3D printed conducting polymer microstructures as an ultra-low velocity flow sensor

Abstract

To develop devices for improving the quality of life such as handheld electronics, artificial muscles, lab-on-chip devices, etc., the quest for future smart materials has led to increasing interest in Conducting Polymers (CPs). Recent technological advancements have already exploited the many advantages of CPs, but to further their usability, we require a reliable and robust means of fabricating CPs at micrometric scales. This research work focusses on demonstrating these fabricated CP micro-structures’ applicability in biomedical applications and, more specifically, as a means of sensing and measuring air flow levels observed during neonatal resuscitation. In this thesis, I present a reliable means of fabricating three-dimensional CP microstructures, in particular focusing on fabricating hair-like microstructures from Poly(3,4-ethylenedioxythiophene) Poly(styrene sulfonate), referred to as PEDOT:PSS. A 3D printer was developed with capabilities of producing microscopic patterns and structures using miniaturized pipettes for dispensing the CP material. A Graphical user interface was also developed to allow human interface with the microstructure printer. A novel flow sensor prototype was developed using PEDOT:PSS micro-hairs, where these micro-hairs act as microscopic switches which open and close in response to air flow. By using an array of micro-hairs that respond to specific flow velocities, a discrete digital output flow sensor was demonstrated. A means of improving the sensitivity of the flow sensor to lower flow velocities was also demonstrated by printing the micro-hairs within a narrow convergent-divergent flow channel. To improve the understanding of the flow sensor’s response to air flow by simulating the Fluid-structure interactions (FSI), a robust mathematical model was developed. Based on Lattice Boltzmann equations for simulating the fluid flow in a 3D domain and beam theory for simulating large deflections, the model was exclusively coded in MATLAB. Using dimensional transformations to minimize the computational costs, a mixed 2D and 3D simulation for the developed FSI model is presented. Using the FSI model, a final sensor prototype was developed specifically to be compatible with the target neonatal resuscitator device. Apart from being capable of measuring the ultra-low velocity flows experienced during neo-natal resuscitation to meet the demands of the target application, this prototype sensor was designed to be portable with the capability of reading out flow levels directly integrated with the sensor. Furthermore, the portable sensor was also developed with a disposable architecture to improve medical compatibility. By successfully demonstrating the capabilities of fabricating CPs in micrometric scales and using these microstructures as a suitable means of sensing air flow through the development of an ultra-low velocity flow sensor, the suitability of using CP microstructures in real world applications has been demonstrated.