Medical device usability directly impacts the practitioner's ability to perform their diagnostic task in an effective, efficient, and safe manner. A device with poor usability may frustrate the practitioner, increasing the worker's stress level in a high-stress work environment. In addition, a device with poor usability may facilitate operator error, increasing the patient's risk of injury. Designers of healthcare systems and devices face a unique conundrum that has been documented in the literature (Martin, Murphy, Crowe, & Norris, 2006; Martin, Norris, Murphy, & Crowe, 2007; Ward & Clarkson, 2007). Standards require the use of user research techniques, yet patient privacy standards prevent designers from observing users in context. The inability to observe users in their work environment impedes understanding the context-of-use. Since understanding context-of-use is required to ensure usability, further exploration into alternative methods for requirements gathering is needed. This study explored the storytelling as an elicitation method for medical device requirements by comparing the information elicited from nurses during requirements gathering for an infusion pump by two methods: focus groups followed by interviews (Group #1) and focus groups followed by storytelling sessions (Group #2). Results suggest further exploration of storytelling is warranted as Group #2 contributed similar quantity and breadth of information in significantly less time. Results also indicate potential support for the efficacy of storytelling within the healthcare domain as Group #2 participants contributed more distinct context-of-use information with an emphasis on the social context. Contributions of this study include a plan for mixed-method data analysis, a protocol for conducting a storytelling session, and a framework for defining requirements within the healthcare domain. / Master of Science

