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Title: A prototype for 3D electrohydrodynamic printing
Author: Hashimdeen, S. H.
ISNI:       0000 0004 7659 3519
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2016
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Electrohydrodynamic direct writing is a flexible cost effective alternative technique that is capable of producing a very fine jet of liquid in the presence of an external electric field. This jet can then be used to pattern surfaces in an ordered and controlled fashion and offers a robust route to low cost large area micro and nano-manufacturing. Unlike other types of direct writing techniques, the liquid in electrohydrodynamic printing is subjected to both pushing and pulling forces. The pushing force is brought about by the constant flow rate that is maintained via high precision mechanical pumps while a pulling force is applied through a potential difference that is applied between the nozzle and the ground electrode and as a result a fine jet can be generated to pattern surfaces. The impracticality of use and the cost of building micrometre and sub-micrometre sized nozzles to print narrow line widths warrant an investigation into alternative means of dispensing printing inks using nozzles that are cheap to produce, easy to handle and consistent in delivery. The enormous capillary pressures that would have to be overcome in order to print highly viscous materials with micrometre and sub-micrometre sized nozzles may also limit the types of feed that could be used in printing narrow line widths. Thus, the initial work described is focused on improving print head design in an attempt to electrohydrodynamic print pattern narrow line widths using silk fibroin. This is followed by work where we attempt to design and construct of a new electrohydrodynamic printing machine with the sole purpose of expediting research in electrohydrodynamic printing in a flexible, feasible and user friendly manner. To achieve this, replicating rapid prototype technology is merged with conventional electrohydrodynamic printing phenomena to produce a EHD printing machine capable of print depositing narrow line widths. In order to validate the device the work also describes an attempt to print a fully formed human ear out of polycaprolactone. Finally, we investigate an approach to the electohydrodynamic printing of nasal septal scaffolds using the microfabrication system that was developed and optimized in our laboratory. In these initial stages we were successful in showing the degree of control and flexibility we possess when manufacturing constructs out of a biodegradable polymer ( polycaprolactone) from the micro to macro scale through manipulation of just one process parameter (concentration). This work also features characterization of scaffold mechanical properties using a recently invented Atomic force microscopy technique called PeakForce QNM (Quantitative Nanomechanical Property Mapping).
Supervisor: Edirisinghe, Mohan Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available