Abstract
Electrochemical sensors are devices used to measure chemical substances based on their electrochemical properties, primarily through reactions that produce or consume electrons. These sensors have found extensive applications in fields such as environmental monitoring, medical diagnostics, food safety, and industrial process control. Their appeal lies in their sensitivity, selectivity, and fast response times. In recent years, 3D printing, a type of additive manufacturing, has emerged as a promising technique for fabricating electrochemical sensors. The layer-by-layer construction allows for the creation of complex and customisable designs using a variety of conductive materials. One of the primary advantages of 3D printing is its ability to produce intricate sensor geometries that are difficult or impossible to achieve with traditional methods. Additionally, 3D printing reduces production costs by using fewer materials and fewer steps, making it particularly appealing for large-scale production or rapid prototyping. Since most 3D-printed filament materials have limited conductivity, various post-printing treatment strategies have been used to enhance the conductivity of 3D-printed electrodes. However, there is a notable lack of strategies both during and before the printing process to optimize these electrodes for immediate use.The focus of the papers in this thesis was related to producing ready-to-use electrochemical sensors using 3D printing. Papers 1 and 2 looked at utilising printing parameters to improve the sensitivity and kinetics of carbon black/polylactic acid (CB/PLA) sensors. In Paper 1, Electrodes printed at a speed of 60 mm/s exhibited the highest current and the most efficient electron transfer kinetics. In contrast, those printed at both higher and lower speeds showed increased resistance. Paper 2showed how different parameters, such as speed, nozzle and bed temperature, printer quality and nozzle size can influence sensor quality. We observed that extruder temperatures of 230°C and 240°C enhanced the electrochemical activity of CB/PLA electrodes, primarily due to increased surface roughness and a reduction in voids between print layers. Factors such as nozzle diameter, heated bed temperature and3type of 3D printers had no significant effect on the electrochemical performance of the electrodes. However, high-end printers reduced the batch-to-batch variability. Paper3 explored the pre-printing modification of commercial carbon thermoplastic filaments via saponification to selectively remove PLA. Our results showed that this treatment significantly improved the electrochemical performance of multiwalled carbon nanotube (MWCNT)/PLA and CB/PLA electrodes, with enhanced current responses and faster electron transfer kinetics for varying redox probes compared to electrodes made with native filaments. Paper 4 assessed the impact of reduced material infill on the performance of CB/PLA electrodes. We demonstrated that CB/PLA electrodes with30% infill performed comparably to those with 100% infill in terms of anodic current and electron transfer kinetics for redox probes. This reduction in material usage, which cuts CB/PLA consumption by 44%, presents a more sustainable approach to 3Dprinting electrochemical sensors. Lastly, Paper 5 investigated the influence of electrode architecture design on the electrochemical activity of mixed carbon/PLA materials without custom filament production. Electrodes with graphene as the outer structure and a lower-conductivity material as the inner component demonstrated the highest current and most efficient electron transfer kinetics for various inner and outer sphere redox probes. Conversely, electrodes with reduced internal path rotation exhibited higher resistance for the same probes.
In conclusion, this body of work demonstrates the potential of 3D printing technology in the fabrication of electrochemical sensors, with a focus on optimizing key parameters for enhanced sensor performance. The findings reveal that both the printing parameters and material modifications significantly impact the sensitivity and electron transfer kinetics of carbon-based electrodes. By fine-tuning factors such as printing speed, extruder temperature, and material infill, this research highlights the ability to produce efficient, high-performing sensors while reducing material consumption. Additionally, pre-printing treatments and creative electrode architecture designs were shown to further enhance electrochemical activity, offering a promising avenue for improving sensor functionality. Collectively, these outcomes suggest that3D printing can serve as a versatile and sustainable approach for the large-scale production of ready-to-use electrochemical sensors.
| Date of Award | Oct 2024 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Bhavik Patel (Supervisor) & Mark Yeoman (Supervisor) |