manufacturing technique. An additional challenge is that the science behind NFES is not fully understood. We have developed a NFES setup that will allow for testing of new techniques for improving the process and for studying the physical phenomena involved. Currently, we are studying the feasibility of electric field modifications to control the fiber deposition process. The electric field modification is achieved by using auxiliary electrodes and modifying the geometries of the electrodes required for NFES. This should allow for tighter resolutions and increased repeatability. A multiphysics model is being developed to aid in the design of the setup. The model will be extended to solve backward control problem, i.e. predict the required parameters for obtaining a desired geometry. The development of the model will help improve the scientific understanding of NFES.
Fig. 2 - NFES experimental setup
Fig. 3 - Experimental results show that incorporation of an auxiliary electrode can improve repeatability in fiber deposition.
Fig. 4 - Conceptual electrode ring designs for fiber control. The control is based on electrode piezo-actuation (left) and electrode potential variation through time (right).
Fig. 5 - Electric field modelling for different NFES geometries. Electric potential contours, electric field, and electric field streamlines for needle-plate (top) and needle-needle (bottom) geometries with no electrode ring.
National Science Foundation (CMMI – 1404489)