Yes / We report the first application of a microfluidic device to observe chemotactic migration in multicellular spheroids. A microfluidic device was designed comprising a central microchamber and two lateral channels through which reagents can be introduced. Multicellular spheroids were embedded in collagen and introduced to the microchamber. A gradient of fetal bovine serum (FBS) was established across the central chamber by addition of growth media containing serum into one of the lateral channels. We observe that spheroids of oral squamous carcinoma cells OSC–19 invade collectively in the direction of the gradient of FBS. This invasion is more directional and aggressive than that observed for individual cells in the same experimental setup. In contrast to spheroids of OSC–19, U87-MG multicellular spheroids migrate as individual cells. A study of the exposure of spheroids to the chemoattractant shows that the rate of diffusion into the spheroid is slow and thus, the chemoattractant wave engulfs the spheroid before diffusing through it. / This work has been supported by National Research Program of Spain (DPI2011-28262-c04-01) and by the project "MICROANGIOTHECAN" (CIBERBBN, IMIBIC and SEOM). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Implantable medical devices face numerous complications when interfacing with soft tissue, and are plagued by negative responses from host tissue. One such class devices are percutaneous osseointegrated prosthetics (POP). POP consist of a bone anchored titanium post that extrudes through the skin and attaches to an external prosthetic. Compared to the traditional socket interface, POPs offer better stability, limb functionality, and osseoperception for both upper and lower prosthetic limbs. Although the POP surgery technique is well established, the main disadvantage to this technology remains the titanium (Ti) - skin interface. Some of the complications that can arise include epithelial downgrowth, mechanical tearing, and infection. Various types of coatings, surface structure, and antibiotic release technologies have been used to coat Ti in an effort to mitigate POP's associated obstacles, but these methods have failed to translate into published clinical studies and mainstream medical use. One potential solution may be to mimic an interface already found in the human body, the fingernail-skin interface, which is infection-free and mechanically stable. The same keratins that make up the cortex of human hair fibers are found in the fingernail. These cortical human hair keratins can be extracted and purified, and fingernail-specific dimeric complexes coated onto Ti surfaces using silane coupling chemistry. Keratin has been used in other studies for its cell adhesion and differentiation properties, and it has been suggested that the Leu-Asp-Val (LDV) amino acid motif is the primary site responsible for cellular attachment. In the present work, keratins extracted from human hair fibers and recombinant keratin nanomaterials (KN) were used to create biomimetic coatings on silanized Ti surfaces. These coatings were characterized and investigated for surface topography, elemental composition, cell adhesion motifs, and cell adhesion. Both keratin substrates showed the ability to create uniform coatings that retain a protein conformation that exhibits cell adhesion motifs. The coatings exhibit the ability to support cell adhesion of both epithelial and connective tissue cells. Application of fluid shear stress was used to test the mechanical adhesion strength of cells on keratin coatings. The structure, biochemical stability and sustained cellular adhesion of these coatings support keratin's capacity to provide a stable interface between POPs and skin. Side-by-side studies of extracted and recombinant keratins reveals that the recombinant form of these materials may provide distinct advantages for their use in POP devices. Overall, this study confirmed that a uniform, silane-coupled keratin coating was feasible. We demonstrated the substrates contain a biological function in terms of cellular adhesion and phenotypic changes in skin-relevant cells. These results support the biomimetic function of keratin on silanized Ti, which may provide a suitable coating to translate percutaneous medical device coating applications toward clinical use. / Ph. D. / Implantable medical devices face numerous complications when interfacing with soft tissue, and are plagued by negative responses from host tissue. One such class devices is percutaneous osseointegrated prosthetics (POP). POP consist of a bone anchored titanium post that extrudes through the skin and attaches to an external prosthetic. Compared to the traditional socket interface, POPs offer better stability, limb functionality, and osseoperception for both upper and lower prosthetic limbs. Although the POP surgery technique is well established, the main disadvantage to this technology remains the titanium (Ti) - skin interface. Some of the complications that can arise include epithelial downgrowth, mechanical tearing, and infection. Various types of coatings, surface structure, and antibiotic release technologies have been used to coat Ti in an effort to mitigate POP’s associated obstacles, but these methods have failed to translate into published clinical studies and mainstream medical use. One potential solution may be to mimic an interface already found in the human body, the fingernail-skin interface, which is infection-free and mechanically stable. The same keratins that make up the cortex of human hair fibers are found in the fingernail. These cortical human hair keratins can be extracted and purified, and fingernail-specific dimeric complexes coated onto Ti surfaces using silane coupling chemistry. Keratin has been used in other studies for its cell adhesion and differentiation properties, and it has been suggested that the Leu-Asp-Val (LDV) amino acid motif is the primary site responsible for cellular attachment. In the present work, keratins extracted from human hair fibers and recombinant keratin nanomaterials (KN) were used to create biomimetic coatings on silanized Ti surfaces. These coatings were characterized and investigated for surface topography, elemental composition, cell adhesion motifs, and cell adhesion. Both keratin substrates showed the ability to create uniform coatings that retain a protein conformation that exhibits cell adhesion motifs. The coatings exhibit the ability to support cell adhesion of both epithelial and connective tissue cells. Application of fluid shear stress was used to test the mechanical adhesion strength of cells on keratin coatings. The structure, biochemical stability and sustained cellular adhesion of these coatings support keratin’s capacity to provide a stable interface between POPs and skin. Side-by-side studies of extracted and recombinant keratins reveals that the recombinant form of these materials may provide distinct advantages for their use in POP devices. Overall, this study confirmed that a uniform, silane-coupled keratin coating was feasible. We demonstrated the substrates contain a biological function in terms of cellular adhesion and phenotypic changes in skin-relevant cells. These results support the biomimetic function of keratin on silanized Ti, which may provide a suitable coating to translate percutaneous medical device coating applications toward clinical use.

In recent years, space exploration has been driving studies that enable sustained human presence in space. In such studies, fluidics relating to biology have become important. Fluids in biological systems span from large-scale flows relevant to circulatory, digestion, and pulmonary systems, but also involve many micro-scale porous flows. Hence, space exploration is driving a novel need to characterize fluidics in microscales in microgravity conditions. In this work, we study the porous flow network within bones that stimulates cellular growth and has the potential to relate to osteoporosis (including driving osteoporosis in astronauts). To study this effect, computational fluid dynamics (CFD) simulations are performed on a microfluidic device with a hexagon structure and compared to experimental results in both normal gravity (1g) and microgravity (0g) via Blue Origin's New Shepard Vehicle (NS-23 attempt and NS-24 launch). CFD results have been created to predict the transport character of nutrients in the bones. These insights have the potential to lead to preventative measures for osteoporosis in astronauts.

