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Purpose. This study aims to investigate the effect of the material thickness and build orientation on the mass transfer of low molecular weight substances through polyamide 12 (PA12) structures produced by laser sintering (LS). Design/methodology/approach. Disc-shaped PA12 sheets having a nominal thickness ranging from 700 to 2,000 µm were built in horizontal, vertical and diagonal orientations and their permeation properties to oxygen and water vapor were measured. The structural properties of the sheets were examined by X-ray micro-computed tomography, differential scanning calorimetry and polarized light microscopy. Findings. All the LS sheets that were investigated had water vapor and oxygen permeation coefficients that are in the range of those of PA12 produced by traditional manufacturing technologies. Despite significant differences in the porosity characteristics, the permeation properties of sheets built in different orientations were similar. The pores seem to have no measurable effect on the mass transfer rates in the sheets, and the transport processes seem to predominantly follow the rules of a regular solution-diffusion mechanism. The results showed a non-significant trend toward thickness-dependent permeation coefficients, which agrees with the observed differences in the crystal structures of the sheets. Practical implications. The results are an important basis for the qualification of LS technology for direct manufacturing in applications requiring special barrier performance. Originality/value. This study provides new information on mechanisms of mass transport through LS PA12 and the effect of the material thickness and build orientation. Furthermore, the results enhance understanding of the structural properties of thin polymeric sheets produced by LS.

Background: Patients' access to their computerised medical records (CMRs) is a legal right in many countries. However, little is reported about the benefit-risk associated with patients' online access to their CMRs. Objective: To conduct a consensus exercise to assess the impact of patients' online access to their CMRs on the quality of care as defined in six domains by the Institute of Medicine (IoM), now the National Academy of Medicine (NAM). Method: A five-round Delphi study was conducted. Round One explored experts' (n = 37) viewpoints on providing patients with access to their CMRs. Round Two rated the appropriateness of statements arising from Round One (n = 16). The third round was an online panel discussion of findings (n = 13) with the members of both the International Medical Informatics Association and the European Federation of Medical Informatics Primary Health Care Informatics Working Groups. Two additional rounds, a survey of the revised consensus statements and an online workshop, were carried out to further refine consensus statements. Results: Thirty-seven responses from Round One were used as a basis to initially develop 15 statements which were categorised using IoM's domains of care quality. The experts agreed that providing patients online access to their CMRs for bookings, results, and prescriptions increased efficiency and improved the quality of medical records. Experts also anticipated that patients would proactively use their online access to share data with different health care providers, including emergencies. However, experts differed on whether access to limited or summary data was more useful to patients than accessing their complete records. They thought online access would change recording practice, but they were unclear about the benefit-risk of high and onerous levels of security. The 5-round process, finally, produced 16 consensus statements. Conclusion: Patients' online access to their CMRs should be part of all CMR systems. It improves the process of health care, but further evidence is required about outcomes. Online access improves efficiency of bookings and other services. However, there is scope to improve many of the processes of care it purports to support, particularly the provision of a more effective interface and the protection of the vulnerable.