Tissue engineering (TE) combines methods of cells, engineering and materials to improve or replace biological functions of native tissues or organs. Fabricating scaffolds is a vital process in TE for the mechanical support of the cells proliferation with desired functions and intricate structures. A pneumatic dispensing system of 3D printing is used to build soft scaffolds with controllable pore sizes in this research. An effective method is required to help users to systematically select proper parameters to print hydrogel strands with desired widths to fabricate scaffolds. In this research, printing parameters are classified first to build a simplified mathematical model to identify the significant parameters. A factorial experiment is then conducted to investigate effects of selected parameters and their interactions on the strand width. The solution is further verified using single variable experiments with the regression test. Based on the results, a parameters selection method is proposed and evaluated using two verification tests. A comparison test of the scaffolds fabrication is conducted to verify the analytic solution of the proposed theory. It is found that the nozzle sizes, dispensing pressure, and moving speed of a printer head all statistically affect strand widths. Among them, the nozzle size has the most significant influence on strand widths. Factors interactions are mainly embodied in between the nozzle size - moving speed and the nozzle size - dispensing pressure. In addition, a statistical significant linear relationship is found between the moving speed - strand width and the dispensing pressure - strand width. Furthermore, due to the high cost of bio-materials and the high pressure threat of air compressor in the dispensing system, a 3D bio-printing simulation system is developed to demonstrate the system configuration and operation procedures to help new users avoiding operation mistakes in the real world. A haptic-based 3D bio-printing simulation system with the haptic feedback is presented by means of the Phantom Omni haptic interface. The virtual environment is developed using the Worldviz software. The haptic force feedback is calculated based on the spring-damper model and the proxy method. This system is verified using questionnaire survey to provide a flexible, cost-effective, safe, and highly interactive learning environment. / February 2016

Laser surface modification of AZ31B Magnesium alloy changes surface composition and roughness to provide improved surface bio-wettability. Laser processing resulted in phase transformation and grain refinement due to rapid quenching effect. Furthermore, instantaneous heating and vaporization resulted in removal of material, leading the textured surface generation. A study was conducted on a continuum-wave diode-pumped ytterbium laser to create multiple tracks for determining the resulting bio-wettability. Five different laser input powers were processed on Mg alloy, and then examined by XRD, SEM, optical profilometer, and contact angle measurement. A finite element based heat transfer model was developed using COMSOL multi-physics package to predict the temperature evolution during laser processing. The thermal histories predicted by the model are used to evaluate the cooling rates and solidification rate and the associated changes in the microstructure. The surface energy of laser surface modification samples can be calculated by measuring the contact angle with 3 different standard liquid (D.I water, Formamide, and 1-Bromonaphthalen). The bio-wettability of the laser surface modification samples can be conducted by simulated body fluid contact angle measurement. The results of SEM, 3D morphology, XRD, and contact angle measurement show that the grain size and roughness play role for wetting behavior of laser processing Mg samples. Surface with low roughness and large grain size performs as hydrophilicity. On the contrast, surface with high roughness and small grain size performs as hydrophobicity.

Aortic stenosis is a serious cardiovascular disease that requires urgent attention and surgical intervention. If not treated, aortic stenosis can result in heart attack or cardiac arrest. Transcatheter Aortic Valve Replacement is a surgical technique that is used to treat aortic stenosis. Like all heart surgery, the procedure is difficult to perform and may lead to life-threatening complications. It is therefore important for a surgeon to be able to plan and rehearse the surgery before the operation to minimise risk to the patient. A detailed study was carried out to develop a 3D-printed, improved surgical tool for patient-specific planning and rehearsal of a Transcatheter Aortic Valve Replacement procedure. With this new tool, a cardiologist will be able better to understand a specific patient’s heart geometry and practice the procedure in advance. Computer tomography images were processed using image segmentation software to identify the anatomy of a specific patient’s heart and the surrounding blood vessels. Using materials design concepts, a polymer composite was developed that is able to mimic the mechanical properties of aortic tissue. State-of-art multi-material 3D printing technology was then used to produce a replica aorta with a geometry that matched that of the patient. An artificial aortic valve, identical to the type used in the Transcatheter Aortic valve replacement procedure, was then fitted to the replica aorta and was shown, using a standard test, to be a good fit with no obvious leaks. / Aortastenos är en hjärtsjukdom som får mycket uppmärksamhet och kräver kirurgi på grund av dess katastrofala komplikationer. Den allvarligaste komplikationen av aortastenos är hjärtinfarkt och resulterande hjärtstopp. Transcatheter Aortic Valve Replacement är en kardiovaskulär intervention som erbjuds för patienter med aortastenos. Denna typ av hjärtkirurgi är komplex och kan orsaka livshotande situationer för patienten om något går snett under operationen. Det är därför viktigt för kirurgen att kunna planera ingreppet innan han eller hon utför själva operationen för att minimera fara för patienten. Denna detaljerade studie ämnar utveckla och förbättra det kirurgiska verktyget för preoperativ planering av Transcatheter Aortic Valve Replacement genom 3D- tryckning. Forskningsarbetet kommer att ge kardiologer ett nytt sätt att förstå patientens hjärta i detalj och ett ökat förtroende för att träna på ingreppet på förhand. Datortomografibilder behandlades med hjälp av en bildsegmentationsprogramvara för att kunna skapa en anatomiskt korrekt kopia av patientens hjärta och tillhörande kärl. Genom att applicera material-vetenskapslära kan ett nytt kompositmaterial utvecklas med exakt samma mekaniska egenskaper som naturlig aortavävnad. Den mest moderna 3D-trycktekniken användes sedan för att producera en patientspecifik aorta. En artificiell aortaklaff placerades i den nyproducerade aortamodellen och tester visade en perfekt matchning utan läckage.

This thesis is concerned with acknowledging farm animals and their co-presence in the more-than-human space of the livestock farm, and with accounting for them responsibly in sustainability debates. The enrolment of farm animals as actors in political agendas for environmental sustainability, and farm animal welfare suggests that there are new ways of seeing and being with farm animals that permit their relational presence and recognise their subjectivity. Indeed geographers have in recent years acknowledged animals and their relations with humans, and they have begun to recognise the nature of animal subjectivies. However, within the fundamental rethinking of animals that has been provoked by these discussions, I suggest that farm animals have remained relatively invisible. Occupying ethically confusing terrain, farm animals have nonetheless been visible in a set of philosophical positions regarding their moral status, yet these debates present a rather confusing picture in which the farm animal as an individual is conspicuous by its absence. In seeking to redress the invisibility of farm animals within these debates, and recast them in relation to humans and the broader farm ecology, this thesis attempts to set out an epistemological and methodological framework through which farm animals might become visible as individual fleshy beings. Drawing on the concept of agricultural stewardship and new agendas in farm animal welfare science, it makes use of new methodological tools that have emerged in the social sciences to conduct a relational study of the livestock farm; a study in which farm animals themselves participate. It also considers how the divisions that have been constructed between humans, farm animals and the environment can be reconfigured as a more unified political science of the livestock farm.