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Gastro-esophageal reflux disease (GORD) is common and a variety of surgical repair techniques have been shown to be effective. This thesis contains two randomised controlled trials and a combined data analysis of both studies to establish which techniques appear the most effective in controlling reflux. It also contains a pilot study to determine whether intraoperative manometry can predict which patients are likely to suffer from postoperative dysphagia. One hundred and three underwent partial fundoplication (Anterior or Posterior) and one hundred and twenty one patients underwent total/subtotal (Nissen or Lind) in the randomised controlled trials and 40 patients were recruited into the intraoperative manometry study. Patients were followed up for 12 months and their change in symptoms recorded. In the partial fundoplication trial, patients who underwent posterior fundoplication had better control of symptoms compared to those who underwent anterior fundoplication at the 12 month follow up point. There was no difference between the groups who underwent Nissen and Lind fundoplication. When the studies were collated, the laparoscopic total/subtotal fundoplication appears to be superior in the control of reflux when compared to the laparoscopic partial fundoplication. Intraoperative manometry may be advantageous as the study does suggest that this investigation may be useful in predicting post-operative dysphagia.

Lightweight, energy-absorbing structures are needed in many areas where the protection and threat mitigation of fragile personnel and objects are essential. Hence, the investigation of development and characterisation of energy-absorbing materials are crucial. The recent advances in the additive manufacturing (AM) have enhanced the development of such structures in many aspects with precisely designed configurations of the internal structures. Given the range of potential materials, many possible variations exist compared to the traditional polymer-based foams. The advantages of rapid prototyping, enabled through AM, allows a streamlined design process in obtaining a structure of mechanical behaviour suitable for intended applications. In this work, the development and fabrication of a flexible polymer-based lattice structure with core strut variations are demonstrated. A re-entrant honeycomb unit cell based lattice structure is chosen in a sandwich configuration with the implementation and modification of core struts for further investigation. The designed lattices are fabricated using stereolithography (SLA), a type of vat photopolymerisation, utilising the Formlabs Flexible 80A® resin. The core struts are modified in terms of shape, density and number of inclusions within the internal structure of the lattice. The mechanical characterisation of the samples under uniaxial compression is carried out at the strain rates of 0.005, 0.9 and 108 s-1 and the appropriate experimental apparatus and the diagnostics are developed and used for this purpose. The stress-strain responses reveal that the variations in the core struts affect the overall deformation behaviour of the structure, as well as the strain rate dependence of the relevant mechanical parameters. Anisotropic nature of the lattices are also investigated by uni-axial compression of the lattices positioned at 45◦ and 90◦ angles. The theoretically obtained parameters, from the formulations only dependent on the relative density, and the parameters calculated from the measured values are evaluated and compared, providing the insight that the the structural geometries influence the characteristic behaviour of the lattices over relative density or the material, highlighting the significance of the chosen structural design of the lattices. Finally, the discussion of the research findings in terms of the recommended applications of the each sample type, the functional flexibility and adaptability are presented.