Katie Allison

Dept. Of Electrical Engineering & Computer Science



Katie Allison is going into her second year of Engineering Science at the University of Toronto. Over the course of the summer, Katie will be working in Professor Grau’s laboratory using a 3D printer and various testing equipment. Her work involves the modelling, fabrication, and testing of small-scale channels with hydrodynamic focusing.  By the end of the summer, Katie is hoping to have developed a novel hydrodynamically focused nozzle for printing large-area electronics like wearable electronics and displays. This will require her to design a focusing system optimized for reliability and miniaturization of the ink flow through iterative fabrication and testing. The goal of this project is to maintain small feature size and reliable results while allowing high speed additive printing with a low cost and easily fabricated nozzle. Doing so would make the printing of large-area electronics much faster and less expensive.


Development of a Hydrodynamically Focused Nozzle for Printing Electronics
Traditional microfabrication techniques for electronics create features with high resolution, but at relatively high cost and low throughput. Printing electronics using additive methods greatly lowers cost per unit area, and enables large area applications like displays to be quickly created on various substrates. Printed electronics manufacturing would benefit from a nozzle that is inexpensive and easily fabricated, yet able to print features tens of micrometers in width. The goal of this project was to design, fabricate, and test a microfluidic chip that would function as a hydrodynamically focused nozzle to print using a thin stream of ink with high resolution and reliability. It would use a sheath flow to compress either side of the ink flow such that the final stream is narrower than the internal nozzle diameter. This overcomes a major limitation of traditional nozzles where ink is forced directly out of the nozzle, which severely limits resolution and constrains ink parameters such as mass loading. This work aimed to create an easily reproducible nozzle by designing for the manufacturing limits of a 3D printer. A nozzle was designed in Solidworks, then prototyped using an Ultimaker 3 printer in CPE+ filament and iteratively optimized to suit the printer capabilities. Fluid flow and focusing effect were analyzed by observing pressure-driven flow through a partial nozzle bonded to glass, using dyed water to simulate the sheath fluid and ink. Early designs were able to successfully narrow a stream of water, which shows that the required focusing nozzle can be created. Future work will explore different fluids that can be used as functional inks. This will enable electronics to be printed using a focusing nozzle to yield high resolution conductive lines at low cost.