This thesis project examined the interactive fluid dynamics between a blood pump and the univentricular Fontan circulation. 2-D particle image velocimetry (PIV) measurements were conducted on an idealized total cavopulmonary connection (TCPC) with an axial pump prototype in the inferior vena cava (IVC). Fluid velocity profiles were examined under various physiologic conditions for Fontan patients. The velocity profiles for all cases demonstrated the shunting of flow from the IVC toward the right pulmonary artery. A rotational component in the pump outflow was observed forcing flow to the periphery as compared to the flow profile without a pump present in the IVC. The inclusion of the pump provides a pressure rise of 3 to 9 mmHg. These results demonstrate the ability of the intravascular blood pump to support a Fontan circulation and support the continued optimization and development of the pump.

by Lau Man-fei and Leung Yip-shing. / Thesis (M.B.A.)--Chinese University of Hong Kong, 1988. / Bibliography: leaves 58-59.

Device-to-device (D2D) communications underlaying a cellular infrastructure takes advantage of the physical proximity of communicating devices and increasing resource utilisation. However, adopting D2D communications in complex scenarios poses substantial challenges for the resource allocation design. Meanwhile, matching theory has emerged as a promising framework for wireless resource allocation which can overcome some limitations of game theory and optimisation. This thesis focuses on the resource allocation optimisation for D2D communications based on matching theory. First, resource allocation policy is designed for D2D communications underlaying cellular networks. A novel spectrum allocation algorithm based on many-to-many matching is proposed to improve system sum rate. Additionally, considering the quality-of-service (QoS) requirements and priorities of di erent applications, a context-aware resource allocation algorithm based on many-to-one matching is proposed, which is capable of providing remarkable performance enhancement in terms of improved data rate, decreased packet error rate (PER) and reduced delay. Second, to improve resource utilisation, joint subchannel and power allocation problem for D2D communications with non-orthogonal multiple access (NOMA) is studied. For the subchannel allocation, a novel algorithm based on the many-to-one matching is proposed for obtaining a suboptimal solution. Since the power allocation problem is non-convex, sequential convex programming is adopted to transform the original power allocation problem to a convex one. The proposed algorithm is shown to enhance the network sum rate and number of accessed users. Third, driven by the trend of heterogeneity of cells, the resource allocation problem for NOMA-enhanced D2D communications in heterogeneous networks (HetNets) is investigated. In such a scenario, the proposed resource allocation algorithm is able to closely approach the optimal solution within a limited number of iterations and achieves higher sum rate compared to traditional HetNets schemes. Thorough theoretical analysis is conducted in the development of all proposed algorithms, and performance of proposed algorithm is evaluated via comprehensive simulations. This thesis concludes that matching theory based resource allocation for D2D communications achieves near-optimal performance with acceptable complexity. In addition, the application of D2D communications in NOMA and HetNets can improve system performance in terms of sum rate and users connectivity.

Device-to-Device (D2D) communication is one of the technologies for next generation communication system. Unlike traditional cellular network, D2D allows proximity users to communicate directly with each other without routing the data through a base station. The main aim of this study is to improve the overall energy efficiency (EE) of D2D communications overlaying cellular system. To reduce the complexity of joint EE optimization, we decompose the main EE problem into two subproblems; resource efficiency (RE) optimization in the first stage and EE optimization for D2D pairs in the second stage. Firstly, we propose an alternative two-stage RE-EE scheme for a single cellular user equipment (CUE) and a D2D pair utilizing uplink spectrum. Later, we extend this work for multiple CUEs and D2D pairs by considering the downlink orthogonal frequency division multiple access (OFDMA). By exploiting a range of optimization tools including the Bisection method, interior point algorithm, fractional programming, Dinkelbach approach, Lagrange dual decomposition, difference of convex functions, and concave-convex procedure, the original non-convex problems are solved and we present iterative two-stage RE-EE solutions. Simulation results demonstrate that the proposed two-stage scheme for uplink scenario outperforms the cellular mode and dedicated mode of communications and the performance is close to the global optimal solution. The results also show that the proposed schemes for downlink resource sharing provide improved system EE performance with significant gain on EE for D2D users compared to a two-stage EE-EE solution, which is obtained numerically. Furthermore, the RE and EE optimization for non-orthogonal multiple access (NOMA) are considered to study the effect of users' access to the whole spectrum. The results indicate that the proposed RE scheme for NOMA with D2D communications achieves higher system EE compared to the OFDMA based schemes.

