Three-dimensional (3D) printing has a high potential in various biomedical applications. We hypothesise that 3D printing could be a viable option to construct bioimpedance spectroscopic (BIS) sensors suitable for electrochemical characterization of oral mucosal tissues. Previous BIS studies have been relied on hand-made probes possessing significant limitations related to single patient disposable use, great inter-probe differences and weak reproducibility of measurement. There is also uncertainty related to effect of varying loading pressure between the probe and biological tissue. Here, we introduced three different sized rectangular shaped 3D printed probes and test those using four-terminal measurement principle on various porcine oral tissue samples. We found that constructing fully 3D printed probe is a challenging task and prone to issues relating to short circuiting or electrochemical corrosion. However, our final protype version constructed with silver-coated copper electrodes showed favourable characteristics in BIS experiments. All three different sized probes were able to differentiate between different tissue types with excellent reproducibility. The effect of loading pressure was found to be almost negligible when using small and medium sized probes. However, further studies are needed to measure tissues with uneven surfaces, such as palatinum, and to avoid manual or electrochemical surface finishing steps.
This study is an interesting industrial case study for the application of a validated flashing and hydraulic shock modelling approach to the safety and design of a reactor blow line. The maximum flow rate is important for sizing of downstream components. The high pressure of the blow and flashing of the liquid can result in significant forces on pipe bends and other geometrical features. Analysis and prediction of such forces are of importance for the structural design and anchoring of the piping. Another concern for a liquid blow under high pressure is the potential for condensation-induced hydraulic shock. The collapse of the flashed vapor to the liquid phase creating shock waves of large amplitudes is a serious safety concern.
The CFD model used the homogeneous mixture model with a flashing model for phase change of the fluid. The properties of the fluid were defined by a custom function which interpolated between tabulated values of the thermodynamic and transport properties. The CFD simulations confirmed the risk of condensation hydraulic shock when the blow down is initiated with empty pipes and also demonstrated that a hydraulic shock could be prevented with liquid-filled condition. The pipework geometry was also optimized to reduce the forces acting at the junctions. The vapour quality at the outlet as a result of flashing was estimated which is necessary for the design of downstream systems.
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