Mobile devices equipped with features (e.g., camera, network connectivity and media player) are increasingly being used for different tasks such as web browsing, document reading and photography. While the portability of mobile devices makes them desirable for pervasive access to information, their small screen real-estate often imposes restrictions on the amount of information that can be displayed and manipulated on them. On the other hand, large displays have become commonplace in many outdoor as well as indoor environments. While they provide an efficient way of presenting and disseminating information, they provide little support for digital interactivity or physical accessibility. Researchers argue that mobile phones provide an efficient and portable way of interacting with large displays, and the latter can overcome the limitations of the small screens of mobile devices by providing a larger presentation and interaction space. However, distributing user interface (UI) elements across a mobile device and a large display can cause switching of visual attention and that may affect task performance. This thesis specifically explores how the switching of visual attention across a handheld mobile device and a vertical large display can affect a single user's task performance during mobile interaction with large displays. It introduces a taxonomy based on the factors associated with the visual arrangement of Multi Display User Interfaces (MDUIs) that can influence visual attention switching during interaction with MDUIs. It presents an empirical analysis of the effects of different distributions of input and output across mobile and large displays on the user's task performance, subjective workload and preference in the multiple-widget selection task, and in visual search tasks with maps, texts and photos. Experimental results show that the selection of multiple widgets replicated on the mobile device as well as on the large display, versus those shown only on the large display, is faster despite the cost of initial attention switching in the former. On the other hand, a hybrid UI configuration where the visual output is distributed across the mobile and large displays is the worst, or equivalent to the worst, configuration in all the visual search tasks. A mobile device-controlled large display configuration performs best in the map search task and equal to best (i.e., tied with a mobile-only configuration) in text- and photo-search tasks.

Device-to-device communication has been suggested as a complement to traditional cellular networks as a means of offloading cellular traffic. In this thesis we explore a solution for device-to-device communication based on opportunistic content distribution in a content-centric network. Communication opportunities arise as mobile nodes roam around in an area and occasionally enter in direct communication range with one another. We consider a node to be a pedestrian equipped with a mobile device and explore the properties of opportunistic communication in the context of content dissemination in urban areas. The contributions of this thesis lie in three areas. We first study human mobility as one of the main enablers of opportunistic communication. We introduce traces collected from a realistic pedestrian mobility simulator and demonstrate that the performance of opportunistic networks is not very sensitive to the accurate estimation of the probability distributions of mobility parameters. However, capturing the space in which mobility occurs may be of high importance. Secondly, we design and implement a middleware for opportunistic content-centric networking, and we evaluate it via a small-scale testbed, as well as through extensive simulations. We conclude that energy-saving mechanisms should be part of the middleware design, while caching should be considered only as an add-on feature. Thirdly, we present and evaluate three different energy-saving mechanisms in the context of opportunistic networking: a dual-radio architecture, an asynchronous duty-cycling scheme, and an energy-aware algorithm which takes into account node selfishness. We evaluate our proposals analytically and via simulations. We demonstrate that when a critical mass of participants is available, the performance of the opportunistic network is comparable to downloading contents directly via the cellular network in terms of energy consumption while offloading large traffic volumes from the operator. / <p>QC 20151120</p>